My First Li-Po Experience

[dj_ski69]

Hey all,
I have finnaly received my first shippment of Li-Po's last week...
I bought them From MAXAMPS...They are the maxamps label Hyperion cells/taps....I got 2 8000's(7.4v), 1 6000(7.4), and 1 2100mah(11.1v) packs....
Also I got the new LBA6 Balancer from Hyperion(figured I'de stay with one brand) and it makes taking care of the li-po's very easy....
So far I absolutely love these batts....enough to have already begun to give away my normal ni-mh packs....;)
Yeah, yeah, so I spent 500 bux on these things....WELL WORTH THE MONEY...
My Mini Inferno ST with a HI-MODEL 4000kv BL motor and this 11.1v 2100mah pack is just rediculously a fast little bugger....Probably the truck i have my most fun driving now....
The 6000mah pack is for my FT T4....Haven't even run it yet, too wrapped up into my MI ST at the moment....

The 8000's I am saving for a VERY speacial Stadium Truck thats being built now...(more on this when the time is right).....but....
I decided to test out the 8000mah packs my putting them under a load of 35 amps and measuring the run time down to a very conservative 6.0v cut-off(3v/cell).....
At the same time I wanted to test out how much capacity i would lose if i let one sit for 24 hours after charging it.....SO...
I charged one up, then 24 hours later I charged the other....Then I tested em both....
Unbelievable.....Batt # 1 (24 hours idle time) ran to 18 minutes 30 secs....
Batt # 2 (fresh charge) ran 18 minutes 31 secs.....
Awesome performance.....
Both packs avg voltage was way above that of my IB3800 packs.....
just unbelievable....

Really...IF you don't already have Li-po's....then get em....
I don't know what other brand Li-Po's are like but these Hyperions are just great in my own experience...

Peace

SkI

[tcolesen]

Awesome, another Lipo convert! Just so you know 3v/cell isn't conservative anymore, that's now the standard. Some airplane guys are even pushing LVC to 3.3v/cell with the newer 20C cells.

[Brian23]

500 dollars on lipos!! alot there

[LaBrother]

I also just got some maxamps lipos. I got two 4S 4000mah packs, i use them in parallel in an 1/8 scale truck. Great batteries, awesome performance

[schenck77]

good to see more people trying out lipo's. I picked up one of there 8000mah packs last week but haven't been able to test it out yet. I was already running lipo's I just wanted to get a higher mah pack then what I was running.

[Craps]

I can remember 2 1/2 years ago I was the only one here telling everybody this samething and got bashed on alot. Now there is alot of converts spreading the news!

Now if the Pro Truck class will take off nation wide with a 1/10th scale 2wd stadium truck with any motor and any battery with a 20 minute main!!!

Pro Truck is a great class with no battery wars, no motor zapping, no battery zapping, no comm cutters if you run brushless with low maintence and lots of track time to better those skills!!!!!

The future is here with li-pos and brushless!!

[scoob]

I remember when somebody was nice enough to let me borrow a li-po pack in my first pro-truck race, and I thought "well, those things are expensive and dangerous but if he's going to let me try it, why not". I was hooked! Everything I read about li-po being SO DANGEROUS was wrong. You just have to treat them with respect.

I have no doubt that I would not enjoy RC as much today if I hadn't discovered li-po.

[enricopalazzo]

what am i looking at guys for eithe 4000mah or 6000mah 7.4v lipos, and if they will work with a novak gtb 5.5?
thanks

[nicholcgn]

I run some 4400's from polyquest with my t4 and the 5.5. You are pushing the limit of what you want to run. I would recommend a 6000 battery. The extra practive time would be nice and you would see less stress. My batteries are slightly warm. I am going to some 8000 soon.

[dj_ski69]

what am i looking at guys for eithe 4000mah or 6000mah 7.4v lipos, and if they will work with a novak gtb 5.5?
thanks
The best thing I can tell you is go with the 6000mah pack and get the Hyperion LBA6 Balancer....
The only thing you have to worry about is over discharge....
My U-Force 75 is PC programmable and I can set the Cuttoff Voltage at my leisure.....
The Novak systems do not have this capability and you need to be carefull with that....You can get LVC devices to hook in-line between you battery and the Speedo.....This will work perfect for your setup....
Also the 6000mah pack gives you more room for error on runtime and LVC...

SkI

[khyron]

I'm excited to find someone who's purchased multiple li-po packs from MaxAmps and is pleased with them. I'm interested in doing the same, but I have a couple questions that hopefully someone viewing this thread can answer.

First of all, I intend to use these packs with a Novak GTB, which lacks any low voltage cutoff (as far as I know). I have been looking around for a LVC device which comes preset to 6.0v but have not been able to find one. Can anyone point me at one? I'm not looking for a device that lights up an LED at 6.0v and I'm not looking for a device that's preset to cut off at 5.3v but can be "programmed" to cut off at 6.0v, I'm looking for a device that cuts off at 6.0v plain and simple (fairly idiot proof). I want to keep expensive batteries safe.

Second, I'm a little confused by all this talk of balancing and balancers. In reading up on another li-po option, the Team Orion Platinum 4800 (more expensive than the MaxAmps packs, I know) I thought I understood that "balancing" a li-po pack was simply a matter of charging the cells independantly (instead of together in parallel) every once in a while to keep the pack healthy. However I also see "balancer" devices sold at places like MaxAmps. What does a "balancer" do exactly? If my understanding of what balancing does is correct, why does one need a balancer, why not just charge using the individual cell taps now and then like people do with the Orion pack? If my understanding of balancing is incorrect, can someone help me understand it better?

Third, can anyone point out anywhere on the MaxAmps site or elsewhere for someone to learn what the different "taps" they offer are, where they are on the packs, and what they look like, etc.? It's a little daunting to order an expensive battery pack and make those sorts of decisions without knowing what's really involved.

Fourth, and finally, since there are no high resolution photos on the MaxAmps web site anyplace, can anyone who actually has a pack in their hand tell me exactly what it looks like? My understanding is that the Orion pack is a brick because it's made of prism shaped cells containing a gel electrolyte which is safer in collisions or overdischarge situations because it expands to break connectivity. My understanding is that some other li-po cells are cylindrical, and contain fluid electrolyte, and are thus a little (in the wrong circumstances) less safe. I'm NOT bashing these kinds of cells at all, I just want to understand which sort of cells the MaxAmps packs are made of, that's all.

I'm eagerly considering ordering some 6000mah packs from MaxAmps (because they appear to be the highest capacity li-po they sell that isn't larger than a standard battery pack) and am just looknig for some more details. Thanks very much in advance to anyone who can help me out. :)

[enricopalazzo]

To add to the conversation: Can anyone please tell me what voltage they are getting out of a Fully Charged Maxamps 7.4v 6000mah pack.

