Brushless/Lipoly 12l3 @8.4 volts!

[lonepalm4]

!!!Here are some pics of my 12l3 w/ the novak brushless system and the new Kokam 15c super high discharge packs. I just got done running the car, and all I can say is Holy !!! I've been driving rc cars for nealy 10 years and this car has the most absurd power to weight ratio I have ever driven! It's silly fast at 1/4 throttle, too fast at 1/2 throttle, and waaay to powerful and fast at full. Hit 1/2 throttle and nail the trigger, and the car smokes the diff and tires and spins wildly down the street at 40 mph. Sweeeet! My first run lasted over twelve minutes, and the combined pack still had over 1000 mah left. Granted, I was very easy on the trigger to avoid spinning the car constantly, and was running on low traction surface, but I was still impressed with the runtime with so much crazy power/speed.
I haven't weighed the 2000 mah packs yet but together, they feel slightly heavier then a 3300 4 cell pack, but lighter then a six cell pack, and I think the novak system is slightly heavier then a brushed setup. I am using 2 Kokam 2000mah packs in parallel that will give a 60 amp continuous discharge at 8.4 volts and 4000 mah. I figure the car will pull close to 30 amps continuous and nearly 60 peak under high traction asphalt conditions. I had to mod the car a bit to get the ss speedo under the shock, but it seems to work ok.
Anyway, I'll do more testing on the longetivity of the packs through multiple discharges and runs and keep everyone posted. The setup looks kinda hack right now, as I just wanted to get the car on the road and see what she could do. I can't wait to smoke the gas cars on the back straight!!!! My eyes have been opened!!! Go brushless, or go home. *As always, be careful with lithium polymer batteries.
Till next time..........

[BCSavage]

those lipo's are intriguing yet scary as he||. I heard they can blow up radnomly, are a pain to charge, all kinds of horror stories. "Definately not for the faint of heart" is what I read somewhere and "no amateur show even THINK of these in their setup"

So as a user, you should enlighten us with charging techniques and such. :D

[Skribble]

Blow up randomly? Have you heard of laptops ever blowing up?

If you follow instructions and use the right equipment, I wouldn't see why there would be any problems.

By the way .. insane setup. Better keep downs batteries buckled down!! Or they would go for a ride of a lifetime.

[BCSavage]

no, these are just things I've been reading on the net. Could've been peoples mistakes but I'd rather know everything about them before hand. Plus aren't they pretty expensive right now?

[lonepalm4]

Anything can be dangerous if misused or abused. With that said, I am taking every precaution in protecting myself and property. I use the astro flight lipoly charger at 1c charge rate (never exceed this with any lipolys, and always use a lipoly specific charger) and never leave the batteries unattended. If the batteries fail (due to damage or overcharging), they will first swell giving you time to dispose of them before they ignite. I was charging them inside my ceramic crock pot, but I think this is overkill if you are watching them frequently. Also, never charge a damaged cell. I have heard that many failures are traced back to neglect in the discharge cycle due to massive current draws. this is why i sprung for the 15c kokam packs. if the manufacturer says they are good for this amount of current, i believe them. I question some of these people who say these packs rated at 3c can be used in high amp draw applications like rc. If they are rated at 3c, and you are pushing them to 10-15c constantly, I have little sympathy for the backyard rc'er who lights all his stuff on fire. Bottom line- if you want to use lipoly's, it is better to overestimate the current draw you think your car will pull and build you setup with plenty of room for error, or accept the results. I am still a little scared of these packs, but as with other people who have been in the hobbby for a long time, I remember when nicd packs would smoke and light on fire due to overcharging and discharging or neglect. i think the massive stides in lipoly cells of late will continue, making them the next power source for rc. the nimh packs have been out for over 7 years and have only increased capacity from 3000 to 3600 mah (less then 20%) increase, and they will always be heavy in comparison to lipoly technology. Lipoly's have only begun to be used in high amp situations, and they have increased from 3c to 20c (kokam) in a few years. This is great progress, and they should have plenty more room for advancement. It's a great time to be in rc!!

[bomb-proof]

I have used and misused mine, never a pain to charge, and hold a full charge for weeks at a time. I have had them come loose and bounce around, with no nuclear explosions or poison mustard gas being shot out into people's eyes like I would expect after reading all the horror stories. Maybe thats about like one of the major motor companies telling us brushless motors are really not as good as brushed.......

[BCSavage]

lmao BP, you made me giggle with that one.

So lone palm, all in all, what kind of investment is this? and is brushless the only esc/motor setup that will take the juice?

[DaFF]

Lonepalm4, way to go ! I like your car !

I know what is the feeling of a BL & Lipo. I know it will slowly but surely make his way into our r/c car.

There is no question to me that Lipo are better than NimH.

I'm still working on 1/10 sedan BL + Lipo project and I know I am pretty close to tackle this project down in order to have an extremly fast, extremly light and nimble car.

