C50 + Master Comp + Li saver and what Lipo pack?

[standard_63]

I'm looking to convert my Emaxx over to Lipos for the lighter weight, and I'm wondering which Lipos I could use for the C50 motor with the Hacker Master Comp ESC and a Li-saver and Kool BEC. I curently have Kokam 1500 3S packs 10c, but am thinking I will need higher discharge packs? Or can I get away with these ones? I realize they won't be 14.4v, but I think they should still work ok? I want to use a single pack rather than two packs if I can. This conversion should save a ton o' weight in the Maxx!!

I'd also like to use the lipos in my xxx-4 with a 5300basic motor, and an older shulze esc, was out before the 14.97 I think?

Anyways, I'm still learning about these batteries, so any help will be appreciated! Thanks!
--Jonathan

[pinolelst]

You'll need higher capacity packs for certain unless you have 4 of them or more to run in parrallel.1500 mah pack at 10C is only a 15 amp limit,I suspect you'll be pulling 50 amps or better in a truck as big as the emaxx

[tcolesen]

The peaks for that motor could probably run up to 100 amps, especially on a lower voltage then it is rated for. I would say that you would want at least a 60amp continuous rating for a Maxx. Then you would want 14.8v for that motor. So if you were to use 3.7v 2500mah cells with a 12c continuous discharge rating, you would want a pack with the configuration 4s2p. That would probably cost $150-200. But it is better than over-discharging a LiPo battery that could lead to the battery exploding or something else like that.

[glassdoctor]

For an emaxx you have to keep in mind that the batteries need to be two separate packs to fit the chassis ideally.

Do you want 3s or 4s packs?

For 3s, you could go with two smaller capacity packs... one in each battery tray, wired in parallel to double capacity. Two Polyquest 3s 2600 packs would be very good. This pair would be 5200mah, rated for over 60 amps continuous, and would weigh only 15 oz!!! (one 6 cell GP3300 pack with deans wiring weighs 14 oz) :)

It seems unreal every time I add up the specs of good lipos..... :)


4s lipos give some more options... you could put a 4s pack of choice in each battery slot, like I mentioned with the 3s.

Or you could put a 2s on each side and wire them in series, just like 6 cell nimh packs, with the bonus that the 2s lipo packs could be easily used in 1/10 cars too. If you do that just make sure both packs get equal usage...

[standard_63]

I was thinking that since the motor is on the right I could put the single pack on the left, and since it's so much lighter than the regular battery it would more or less be balanced ok. I could also put the ESC on the right side as there would be more room for it over there.
I also like the single battery idea for wiring up the li-saver and the super bec. If I keep the dual battery and dual plug on the Hacker Comp, could I still wire the li-saver to just one side and have it monitor both batteries? And the super BEC should be able to wire in there too, right? One off each plug? Super BEC on one plug, and the li-saver on the other?

[standard_63]

or, single connector to ESC, and these:

2 of these...

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHFG1&P=M

and one these...

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHPN2&P=7

This would be pretty close to the 6cell GP3000s I run now, right?

[glassdoctor]

Well, if you want a real simple setup, and just a single pack on one side of the truck you don't need to buy 2 packs and mess with that.

Just get something like a single 3s pack of 3000mah+ that fits in the satock battery tray. Emaxx stock chassis tray is 47mm wide. If you dremel it out a little wider.. to @49 mm then I would go with a single Polyquest 3500-4400 pack ( they are listed as 48mm wide)

For a really light battery that would fit easy, look at the 45mm wide PQ packs... 3100, 2600, 2200... they are rated 12C+ so even these small packs should do well unless you are really hard on them like running in tall grass, etc. They're cheaper too... :)

www.maxamps.com has some good lipo cells I'm going to get for my 1/8 buggy. They will make up a custom pack however you want. They could make a 11.1V 3300mah pack for under $100 that would fit a stock emaxx tray... and it would be very light, about equal to a 4 cell nimh pack. Wow, I guess that would help make an emaxx scoot pretty good!

[glassdoctor]

The BEC and lisaver wiring should be pretty simple. Just connect them to the controller's input wires, like right at the esc's battery connector plug. Solder the leads for these accessories along with the main esc wires.

[standard_63]

Cool, thanks!! That's what I thought for the wiring, glad to know I won't melt down--seems simpler with one battery. The PQ 3100 should be pretty good, I think that's what I'm gonna try. :)

[Reinhard]

for E-Maxx:

Kokam 3s1p or 4s1p 3200HD

4s1p:
weight: 340g (less than a 6cell-Nicd-Pack !)
continousl-current: 50A, with cooling 65A
peaks: 80A for 5sec should be ok.. maybe 100A for <1Sec

for Losi XXX-4:
i run 3s2p 4200mAh on a 3000kv-motor...
optimal in my eyes would be:
a motor with 2500-2700rpm/volt
and 3s2p or 3s3p...
with that setup a cheap 40A or 60a controller will be enough..