Thanks

[chilledoutuk]

4.2v per a cell

[tcolesen]

khyron,
Look at this LVC:
http://66.241.195.91/lithium/lithium.asp?path1=lithium
A balancer does just what its name suggests, it balances the voltages of the individual cells in a pack. It does this by monitoring the voltages of each cell, and if (a) cell's(s') voltage(s) is(are) higher, then it puts a load on the cell(s) that have higher voltage(s), to bring them down to the level of the lower voltage cells.
You could charge each individual cell, but using a device that does a similar process for you is easier and less time consuming. For example, if you use a 4s Lipo pack (this is the only size I use), then you would have to charge 4 individual cells. For a 2s pack, this would be an easier option.


Third, can anyone point out anywhere on the MaxAmps site or elsewhere for someone to learn what the different "taps" they offer are, where they are on the packs, and what they look like, etc.? It's a little daunting to order an expensive battery pack and make those sorts of decisions without knowing what's really involved.

All Lipos are prismatic (rectangular) cells. Depending on the cell configuration (and size), there will be multiple cells stacked on top of each other, and through the tabs (not taps) the cells are connected together. A Maxamps 2s 6000mah pack is composed of four 3.7v 3000mah cells in a 2s2p configuration, where there are two sets of 3.7v 6000mah "bricks" that are then put in series. All that you would see on the outside is the black shrinkwrap covering the pack, with the power wires and taps exiting the same side of the pack. The tap connector choice depends on which balancer you will be using. If you plan on using the Hyperion LBA6 balancer, then get the Hyperion taps. If you plan on using a TP-205 balancer, then you would get TP taps. On Maxamps website, there is an option for this located under the price of the pack.
Lipos are not made into cylinders (that I am aware of), but Li-Ions are. The plastic cover on the Orion pack is nothing more than a thicker version of the shrink wrap that is standard on Lipo packs. Its purpose is to provide more protection to the cells during crashes and when rocks hit the battery so that the pack is less likely to be damaged. This plastic case isn't really necessary, since one should not put a Lipo in such a situation where it would need a case like that.
Cylindrical Li-Ion cells can be more safe than Lipo, since they usually have vents on the positive end of the cell, so instead of going up in flames or puffing, it will just vent out gases. These cells are also safer because they have a metal case that can't become damaged like the "pouch" of a prismatic cell. Just FYI, there are also prismatic Li-Ion cells, and they are mainly used in things like cell phones, PDAs, and other small consumer electronics.

[khyron]

khyron,
Look at this LVC:
http://66.241.195.91/lithium/lithium.asp?path1=lithium


Thanks, that appears to pulse the motor and "sense" the cutoff voltage based on the starting volatge. What I'm really looking for is something that cuts off at 6.0 volts. There's gotta be one out there, I just need to find it...


A balancer does just what its name suggests, it balances the voltages of the individual cells in a pack. It does this by monitoring the voltages of each cell, and if (a) cell's(s') voltage(s) is(are) higher, then it puts a load on the cell(s) that have higher voltage(s), to bring them down to the level of the lower voltage cells.
You could charge each individual cell, but using a device that does a similar process for you is easier and less time consuming. For example, if you use a 4s Lipo pack (this is the only size I use), then you would have to charge 4 individual cells. For a 2s pack, this would be an easier option.

Much appreciated. I can see how aviation folks and others who use higher voltage (more cells in series) packs would benefit from a balancer in terms of convenience. For me, using strictly 7.4v packs which are commonly 2s. it wouldn't make much difference I guess.

[tcolesen]

Check the post again. I did an edit to answer your other questions.

The LiSaver operates differently than you think. It does cut based on the starting voltage, but through the voltage it reads it is able to determine the cell count of the pack, like 6-8.4v for a 2s pack. With this information, it sets the cutoff to 3v/cell times the number of cells it detects. So, for a 2s Lipo it'll cut off at 6v, no matter the starting voltage (as long as it's in the range of 6-8.4v). It will do the same for any cell count Lipo pack.
All LVCs except for the fixed cutoff voltage ones operate in this same manner. To get a fixed LVC for 2s is completely unnecessary; an automatically adjustable one will act in the same manner and will be very close to the same price as the fixed one.

[khyron]

Check the post again. I did an edit to answer your other questions.

The LiSaver operates differently than you think. It does cut based on the starting voltage, but through the voltage it reads it is able to determine the cell count of the pack, like 6-8.4v for a 2s pack. With this information, it sets the cutoff to 3v/cell times the number of cells it detects. So, for a 2s Lipo it'll cut off at 6v, no matter the starting voltage (as long as it's in the range of 6-8.4v). It will do the same for any cell count Lipo pack.
All LVCs except for the fixed cutoff voltage ones operate in this same manner. To get a fixed LVC for 2s is completely unnecessary; an automatically adjustable one will act in the same manner and will be very close to the same price as the fixed one.

All excellent and detailed information, thanks so much! I really wish such details were more readily available on the battery assembler/reseller websites, but with so many helpful forums I guess it doesn't matter. It does kind of amuse me though that Team Orion sells the most hyped and most expensive (dollars/mah) li-po there is and they don't even link to their own FAQ about it anyplace, include it on their products page, or even register it in their search engine. You have to find your way to their FAQ from other sites! Bonkers.

The 6000mah (and lower) packs from MaxAmps intruige me greatly, because they are potentially slightly smaller than the Team Orion pack and I am interested in sticking the batteries I buy into a T2. I would really like to avoid or minimalize modification to its rear bulkhead, which the Team Orion pack absolutely requires. I don't suppose, has anyone here tried to fit a MaxAmps pack in a T2 by any chance?

[Tomka]

Could someone with hands on experience please tell me the approximate runtime I can expect from a 6000mah 7.4V Maxamp lipo with a Novak GTB 4.5 or 5.5. I'll be running this setup in a TC4

[TimisTim]

I run mine in a xxx-t MF1 with alot of aluminum on it. Its running a Feigao 8S and UF75 controller geared 19/86. I get ALOT of run time on these batts maybe 20-25 minutes. In fact I have used this on many occasions in my MT2 running a 7L with Maxx sized wheels and they can handle the amp draw fine. I just ordered another today so I can hook them up in series to make a 4S 6000 pack.

[tucsonbroker]

I visited maxamps.com and read a little bit about LIPO batteries. To be honest, there are a couple things keeping me from getting some.
1. Charge times. If it takes 1 hour to charge the battery for a 20 min run time, I don't think that's worth it.
2. Battery care. I don't want to have to worry about them blowing up or catching fire. The part about having a fireproof box to charge and store them is a little scary. The nice part about the NMH batteries is zero maintenance and risk.
3. Added equipment. Special charger, special balancer, special limiter. I'm not concerned about cost, just a bunch more crap to have.

Comments?