Anyway, be carefull on the way you have your pack attached to your chassis. My personnal experience is that I won't put anymore tape close to the battery tab. If I where you, I would only put double side tape on the bottom of the pack and a safety strap tape like you did along the widht i.e. if I where you, I would remove the piece of tape you've put on the lenght on the batt in order to avoid any stress on the batt tabs.

Furthermore, you might want to protect the exposed batt corner with some foam. From past experience, any little nick on the corner and your batt will be puffed.

DFF

[Skribble]

I have had them come loose and bounce around, with no nuclear explosions or poison mustard gas being shot out into people's eyes like I would expect after reading all the horror stories. brushed.......http://img.photobucket.com/albums/v65/pro-LINE/RolfCopter.gif

[BCSavage]

http://img.photobucket.com/albums/v65/pro-LINE/RolfCopter.gif

uhhhh... ? :confused:

[Skribble]

uhhhh... ? :confused:RCZ doesn't allow .gif's to be [IMG]. I just found bomb-proof's quote to be funny.

[BCSavage]

Ahhh, K now I get it. HA! lol

[BCSavage]

So is this the right kind of battery to use? Can it be used with any ESC that'll handle the voltage or does it have to be a special controller (ie: brushless)? Will a Novak brushless system take it?

[lonepalm4]

Hello again. Well, I just took this project a step further by ordering the on-board data acuisition program from eagletree. I also sprung for the electric package that will allow me to continuously monitor battery voltage and current. With this, I will be able to post real scientific results of battery performance and degregation throughout the life cycle. It will also allow me to monitor motor temps, sc temps, speed + motor rpm (by calculating roll-out and knowing the rpm of the spur- with the included rpm sensor). I will now be able to download the data to my computer after a thourough work out and know exactly what happened durring the run to the batterys + graph the results. Pretty high-tech. Mostly, this will let me know the peak current that is being used and try to correllate this with battery degragation as opposed to continuous amp draw like the battery manufacturers do. Hopefully, these cells last long enough to get good data (and a few killer runs). I have heard that the peak amp draw is what hurts these batterys the most. I will try to post the results as soon as i get some good data. Also, does anyone know if a resistor or such can be hooked inline with a hall sensor to increase it's range of measurement? the unit will measure up to 90 amps which should be plenty for this project, but it would be nice to be able to measuer higher currents for future projects. Also, just to clear up, lipolys can be used with any motor/sc package that will handle the voltage and current, although brushed motors tend to draw more current vs brushless for the same performance. Keep the fire burning......

[starluckrc]

Not sure how they come up with the 90 amp limit. Perhaps it's an accuracy issue of that. Mine logs spikes over 120 amps regularly.

[DaFF]

I also plan on ordering the Eagle Tree system.

Starluck, how does it work for you ?

Do you found it a valuable, precision tool or just another useless toy ?

DFF

[starluckrc]

So far I've only used it for some current figures and voltage drop measurements. The temp probe doesn't conform to an electric motor vary well, so it isn't that accurate. I could benefit from more hall effect sensors for all my speed controllers as well since it is too small to slide over my 4mm connectors. It's neat to see what's going on when you drive but probably not practical for most people at the cost. It's pretty much a necessity for my business with the way people have been burning up contollers in the past. I'll have a lot more info once I get some controllers in for myself.

[DaFF]

OK, thks for the info !

DFF

[itdood]

Blow up randomly? Have you heard of laptops ever blowing up?

If you follow instructions and use the right equipment, I wouldn't see why there would be any problems.

By the way .. insane setup. Better keep downs batteries buckled down!! Or they would go for a ride of a lifetime.


Laptop batteries are completely different and never exposed to the charge / disharge rates that RC cars pull. If you used a laptop LION battery in an RC car, it would most certainly overheat, die, and might catch fire.

LIPOs have a big history of destroying property in the RC world, from destroying models, cars, and houses.

This house was destroyed when the guy left his house to walk his dog while he was recharging LIPOs on a Triton. The batteries were even on a ceramic plate just in case.

Before fire:

[itdood]

after

[nicholcgn]

I never remember reading that it was the Lipo's that caused this. I thought he was charging serveral differnt types of batteries? Did anyone confirm it was the lipo pack?
But this also just emphizes the point that you should never charge any battery unattended. It does not matter if it is Lipo/NICD/NIMH or whaterver other technology is out there. The key is usng the equipment correctly and following instrctions. Yes there is more of a risk with LIPO. things are changing with them all of the time. Research the equipment and understand the RISK!!!!!!

[itdood]

I never remember reading that it was the Lipo's that caused this. I thought he was charging serveral differnt types of batteries? Did anyone confirm it was the lipo pack?
But this also just emphizes the point that you should never charge any battery unattended. It does not matter if it is Lipo/NICD/NIMH or whaterver other technology is out there. The key is usng the equipment correctly and following instrctions. Yes there is more of a risk with LIPO. things are changing with them all of the time. Research the equipment and understand the RISK!!!!!!


Nothing definitive about the LIPOs but everything pointed in that direction.