[standard_63]

I ended up with a maxamps 3100 4s pack, lisaver and UBEC. My Emaxx rocks now like I never thought it would! I lost over 2 lbs. from the truck losing the 2 6cell 3300 packs and the reciever pack, and now I have the Emaxx I've always wanted! :) Way less abuse going on with the lighter weight, and it takes off like a scalded cat. I think the Master Comp controller is even working better than ever not having to work as hard. Motor heats up a bit, controller is slightly above warm, and the batteries just get warm. God bless lipo batteries! (at least mine so I don't ever have a fire, knock on wood)
--JD

[Mr. Constructor]

wich tech datas has the lipo safe that connects between the pack and the esc, these are REALLY important datas !!
the safety of your electrics AND other persons will be influenced by this, as i know there is NO good safety electric out there, so the use with a esc that is not lipo cut off selectable will be a not that good idea.

But if you wanna look at some good kokams:
check out the 3200mAh ones they could hold up to 60A (was tested by a flight freak in germany with a very good reputation) !!

OK they´re not that cheap, but the best so far alternative !!
(then you could use 2x 7,4 V packs, wich is ideal for a Maxx replacement)

[standard_63]

The Li-saver seemed to work ok, but I can't find any specs.

This is what I got:

http://www.newcreations-rc.com/ProductDetails.aspx?itemnumber=Lisaver

Think it's no good?

Which ESC for EMaxx that has Lipo cutoff? For use with a C50 Maxx motor or XL type. Preferably with BEC if possible.
Thanks!

[DaFF]

Do you guys think at using this thing for esc that doesn't have a lipo low voltage cut-off mode ?

Because if that is so, thern forget about it, it will melt before you even push start your car... I remember someone saying it is only good for little plane with setup that draws only a few Amp ( less than 10 anyway ).

Watch the size of the wire, even with 10 Amp, they will get roasted !

DFF

[Reinhard]

would be interesting to know how it works..

just read some minutes ago, that the lipo-controllers work that way:

when the batt reaches a certain value under the start-value (volt) they turn off..

so:
startvalue: 4,2volt
when the volt reach 71% of that (3Volt) the controller turns off...

BUT:
when you use a only halfe-full charged batt or you have already used the batt and connect it again, the
startvalue may be 3,8Volt
now 71% are only
2,7Volt

so: when you connect a nearly empty batt, the controller will turn off very late, maybe the batt will get damaged... !!!
didn´t know that...
thought the controller estimates from the voltage it measures that it is a "3S-pack" and knows: 3S = 3*3,0Volt = 9Volt, then turn off...

at least the schulze-controller work with the %-values...
so: how does that little extern-lipo-cutoff work ?

[glassdoctor]

I believe the li-saver works reguardless of the size of model, current, etc. because the current doesn't flow through it, only the rx signals.

The li-saver does not cut off the motor, but it pulses to let you know it's time to "land". If you keep "flying", it pulses harder until it finally cuts off power.


As for the voltage cutoff point, I think it "detects" 2s, 3s, 4s, etc... when you plug un the battery... and sets the cutoff accordingly. It's possible you could fool it by plugging in an almost-dead battery... so a 4s might be detected as a 3s.


Thats the way I understand from reading the rcgroups.com forum

[Mr. Constructor]

glassdoctor is right, this little tool will only detect a voltage down in the system then force the esc to pulse around.
the only thing i will not feel good with:
at wich voltage will it do that, it´s not said, and a whats about a failure, will it "control" the esc then with bad signals or will it only not send the "end beep" ??
sorry, but for such high cost systems, it is much better to have this cut off inside the esc, but this thing seems to work either.
But if ya wanna like the best truck esc: mgm 120A 12 cell with 1,5 A BEC (within the full cell range) and only around 185 Euro each.
I use this one in my new 8th, really a great esc (watch the review thread in this forum)

any schulze 18.97 or anything like that will be ok either but at a much higher cost !!

[Reinhard]

hmm..
i have 3 brushed-controllers, and 5 brushless-controllers without Lipo-mode..
only one with lipo-mode..

so: i can´t afford to change 8 controllers to lipo-controlllers..
for me this extern-lipo-safe would be great if it works right..
i would only need one, and can swap it within seconds from model to model....

only in heli it would be useless with governormode...
but there i can calculate the flying-time much easier by clock than on a rc-car...

[standard_63]

It seems to work, I plugged in my 4s pack thinking it was charged, and the the truck just lurched forward, stopped, lurched a tiny bit, stopped, and then I realized the pack wasn't charged. It was about 3.8v when I hooked it up to the charger. It came with no explanation on how it works except that it's good for 2-12 cells,but it seems fine with the 4s lipos, no meltdown yet--it doesn't even get warm, and I have way less glitching for some reason with this setup vs. my old nimhs, including receiver pack.

[darkultra]

standard_63,

Exactly what pack did you get, did maxamps build or was it a Polyquest 4s Pack?

What current limit is your Hacker Comp ESC set at? I belive they come at 30Amps defalt setting.

Have you stock drive-traing? When the car is so light we won't need metal CVDs, right?


I have nearly same setup and wanto go LiPo too

[Reinhard]

don´t wast mone on Polyqest !

they are overrated in
capacity
and in C-rating..

and they loose capacity very fast..