[khyron]

I visited maxamps.com and read a little bit about LIPO batteries. To be honest, there are a couple things keeping me from getting some.
1. Charge times. If it takes 1 hour to charge the battery for a 20 min run time, I don't think that's worth it.
2. Battery care. I don't want to have to worry about them blowing up or catching fire. The part about having a fireproof box to charge and store them is a little scary. The nice part about the NMH batteries is zero maintenance and risk.
3. Added equipment. Special charger, special balancer, special limiter. I'm not concerned about cost, just a bunch more crap to have.

Comments?

Yeah, one - what planet are you getting your NiMH batteries from that they have a significantly better runtime to charge ratio than 60 minutes charge to 20-25 minutes runtime? Can you charge for a 5 minute run in well under 11 minutes?

LiPo batteries require less maintenance not more. They don't become pretty much useless after 20 or 30 cycles. They don't need to be discharged, ever. They don't need to be conditioned or zapped. You have a point about "special" charger but only if you want to buy one, plenty of chargers exist that charge both types of cells (I think any "one kind of battery" charger is pretty lame, personally). As for balancing, you don't need a "balancer" at all really. They are just a convenience. You can balance your pack with your charger, simply by charging each of the two cells in a 7.4v pack individually every once in a while (how often is up to you).

If you're afraid of using something because it requires following directions to be safe, then there are a lot of things you might want to stop using. The "these things will explode and kill you if you look at them wrong" misunderstandings that exist about LiPo batteries have a lot less to do with reality and a lot more to do with 1) rabid rumormongering, 2) lawyer style writing by scared retailers, and 3) confusion between older aircraft style cells and what people are using in cars right now.

[tucsonbroker]

Yeah, one - what planet are you getting your NiMH batteries from that they have a significantly better runtime to charge ratio than 60 minutes charge to 20-25 minutes runtime? Can you charge for a 5 minute run in well under 11 minutes?


My car is stock, I get 15 minutes run time off a 45 minute charge. That's a 1:3 ratio. Unless I can achieve a significantly better ratio, then the added cost doesn't make sense.



LiPo batteries require less maintenance not more. They don't become pretty much useless after 20 or 30 cycles. They don't need to be discharged, ever. They don't need to be conditioned or zapped. You have a point about "special" charger but only if you want to buy one, plenty of chargers exist that charge both types of cells (I think any "one kind of battery" charger is pretty lame, personally). As for balancing, you don't need a "balancer" at all really. They are just a convenience. You can balance your pack with your charger, simply by charging each of the two cells in a 7.4v pack individually every once in a while (how often is up to you).

If you're afraid of using something because it requires following directions to be safe, then there are a lot of things you might want to stop using.


No need for sweeping generalizations. This is a battery, not a dangerous piece of machinery. Batteries are not _typically_ a dangerous household item, like a knife or drano. A battery isn't normally something which requires, "a fire-safe container" or that I "keep a dry fire extinguisher nearby" or that I abide by special "discharging rules".


The "these things will explode and kill you if you look at them wrong" misunderstandings that exist about LiPo batteries have a lot less to do with reality and a lot more to do with 1) rabid rumormongering, 2) lawyer style writing by scared retailers, and 3) confusion between older aircraft style cells and what people are using in cars right now.

I'm not sure where I said that they will explode and kill me if I look at them wrong, but you are welcome to your interpretation. All of the information above was taken directly from the maxamps.com site. While it appears that it is written to cover themselves legally, there is something to be said for knowing the risks in advance. That would be like picking up a knife or using draino without reading the instructions.

Now I realize that idiotic lawsuits, like the McDonalds hot coffee lawsuit, are changing the legal landscape, but just because they are covering themselves doesn't mean that you can disregard what they say. It still hurts when you spill hot coffee on your lap.

[khyron]

My car is stock, I get 15 minutes run time off a 45 minute charge. That's a 1:3 ratio. Unless I can achieve a significantly better ratio, then the added cost doesn't make sense.

I think where people tend to strongly prefer lithium polymer technology is that over the course of the discharge cycle, they tend to run pretty flat on voltage and then just drop at the end where the power output on other kinds of cells drops off more gradually. You may have a really great pack with amazingly flat performance, but for a lot of folks getting 15 minutes out of something where only the first 10 are really consistent feels more like a "10 minute runtime" so I guess there's a lot in interpretation.

[tucsonbroker]

Back to the safety issues, what are people doing? My intent is to become informed, but understand the practical use.

1. Are you charging and storing in fire safe containers? What do you use?
2. Are you always around for charging?

[nicholcgn]

You will get several benefits from a lipo. One the punch is out of this world. NIMH can not compare. I believe this is due to internal resistance.
If you do not completely discahrge you battery in a run and it is not very warm you plug it in and charge it back up. This does not hurt the battery.
You can run this battery multiple times in a day. No issues with this. There is a large weight advantage. You can also get runtimes in the 12000 mah battery range of over 30 mins.

Charge times are 1c at this time. I know with gp3300's you can get a 5 amd charge. With a 6000 mah on lipo you get a 6 amp charge. Simple math says you are getting more runtime per charging minute. It takes an hour becuase you have a lot more mah. mah tell you the energy in the battery. So any batteries with the same mah - 4400 lipo and a 4400 minh will give you almost the same exact runtime. Difference will be speed and grunt from my experience. NIMH more speed initially but will fall below the lipo fairly quickly. Grunt or torque is hands down advantage of the lipo. Almost seems like another cell.


Are there some downsides? Yes you need to be safe with them. This is the same as with other batteries of this type that you use. Cell phones are an example. You can make a cheap storage system for charging and storing.
Mine is a pyrex plate with a bag of sand on top of the batteries. If one was to discharge then it would melt the bag and the sand would put it out. Most issues come from the fact that people charge the battery incorrectly.
(Ever heard a NIMH battery go off? Can sound like a gun.) So far every example of an issue I have seen is someone who mischarged them or was intentionally overcharging to make a video of how dangerous they are. The issues that caused fires where when someone left them unattended.

If you are well over drawing on the amps can it ruin a battery - yep.

Are these for you - Nope. You have to many concerns. These types of concerns have been around for other batteries. Give them another 2 years and they will be ready for you. Until then watch the guys who run them have some great successes.

This is a NEWER tech for RC. If you do not want to take precautions then you can have problems. You should never charge any battery(lipo, nimh or others. Read the warnings on them also.) unsupervised but most people do. You are playing the lottery when you do. I love them and will never go back. I have had no issues in over 6 months. I run my stuff hard. I know some people that have been running them for over 2 years.

[Craps]

Nicholcgn
Nice post!!!

[chilledoutuk]

My car is stock, I get 15 minutes run time off a 45 minute charge. That's a 1:3 ratio. Unless I can achieve a significantly better ratio, then the added cost doesn't make sense.

My friend its all relative with my 4000mah kokam lipo i get about 25minute runtime with my hacker c40 8s whereas i would get maybe just about 12mins with a new gp3700 pack.
Now what this means to me is that if you are getting 15 minute runtimes with a stock setup with a segnificantly lighter and puchier kokam 4000mah pack or equivelent lipo would not only improve performance but likely double your runtime to 30mins.