I've seen video of LIPOs letting go and because it's explosive instead of merely catching fire, I think that makes them even more dangerous than any other battery. It was like a blow torch when they went. And I've seen tons of posts about them blistering for no reason at all. I wouldn't trust them. If I used them, they'd never be in my house for anything, not even charging.

Newer cell phones are coming with LIPOs, and I recently saw a story about someone who had their cell phone catch fire, on them, and the burns were severe. I don't know if it was a LIPO phone but I suspect it was. Because the burns were so severe and the amount of sudden flame, I don't know of any other battery technology that can catch fire that fast, with no warning, and that severe other than LIPO.

I wouldn't be able to sleep at night knowing they were in my house.

I've even considered getting them. If I did, they'd be kept in a fire safe, in my shed.

[lonepalm4]

here is the data from the eagle tree system. I was surprised to see that the little 1/12 scale car managed to pull over 100 amps on a couple of occasions. It looks like at full throttle, the car usually pulls 50 or so amps when reaching top speed. the super high spikes may be from when I spun the car and gassed the throttle. I'll do some more runs and post the results. The first run, I was recording too many paramaters, and the eagle tree system shut down after 6 min due to running out of memory. Next run I will only record the amps and volts of the pack. THe pack was 100 deg. F according to my raytec temp gun after the 12 min run, and the pack was nearly dumped. More data to follow.

[lonepalm4]

pack volts over 6 min run:

[DaFF]

100 deg F is OK. It seems that 150 deg F is the limit were you don't want to go and you are below that.

I'll be a little worried with the Amp spike tough.

100 Amp is a a lot for 60 Amp max lipo. You might be reducing your battery life, but I am not sure.

BTW, same goes for the low voltage. You're going way down, pass the minimum voltage recommanded per cell ( 3.0 volt per cell, 6.0 volt for a 2S pack )

For how long do you go below 6.0 volt or more than 60 Amp ??

Seeing those graphs, I would run a lower Final Delivery Ratio, just to be on the safe side, but you might want to have another ( more ! ) expert advice ...

Another thing: did you measure your pack voltage before the test ? It doesn't seems it was at 8.4 volt at the beginning... ( might not be fully charged ? )

Anyway, thanks for sharing those graphs. That's excellent info.

PS: What do you think of the Eagle Tree system ? ( thinking at getting one too )

DFF

[TheSteve]

I don't know if you're ever going to see 8.4 volts with any kind of load - a 2 cells LiPo pack is rated at 7.4 volts. You can also have a LiPo pack drop below 3 volts per cell if its under a lot of load - but I wouldn't want to see one go below 2.75 under load. Having the voltage sag that low is also a concern if the cells aren't matched really well.

I'd love to see the current spikes with my Hacker c40 6s when I punch it...

[lonepalm4]

So I was doing some fuzzy math on how fast I think this booger goes, and by using xtreme rc's 35mph benchmark for a 1/10 sedan w/the novak, I calculated that this car should hit 55 mph. (I ran the rollout on my 1/10 w/ brushless + compared that to the rollout of the 1/12). i figure this is ultra conservative. Taking into account the light weight and higher voltage, I think this car should hit 65 no problem. I might hook up the speed sensor to my xray soon just for giggles. Since I broke the axle on the 12l on the second run, I swapped the stuff (minus lipolys) to the xray and did a run w/ foams and 2400 mah batts. It was interesting to see the difference in the V+I between the two setups. Amazingly, the 1/10 did not pull more peak amps then the 1/12. Maybe this is due to the increased traction and lack of burnouts the 12l was doing. Also lower voltage. Although, it did pull more continuous amps due to the ability to actually control and drive the thing.
Daff: Yes, the battery was fully charged before the run. Also, the recorder was measuring 10 times per second, so the actual time spent in the extremes (I+V) was very short - probably under .25 sec. I realize that this will likely kill the batt sooner - this is what i am trying to measure- how quickly, and what the results will be. Also, kokam rates this pack at 60 amps continuous, I dont know exactly what they rate the peak at- never seen this posted anywhere. I think the drive ratio is about perfect, however. I like the eagle tree system, especially the electric add on that records the I + v. It is perfect for testing these lipolys. The other features are neat also, and the software is feature packed.
The Steve: As the graph shows, the lipolys average around 7.2 v under load - much lower then the 8.4 that the pack shows off the charger. Compare this to the 2400 pack data attached - still a higher average v.

[DaFF]

Lonepalm4,

Up to my source, the Kokam 2000 HD are rated at 15C peak ( for 10 seconds ) and 10-12C continuous... ( The Kokam rating is kind of confusing, as they state only 15C continuous 90%)

However, I guess it should be OK to pull more Amp for 1/25 sec !

Looking at both Lipo and NimH, we can clearly see the Lipo sustain the load better by dropping less volt than the Nimh.

Anyway, I like all the graphs you post, it's very good info, thks for taking the time to share this with us.

I'll get the eagle Tree and will post result too so that we can compare apple to apple.

I hope to have enough time to play with the UF setting and records graphs like you did to see how the UF setting affects the Amps drawn and voltage. I'll do the same with different gearing.

DFF