Although i dont recomend using lipo with brushed motors i wouldnt like to see how hot they get after running for 30mins.

You have got to remmeber that the technology were using here is lithium polymer a lot of laptops,mobile phones,camcorders, have lithium ion cells which are more dangerous but becuase they are charged in a heavilly controlled manner they pose no obvious danger.
the same applies to charging these cells once you have done it a few times and established a system then there is very little that can go wrong just like the mobile phone you have charged over 150 times.

you could always buy a cheap barbecue and put your cells in there when your charging them and then in the summer use it to cook your steaks etc dual purpose. lol

[khyron]

If you do not want to take precautions then you can have problems. You should never charge any battery(lipo, nimh or others. Read the warnings on them also.) unsupervised but most people do. You are playing the lottery when you do. I love them and will never go back. I have had no issues in over 6 months. I run my stuff hard. I know some people that have been running them for over 2 years.

I seriously don't get why people are so darn fearful of these things. It's not like they're significantly more dangerous than any other form of high current battery if used incorrectly. You can make a NiCd or NiMH explode if you want to, or use it to start a fire. You can do that with a can of Pactra spray paint too. Heck if you manage to screw up your automobile's battery through abuse or negligence you can create a nice bubble of hydrogen under your hood and do a good number on anyone stupid enough to be smoking when lifting the hood. None of that's new, but we're not afraid or driving, painting bodies, or using other batteries. So what is the deal?

Are people who are heavily invested in other stuff just mad? Sometimes I wonder. It seems like the anti-lipo sentiment is sometimes just a little like the anti-brushless sentiment. "Damn it, I spent tons of money and I deal with higher maintenance and more limitations and you should too!"

Caution? Fear? Hazing? FUD? I guess it's all in opinion...

[Craps]

I seriously don't get why people are so darn fearful of these things. It's not like they're significantly more dangerous than any other form of high current battery if used incorrectly. You can make a NiCd or NiMH explode if you want to, or use it to start a fire. You can do that with a can of Pactra spray paint too. Heck if you manage to screw up your automobile's battery through abuse or negligence you can create a nice bubble of hydrogen under your hood and do a good number on anyone stupid enough to be smoking when lifting the hood. None of that's new, but we're not afraid or driving, painting bodies, or using other batteries. So what is the deal?

Are people who are heavily invested in other stuff just mad? Sometimes I wonder. It seems like the anti-lipo sentiment is sometimes just a little like the anti-brushless sentiment. "Damn it, I spent tons of money and I deal with higher maintenance and more limitations and you should too!"

Caution? Fear? Hazing? FUD? I guess it's all in opinion...

Damn good post and could not have said it better myself! I have always said the non-li-po and non brushless companies that have the most to loose from lost sales are behind the anti-propanganda! It is all about greed from some of the big names in the business!

Honestly nickel batteries are MORE DANGEROUS because they explode without any pre warning what so ever and throw HOT metal casing like shrapnel from a grenade!!!! I got rid of all of those dangerous nickel batteries!!! LOL!!!!

[Muck]

Fear is a good thing, it keeps you alive! Being fearful makes you want to learn the proper ways. It's the people that aren't fearful that pose the greatest threat to themselves and to others.

[tcolesen]

Great posts from all! Just a little to add.

Lipo batteries are inherently dangerous. By using them, you are somewhat taking a risk. That risk can be greatly minimized when these batteries are used with devices that will not allow them to reach the "red" zone. These devices include 2 VERY simple ones - a balancer and a LVC device. Most balancers are no-brainers. You simply plug them into a pack with the appropriate taps, and charge away! Some balancers have heavy documentation on what various LED flashes or different beeping sequences mean, but these are put there to inform the user of any possible dangers (to improve safety). An LVC device is quite necessary. It will keep the cells from reaching low voltages that have been known to cause Lipos to combust. Even if a pack that has gone below the 3v/cell mark doesn't show any physical damage (like puffing), there can still be internal damage that could decrease the safety and performance of the battery.

By not using these two tools (or a similar form of them), safety is something to worry about. For example, let's take a 3s Lipo pack. Naturally, the cells in this pack are not exactly the same, and will have [slight] variations in capacity and internal resistance. If this pack were to go out of balance, the imbalance would most likely become worse. Generally an imbalance of greater than 0.05v is concerning, since 4.25v is considered the "stable" upper voltage limit during a charge. By charging an imbalanced pack, there can be internal damage in the cell(s) that charge(s) to a higher voltage. Over time, this internal damage can lead to puffing, and possibly to combustion, as the cell(s) are pushed out of their "comfortable" voltage limits.

I don't mean to scare anyone; I am merely describing a somewhat worst-case scenario when certain safety precautions are overlooked. My advice is that if you don't have one or the other (or both), then get a LVC device (not an audible one, but one that can cut the throttle) and a balancer.

Okay, I'm done :).

[scoob]

My car is stock, I get 15 minutes run time off a 45 minute charge. That's a 1:3 ratio. Unless I can achieve a significantly better ratio, then the added cost doesn't make sense.



I don't no I thought you were supposed to let NIMH batteries cool before you run them. I always do and it takes at least 30 more minutes because the stupid things get so warm. 1:5 ratio for me. Also, I run 8000 mah LI-PO packs and charge at 8 amps. When I'm at the track I easily get a 1:2 ratio. Actually I think it's better than that. :)

LI-PO doesn't get hot at all after charge and you can disconnect the pack and run it right then and if you get one of the packs that can handle high current draw (like the 8000s), or your setup doesn't stress the pack, it won't be hot after a run which means you can hook it up to the charger right after a run. You don't have to discharge it, wait for it to cool or put it in some wierd tray and do a rain dance for it to perform consistently strong. There is a big difference to me :)

[nicholcgn]

I see more runtime also on the same pack. But some of the increased runtime comes from the decrease in weight. This has noting to do with the mah rating of the battery but just a rule of physics. So if you added wight to the cars so the weigh the same you would see less differences. I believe the other piece fot the equation is IR. But because I never want to run my lipos near their cutoff I lose some actual mah from use. That is my choice though. In theory I am seeing a good bit of extra runtime. I just do not want to mislead people. If you lightned the car with NIMH up as much you would see increased runtimes. Also a lot of people also go brushless at the same time the go to lipo.

Would be nice if someone who makes lipos or deals with batteries would tell us what we could expect if a lipo and a nimh were powering the same exact weight if there is a difference in runtime. And why.

[SpEEdyBL]

nicholicn,

If total battery resistance, weight, voltage and capacity were the same, you would theoretically get the same runtime. Maybe the nature of the chemistry of the battery will have an effect on this. That I don't know. I do know that most lipos have less resistance than ni-mhs of the same capacity/voltage and that allows for more power to be supplied to the motor and less to be converted into heat. How the extra available power is used depends on the users preferences. So yes, it is possible to get more runtime and still have the same watts power output.

To all,

One thing that hasn't been mentioned in this thread is that you need a LVC that measures individual cell voltage if you are to use a balancer. The danger in using a balancer (during charging) and not using such LVC is that the balancer will supply more charge to the cells that have slightly higher capacities. When discharging, the cells with less capacity will dump first and they may drop below a safe voltage before a normal LVC, which detects voltage across the entire pack, will detect low voltage. E.g. If you have a 3s pack, and one of the cells has less capacity than the other two, it will dump first and the voltage of each of the cells may read 2.6,3.2,3.2. The total voltage is 9 volts, which is where a standard LVC would cut off, but one is already close to the danger zone. An LVC that detects individual cell voltage would cut the voltage before it's too late.

[chilledoutuk]

I see what your saying speedybl and thinking about it your right it would be best to everynow and then discharge all your cells to 3v each cell and then charge them as a pack that way they would all contain the same power.

thanks for pointing this out spedybl

[chilledoutuk]

Just thought i would mention that some time ago somone was saying that you dont have to charge lipos to 4.2v per a cell and that charging to a lower voltage can be easier on the cells.

[khyron]

Just thought i would mention that some time ago somone was saying that you dont have to charge lipos to 4.2v per a cell and that charging to a lower voltage can be easier on the cells.

If you didn't charge a lipo cell to 4.2v, you wouldn't be reaching nearly the full capacity of the cell, ever. Nobody would really be interested in doing that, I don't think...

I think you might be confusing volts with amps. It's been suggested that you can charge lipo cells at a rate less than 1C but that "C" doesn't mean "cell". It refers to the charge rate, it's a simple way of saying "charge a 4800mah pack at 4.8 amps" or "chrage a 8000mah pack at 8 amps" without knowing how much capacity the a given pack has.

HTH.

[SpEEdyBL]

It is in fact batter for the cells not to charge them to 100% capacity. It's best to charge them to 90% capacity. Some say 80%, but in my opinion, that would take too much from your runtimes. It think 90% is when the cell first reaches 4.2 volts at 1C. 100% is when the cell is 4.2 volts after the charge rate reduces 0 amps.

[khyron]

It is in fact batter for the cells not to charge them to 100% capacity. It's best to charge them to 90% capacity. Some say 80%, but in my opinion, that would take too much from your runtimes. It think 90% is when the cell first reaches 4.2 volts at 1C. 100% is when the cell is 4.2 volts after the charge rate reduces 0 amps.

Either you or I is confused about how CC/CV charging works and lipos work, so I'll wait to see what someone else says. It's my understanding however (I guess I could be wrong) that the point at which 4.2 volts is reached during a proper lipo charge is not "90%" done, but sooner and that charging a lipo to 100%, if you're about to use it, is completely harmless. The only "80%" I've seen is in descriptions of discharging (using) lipos and storing them.

[tcolesen]

I see what your saying speedybl and thinking about it your right it would be best to everynow and then discharge all your cells to 3v each cell and then charge them as a pack that way they would all contain the same power.

thanks for pointing this out spedybl

Lipo cells don't work like NiMh at all. If you were to discharge all the cells to 3v, then when you charge them there would be pretty large imbalances. Lipos should only be balanced at about 3.8v or higher.

Either you or I is confused about how CC/CV charging works and lipos work, so I'll wait to see what someone else says. It's my understanding however (I guess I could be wrong) that the point at which 4.2 volts is reached during a proper lipo charge is not "90%" done, but sooner and that charging a lipo to 100%, if you're about to use it, is completely harmless. The only "80%" I've seen is in descriptions of discharging (using) lipos and storing them.

It is my understanding the CC charges to about 90%. FMA direct says that you can charge to 90% using a 3C charge in only 20mins. That would mean that at a 1C charge in the CC mode it would be more like 95%. You're right, it doesn't really do any harm by charging them to 100%, it just takes longer to charge (CV).

BTW, storage should be at about 50-60% capacity, or ~3.8v/cell.

[chilledoutuk]

however the problem pointed out by SpEEdyBL stands if you were to charge the cells seperatly to 4.2v they might have different storage capacity in mah and thus when discharged one cell may dump before the other.

personally this is not much of an issue as i dont see the point in running down yoru lipo all the way to 3v a cell for many reasons.
1. if your pack is inbalanced then you may discharge one of the cells lower than 3v
2. when the voltage starts getting that low the performance will suffer and thus you may as well stop and recharge.
3. you probably will get bored after 15 mins of driving anyways.

[SpEEdyBL]

Lipo cells don't work like NiMh at all. If you were to discharge all the cells to 3v, then when you charge them there would be pretty large imbalances. Lipos should only be balanced at about 3.8v or higher.

BTW, storage should be at about 50-60% capacity, or ~3.8v/cell.

The point is, you want all the cells to dump at the same time when you are using an LVC that does not detect individual cell voltage. Otherwise it's best to have them balanced at full charge.

[tcolesen]

Another option is to use a LVC with a cutoff higher than 3V/cell. MGM uses a 3.1v/cell cutoff, which is very nice. IMO, overcharge is worse than overdischarge, since at 4.25v (0.05v over CV voltage), the cells can become unstable. At 2.95v, the damage would be less, especially if that's the voltage under load.

If you can get a system that monitors each cell's voltage, then by all means, use it!

[khyron]

If you can get a system that monitors each cell's voltage, then by all means, use it!

Can anyone reccomend a device that can do this? It would have to be a pretty simple thing for an R/C car application, since there are only two cells. ANyone make such a thing? Something that presumably plugs into the "taps" and cuts off the ESC completely once either of them hits, say, 3.0v?

(personally I think lights and buzzers are silly, I'd want a cutoff)

[SS Pede]

I've got a question also. What sort of balancer would work with the Orion pack? It looks like the pack just has a single round hole in the case that something plugs into. I haven't noticed this type of port on other lipo packs...usually it's a multi-pin plug or something like that. What gives?

[tcolesen]

I've got a question also. What sort of balancer would work with the Orion pack? It looks like the pack just has a single round hole in the case that something plugs into. I haven't noticed this type of port on other lipo packs...usually it's a multi-pin plug or something like that. What gives?

Do you know what size plug the "single round hole" takes? You could probably just use 4mm banana plugs, like you do for the battery's main output, and then you could charge the individual cells by using the single connector. You could probably even used the supplied cable to plug into the single connector!

Can anyone reccomend a device that can do this? It would have to be a pretty simple thing for an R/C car application, since there are only two cells. ANyone make such a thing? Something that presumably plugs into the "taps" and cuts off the ESC completely once either of them hits, say, 3.0v?

(personally I think lights and buzzers are silly, I'd want a cutoff)

The only device I know of that monitors individual cell voltage that is a single unit and is readily available is this one:
http://fmadirect.com/Detail.htm?item=2046&section=38

Instead of using that you could buy two separate LVC devices that are manually/automatically adjustable that work with single cells, and daisy-chain them together (connect their receiver cables together in series, but have each one's battery monitoring wires go to one cell).

[SS Pede]

I don't know the details about the port because I don't actually own an Orion lipo, or any lipos. I was under the impression that there was some device (balancer) to plug in that would discharge the appropriate cell to even out the voltage. There's a picture of the port in a recent issue of RCCA, but they don't say what exactly you would balance the pack with. They just say that balancing only affects run time, not voltage.

[khyron]

http://www.fmadirect.com/Detail.htm?item=2117&section=45 (different one)

Now this device seems to be the "perfect" answer if I understand how it works correctly from the product description at FMA (the photo on their site appears to be missing one of the leads coming out of the device, I've e-mailed them to make sure of that and am waiting for a response).

The description makes it sound like this device goes in-line with the throttle channel of the radio (more desirable, smarter location IMHO) rather than in line with the main power off the pack (less desirable, plus current pass-thru concerns under heavy load and cuts all power not just throttle). It also connects to the battery pack's "tap" or "node" connector and monitors cells individually. When any one cell reaches approaches a dangerous discharge level, it pulses the throttle for a (user programmable either 30 or 60 second) brief period and then cuts throttle completely. The only detail they leave out is where that cutoff is but as this device is totally lipo specific I'm guessing/hoping it's hard set to 3.0v?

Seems pretty darn perfect to me...

[tcolesen]

khyron, most LVCs that aren't the LED/buzzer type do go in line with the throttle channel and pulse the motor when the voltage gets to a certain point. That CellPro discharge protection device doesn't state what voltage it cuts/pulses at, so for all we know it could be 2.75v.

[khyron]

khyron, most LVCs that aren't the LED/buzzer type do go in line with the throttle channel and pulse the motor when the voltage gets to a certain point. That CellPro discharge protection device doesn't state what voltage it cuts/pulses at, so for all we know it could be 2.75v.

I said I hoped, I'm going to write to FMA to find out. Meanwhile, since you seem to have found a lot more of these devices than I have, would you mind pointing one out that goes in-line with the throttle channel, monitors both cells individually, and pulses and then cuts off at 3.0v? That would totally make my day. :)

[FLYBOY7]

just fyi for you guys.....

from what i've seen during testing for the Apogee LOA.... there are a Lot of packs on the market that can be dipped below 3v per cell within the first minute of run time when running some of the milder motors on the market, let alone the hotter ones... if you are running a cut off device that kills your system when it detects hitting 3v per cell, your race could very easily end before the one minute mark....

Tim Mohr
Apogee Lithium Batteries

[khyron]

just fyi for you guys.....

from what i've seen during testing for the Apogee LOA.... there are a Lot of packs on the market that can be dipped below 3v per cell within the first minute of run time when running some of the milder motors on the market, let alone the hotter ones... if you are running a cut off device that kills your system when it detects hitting 3v per cell, your race could very easily end before the one minute mark....

Tim Mohr
Apogee Lithium Batteries

Tim, your feedback is much appreciated. Actually I had this exact same conversation with someone from FMA when I contacted them to ask detailed questions about this device:

http://www.fmadirect.com/Detail.htm?item=2117&section=45

Their response was essentially that it is not a simple voltage cutoff, but has some more advanced/complex monitoring device that combines information about the throttle state and the current from each individual cell to decide when to warn or cut off. The specific details are "proprietary" but suffice to say they've put a good deal of thought and research into it, and it's 100% designed specifically for lipo use. I haven't found anything else like it.

(by the way there is a connector on the back, unseen in the photo, that taps into the individual cells and also a connector for an optional LED or audio alarm)

[SS Pede]

So would this lipo setup be appropriate: The little thingy mentioned above, plugged inline between receiver and ESC. Team Orion lipo. MRC 977 or other lipo charger. *no* balancer yet b/c I don't know what sort of device can balance the orion pack. Orion says the pack doesn't need to be balanced, it just affects run time.

Does that sound good? I am NOT going lipo just yet but I am feeling around... :)

EDIT: I would like to be able to balance the Orion pack if I ever get it, so if anyone figures out how you're supposed to do this, let me know. So far it's a mystery to me. :confused:

[khyron]

So would this lipo setup be appropriate: The little thingy mentioned above, plugged inline between receiver and ESC.

Stopping right there, the little thingy above won't really do anything special with the Team Orion pack because there is no way to monitor the cells inside the Team Orion pack individually. You could just as well use any other cutoff/alarm type device if you want - just pointing that out.

I can't say anything authoritative about "balancing" the Team Orion pack because I don't have one, but unless it's 2S1P (which I don't think it is) then I don't think it's really possible. It's just not electrically possible to really truly balance a 2S2P battery pack with one "tap" wire, the numbers don't add up. Someone feel free to correct me, but I can't come up with any possible scenario where that could work unless the pack really is 2S1P inside.

I'm wondering if Team Orion is just presuming for the user that partially balancing the two parallel pairs against each other will be "good enough". That's not "good enough" for me, personally, but maybe it would be for others. Maybe this is the lipo equivalent of a "sport pack" for folks who just aren't very picky about batteries - but if it is, I don't get why it costs more than lipos from anyone else with much better capacity?

[chilledoutuk]

I think your missing a trick.

There is no reason electronically you cant wire individual cells in parallel and then conect them in series.

If there are 4 cells in the orion pack then this is how I would configure them.

[khyron]

I think your missing a trick.

There is no reason electronically you cant wire individual cells in parallel and then conect them in series.

If there are 4 cells in the orion pack then this is how I would configure them.

How can you isloate each of the four cells in that setup? Balancing requires the ability to charge or discharge a single cell, any single cell. Maybe I'm up too late but I don't see it...

[tcolesen]

If you have 2 cells in parallel, you don't have to balance them individually. By their parallel connection, they will always be at the same voltage. You can treat paralleled cells as if they were one. But, you have to balance the cells in a series connection.

[khyron]

If you have 2 cells in parallel, you don't have to balance them individually. By their parallel connection, they will always be at the same voltage. You can treat paralleled cells as if they were one. But, you have to balance the cells in a series connection.

Thanks - I obviously need more sleep (or to do that 4th grade experiment with the lantern battery and the light bulb again). :rolleyes:

[SS Pede]

Stopping right there, the little thingy above won't really do anything special with the Team Orion pack because there is no way to monitor the cells inside the Team Orion pack individually. You could just as well use any other cutoff/alarm type device if you want - just pointing that out.
Yeah, good point. I just like that little thingy cause it seems like it would be small and out of the way.

chilledoutuk - are you saying the Orion pack could be properly balanced if they proper device was created? In any case, I wonder why Orion hasn't addressed this issue. I like the pack b/c it appears to be designed with more durable cells and/or case than most other Lipos. But if it can't be balanced it is less appealing.

It seems like most balancers plug into the pack while it's charging, right? It would be cool to have a more passive device that just discharges whatever cell has higher voltage to the same level as the other(s). But if the pack was already as low as it should go, you might not want to discharge it any farther at all.

[khyron]

It seems like most balancers plug into the pack while it's charging, right? It would be cool to have a more passive device that just discharges whatever cell has higher voltage to the same level as the other(s). But if the pack was already as low as it should go, you might not want to discharge it any farther at all.

No actually most balancers I've seen, including the Hyperion LBA6, can be used during charging or connected directly to the pack on their own. So the "cool" device you decribe is already available. :)

[chilledoutuk]

i dont know if anyone has taken apart the orion lipos but if they have used 4 cells then i would think that you would have to be a complete div to wire them up any other way as this way you only have to worry about balancing the two virtual cells created by parralleing the lipo cells singularly first.

[havy]

The Orion pack has a balancing port in the bottom. A little circular hole, like an earphone jack on an I pod. I don't know how the connection to the port works but we will prob see as soon as they come out with it.

havy

[tcolesen]

It seems like most balancers plug into the pack while it's charging, right? It would be cool to have a more passive device that just discharges whatever cell has higher voltage to the same level as the other(s). But if the pack was already as low as it should go, you might not want to discharge it any farther at all.

There isn't really any need to do balancing any other time than during charging. Balancing is completely ineffective below about 3.8v/cell since cells could go back into balance after ~3.8v/cell. This is caused by the differences in capacity of the individual cells, and most cells (unless overdischarged) should still be in decent balance after a discharge.

[SS Pede]

Thanks for the input guys. The Hyperion LBA6 balancer seems cool. Also, the Maxamps 6000 mAh or 8000 mAh packs are neat because they are less expensive than the Orion pack but have more capacity, plus you can request the proper tap that fits with the LBA6. Any thoughts on the durability (crash-wise or chemically) of these packs vs. the Orion? By the looks of them they should be able to handle a SS5800-powered Stampede just fine as far as amp draw goes, but I know Orion put some effort into making their pack sturdy. I just don't want anything to be damaged if I tag a tree at 30 mph or something.... :)

Thanks again for answering my questions. Maybe an MRC 977, LBA6, FMA LVC thingy, and Maxamps Lipo are in my future. We shall see. In any case, you've been great. :)

[tcolesen]

There shouldn't be any durability issues with shrink-wrapped packs unless they are ejected from the vehicle, the chassis/battery holders break, or the packs are dropped. In other words, the packs are fine unless outside forces act on them. Even still, the standard Lipo packs are strong enough, mine have been through a lot:

-Huge BMX jump caused my Rustler to land upside down on the body, breaking the battery straps that I was using.
-Battery pack came out of my 1/8 buggy after the battery strap broke, and was dragged on the ground for a bit.

[nicholcgn]

There should be no major issues with the packs. I have a 4400 set of packs I am using from polyquest with a 5.5 and you bairly feel anything after a run. I just got a set of the 8000 from max amps and ran them. If nothing changes they are great batteries for the price. I am thinking about a set of 6000. May just stay with 8's.

[khyron]

Hey I have a related question, I've been planning to get a 6000mah or 8000mah pack from MaxAmps and I've noticed that they rate their packs for lower amp pulls than Team Orion does. I've been wondering if it could be possible that the Team Orion packs, even at a lower capacity in terms of runtime, can actually handle more "pull" than MaxAmps and others? Anyone think there's any real concern there, or are they all likely reselling the same cells and some are just more conservative and others are more audacious with their safety estimates?

I've been sort of "concerned" because I plan to run a Velociti 4.5 on a GTB in my car, and I know that can pull some amps (though I don't know how many). However when I asked Novak, Charlie said I was worrying too much. So maybe I'm just a worrywart!

Any thoughts appreciated. I'm a stock racer and totally new to the idea of ever really creating a "serious" current draw since my motors were always so wimpy before...

[SS Pede]

I would be interested in knowing the answers to those questions too. I noticed that, according to Maxamps, the 2s 8000 mAh pack will not fit in a standard battery tray. Bummer. However...the stated dimensions of that pack are almost identical to my GP3300 stick packs. Just a few millimeters thicker. Also just a couple millimeters thicker than the 6000 mAh pack. I bet I could shoehorn that 8000 mAh pack into my Stampede if I tried... :)

[khyron]

I would be interested in knowing the answers to those questions too. I noticed that, according to Maxamps, the 2s 8000 mAh pack will not fit in a standard battery tray. Bummer. However...the stated dimensions of that pack are almost identical to my GP3300 stick packs. Just a few millimeters thicker. Also just a couple millimeters thicker than the 6000 mAh pack. I bet I could shoehorn that 8000 mAh pack into my Stampede if I tried... :)

As far as the sizes go, yeah, look at the exact measurements and look at your vehicle. The words "standard" and "battery tray" really don't go together in R/C, as when you get down to specifics no two vehciles are really the same.

Usually what they're talking about is "height" (defined while the pack is laying down in the vehicle). In some vehicles (say, an X-RAY T2) where the car's design "expects" for something to be able to fit over the top of the batteries this can be an issue and require moving batteries or modifying the car (in the T2 for example even a Team Orion pack won't fit because the car is designed to have cylidrical cells). However in other cases (say in a TC4) all you need is tape or a strap to use a "taller" battery because the only thing that doesn't fit on is the battery brace.

[tcolesen]

Hey I have a related question, I've been planning to get a 6000mah or 8000mah pack from MaxAmps and I've noticed that they rate their packs for lower amp pulls than Team Orion does. I've been wondering if it could be possible that the Team Orion packs, even at a lower capacity in terms of runtime, can actually handle more "pull" than MaxAmps and others? Anyone think there's any real concern there, or are they all likely reselling the same cells and some are just more conservative and others are more audacious with their safety estimates?

I've been sort of "concerned" because I plan to run a Velociti 4.5 on a GTB in my car, and I know that can pull some amps (though I don't know how many). However when I asked Novak, Charlie said I was worrying too much. So maybe I'm just a worrywart!

Any thoughts appreciated. I'm a stock racer and totally new to the idea of ever really creating a "serious" current draw since my motors were always so wimpy before...

This is what makes Lipos so hard to understand. Packs have different "C" ratings which correspond to the amp draw that the manufacturer rates the cells as being capable of handling.

The "C" rate can determine the amp draw that a pack can handle. If you have a 20C 3000mah pack, it is rated at being able to handle 60amps continuous. A 8000mah 10C can do 80amps continuous. To figure it out, take the pack's capacity in amp-hours (Ah) and multiply that number by the "C" rating of the pack.

In RC cars, the average amp draw may only be in the 20s (in the upper end for the 4.5), but the motor will be capable of drawing huge 100amp+ peaks. I'd estimate that with the 4.5 motor a pack that can handle about 60amps continuously should work alright. Of course, a pack that can handle more amps wouldn't hurt anything, but that's why there are many choices.

The Team Orion pack is rated at 20C. 20C x 4.8Ah = 96amps. The Maxamps pack - 10C x 6Ah = 60amps. Maxamps 8000mah - 12C x 8Ah = 96amps. For cars, these numbers don't really have much significance except for determining if the pack might be capable of high peak amp draws.

[khyron]

The Team Orion pack is rated at 20C. 20C x 4.8Ah = 96amps. The Maxamps pack - 10C x 6Ah = 60amps. Maxamps 8000mah - 12C x 8Ah = 96amps. For cars, these numbers don't really have much significance except for determining if the pack might be capable of high peak amp draws.

Thanks, actually that's not confusing at all - I just hadn't thought about C rating in terms of discharge! I'd only been thinking of it in terms of charge, as in charging at 1C. Now 10C and 20C rated cells make more sense to me. It's amusing that the 4800mah Team Orion pack and the 8000mah MaxAmps packs are so similar in amperage characteristics (at least in so far as they're rated by their respective resellers) because they also happen to share the same price!

[tcolesen]

Personally, I'd go for the one with more capacity. Not only will runtimes be longer, but charge times will also be shorter overall because you won't need to charge as much.

[SpEEdyBL]

Actually, the orion 4800 is only rated for 15c or 72 amps. So the Max Amps 8000 is actually better than you think.

[khyron]

Actually, the orion 4800 is only rated for 15c or 72 amps. So the Max Amps 8000 is actually better than you think.

Dude.

Sweet.

("shibby" even)

[SS Pede]

It says higher up in this thread that the Orion pack is rated at 20C (96 amps). In any case, it does sound like the Maxamps packs are fine for less-than-insane setups.

[cart213]

I'm considering the purchase of a Himodel 4S1P 4000mah pack with a 15C rating for $110. It'll go in my MT2 with the 9L and my pede with the 12s. Anybody have this pack or have any thoughts on it?

http://www.himodel.com/en/rc_hobby/electric_1292.php

I'm also thinking about a 4S1P 4000mah pack with a 10C rating from TrueRC.com. I'm tempted by it's $70 price tag but concerned with it's 40A cont./60A max. rating. It should be ok for my 12S, but the 9L might be too much for it.

[tcolesen]

Why not go with a 4s2p 8000mah pack from True RC? It's only $135.

[chilledoutuk]

I have the 3s version of the cell you mention running a 540 8s via hacker masster b comp controller and its performing very nicely and even though its overgeared in my academy sb the pack is holding up nicely only only just getting slightly warm to touch.

himodel were very quick delivering my battery as well via dhl.

[tcolesen]

chilledoutuk, unless you bought the pack within the past month, then you have the older cells that were rated at 4C/6C continuous. The new ones are 10C, and provide much better performance.

[chilledoutuk]

i bought these this week they specify 15 continuous i would not get anything with a lower c rating.
They sell some 2200mah 20c cells as well which i was interested in getting 2 packs and paralleling.

I decided the 4000mah pack was enough and keeps it simple and compact.

[cart213]

tcoleson, that 8000mah pack is also on my consideration list. But I honestly don't think I need that much capacity. I rarely run for more than 30 minutes at a time, and my 12s lasts 25 minutes with my IB3800 cells. Plus, that pack weighs 9 ounces more than the 4000mah pack. I was hoping to get a weight savings by switching to lipo.

What's more important to me, weight savings or increased capacity? Decisions, decisions.

I'm also considering the Emoli cells, but a 4S2P pack wouldn't fit too easily in the pede, and a 4S1P pack probably wouldn't have a high enough C rating. Those cells are good for about 40 amps cont., right?

[chilledoutuk]

cart remember that reducing the weight of your vehicle will also increase runtime.

On the other hand having a battery capapble of a higher discharge rate means it will perform closer to its rated mah performance when having current pulled from it.

My advice is take into consideration where the battery pack will reside and how the handling will be affected by halfing the weight of your battery pack.

I have a schumacher axis 2 which has a saddle pack configuration with the cells right at the back of the car i put each of my paralleled kokam packs on either side kinda sadle pack configuration.
It wasnt until I took it out onto the open road that i realised that most of the backend weight on that car is generated by the cells.
Halfing this weight made the backend very light and the car oversteered like mad.

the same happended with my academy sb as the pack was much lighter the balance of the car was upset and the car torque steered so bad it drove me crazy.

Now I have a 3s 4000 mah lipo in the academy sb the extra 100 grams or so has created a good balance on the car and now it does not torque quite as bad as it did with a lighter pack.

in a car that has the pack placed centrally such as 2wd buggys and trucks and even the dark impact you could go as light as you can with high voltage and get yourself a low kv motor to go.

[botmund]

Back to the safety issues, what are people doing? My intent is to become informed, but understand the practical use.

1. Are you charging and storing in fire safe containers? What do you use?
2. Are you always around for charging?

Ok I'm bumping an old thread now... :p

1. I ALWAYS charge in a "fire safe" container. Very easy I bought 2 pots, 1 Leca block and 1 square concrete slab (45cmx45cm).
Slab underneath, Leca on top of that. Inside the hole of the Leca I placed the smaller pot (upright). On top of that pot goes the larger pot(upside down). That is the larger pot covers the smaller. LiPos goes in the small pot when charging. There is a void beneath the smaller pot and the concrete slab. Also both pots have a hole in the bottom. If something were to happen the excess pressure can escape both up and down. Gas escaping downwards escapes between the small pot & Leca block. Gas going upwards goes trough the hole in the large pot and also between the two pots.
Sorry, I don't have pics of this arrangement. Total cost was perhaps 10euros.

2. I am not in the immediate vicinity, although I never leave home when charging.

I have never had any serious incidents with LiPos. I have crashed badly with my 1/18th car (many times) and my brushless plane (Slow Stick) (about 5 times B A D that is) and never have the LiPos gone bad. I consider LiPos safe as long as you follow the guidelines.

[tucsonbroker]

I did go the LiPo route and bought a $40 firesafe from costco. I charge and store the batteries in there and only charge when I am home. Thanks all for the advice. LiPo batteries give an AMAZING punch.

[RobK]

I just bought my first set of lipo batteries a couple of weeks ago--2 Maxamps 8000mah 2s2p for my HV-Maxx brushless Revo. The new batteries gave a pretty impressive gain over 12 good NIMH cells, as much has the HVMAXX over the stock EMAXX titans I was using. I am so impressed with the runtime, weight per mah, and delivered voltage that I'm never going back to NIMH--worth every penny.

I charge my lipos with a ICE charger in a pyrex pot w/lid, although I'll probably get a proper fireproof container this weekend.

[smeghead]

Hey anyone had any problems with intermittent power on full throttle ,I only gets it with me 5000mah lipo's when running me 4200nimhs no problems at all so i am illiminating motor / speedo problems .
The motor is a Novak ss5800 set up the problem is only on applying flat out throttle like i aint scared to .
Any help would be apprieciated