Do i have this rite, mmm 2200 and lipo choice

[twisted8]

from what i understand you want a lipo pack that will supply what the motor draws at peak current.

the castle 2200 draws 120 amps at peak so i want atleast a 5000 28c lipo ?
5000x 28c = 140 amps...

am i on the rite track ?

thanks!

[fastbaja5b]

depends if ur goin 4s or 6s, your gearing, what kind of rc it's in etc etc

25c packs would be fine, your constant amp draw wont be anywhere near 120 amps it will be about half that. Gear for 40-45 mph and you will be good to go

[twisted8]

fastbaja5b,ill be running this set up in an emaxx on 4c

azjc, i dont understand how gearing for a speed will help ya. there is so many variables. i understand how the calculator can help when trying to figure out speeds but rite now iam more worried about over heating and getting the rite lipos.

[Sammus]

120a rating doesn't mean the motor peaks at 120a, it's a rating of what it can handle. you could make the motor draw a hell of a lot more than that if you tried :p

Also, gearing for a particular speed in a known truck tends to indicate the power requirements will be pretty similar, so a lot of people here gear for a particular speed.

[lincpimp]

An emaxx on 4s needs a batt capable of at least 125amps cont, I would go for something with 150amps cont myself. 4s is hard on lipos, you really need 5000 30c lipos, or 6000 25c. A pair of 3000-3500 30c 4s packs wired in parallel would be my choice for the emaxx, as I do not like packs made with internally paralleled cells, such as the larger mah maxamps packs. Some enerland 3200 30c 4s packs would be a good combo. Or maybe a pair of zippy 4000-5000 20-25c 4s packs wired in parallel. Not as light as the 30c packs, but much cheaper. Still close to 200 bucks worth of lipos.

The previous info was given assuming that you will gear for 40-45mph. Higher gearing will require better lipos if you plan to continue with 4s. If you want speed go to 6s and get a pair of 4500 30c 3s lipos, or go all out with 6000 25c 3s lipos...

[Sammus]

linc: why dont you like internally paralleled cells? I always imagined them to be better...

[lincpimp]

Originally Posted by Sammus

linc: why dont you like internally paralleled cells? I always imagined them to be better...

Actually I have really thought about this, and can find no benefit at all with internally paralleled cells. Unless they are matched perfectly at the factory, you always end up with one strong cell attached to a slightly weaker cell. When you approach the pack limits the weak cell can't keep up, and often the weak cells puffs, or the strong cell handles the load, but it will decrease that cells life cycle. Plus the strong cells will hold voltage better, and packs with internally paralleled cells will require some cool down time to eqaulize voltage between the pairs.

Now if you have a pair of packs you can run them in parallel and then charge them in series. That way you can balalnce all of the cells during the charge, and not pairs of them... You will need a charger/balancer combo that can handle that many cells in series, which does get expensive. But you can charge the packs seperately, and as long as they take a full charge they will be quite close in balance.

You will also notice that most of the "better" lipo producers do not make packs that have internally paralleled cells. Flightpower will make paralleled packs, and their cell matching is 2nd to none... Maxamps have a few internally paralleled packs (8000, 6000, etc) and I have seen many of those fail, mainly due to poor QC and matching...

[Sammus]

I always thought the 'weaker' cell is weaker due to a higher internal resistance. Thus being paralleled with the stronger, lower resistance cell, the load would be distributed proportionally (ie stronger cell loaded up more). Otherwise the weak cell would be under as much load as the other, presumably stronger cells, in its battery.

I guess in the end if you have a weak cell, you have a weak cell. It's going to be stressed no matter how it's connected, best have it die young by itself in its own pack, rather than give an unfair load on one of the good cells and make it fail early...

[lincpimp]

Originally Posted by Sammus

I always thought the 'weaker' cell is weaker due to a higher internal resistance. Thus being paralleled with the stronger, lower resistance cell, the load would be distributed proportionally (ie stronger cell loaded up more). Otherwise the weak cell would be under as much load as the other, presumably stronger cells, in its battery.

I guess in the end if you have a weak cell, you have a weak cell. It's going to be stressed no matter how it's connected, best have it die young by itself in its own pack, rather than give an unfair load on one of the good cells and make it fail early...

Yeah, weak is weak. Maxamps do not match their cells, so that is why the paralleled (and other) packs have issues.

I just really prefer to parallel the cells outside of the pack. Makes it easier to keep tabs on all of the cells, and catch problems before they cause issues...

[twisted8]

just when i thought i was starting to understand this all.... lol

well earlier today i bought two smc 28c 5000 mah packs. i put an 18 pinion on with the stock 68 gear and will go from there i guess.do some runs and check the temps.

[lincpimp]

Originally Posted by twisted8

just when i thought i was starting to understand this all.... lol

well earlier today i bought two smc 28c 5000 mah packs. i put an 18 pinion on with the stock 68 gear and will go from there i guess.do some runs and check the temps.

Sounds like a good way to approach it. Should be fine, that is CC speced gearing that comes with the MMM combo.

[Sammus]

Originally Posted by lincpimp

Makes it easier to keep tabs on all of the cells, and catch problems before they cause issues...

Now there's some good reasoning. I wont be paralleling cells inside any parallel packs I make in the future

[lincpimp]

Originally Posted by Sammus

Now there's some good reasoning. I wont be paralleling cells inside any parallel packs I make in the future

I will also add that making parallel cell packs is a pain in the ass. I much prefer to make a parallel adapter with some deans plugs and spare wire...

Plus you can always use the packs as series or parallel. I did this with 4s packs i had, series in my bombproof emaxx with the 1100kv aveox, and parallel with the 1515 1.5d in the erevo. Just had to make adapters for each...

[Sammus]

Originally Posted by lincpimp

I will also add that making parallel cell packs is a pain in the ass. I much prefer to make a parallel adapter with some deans plugs and spare wire...

Plus you can always use the packs as series or parallel. I did this with 4s packs i had, series in my bombproof emaxx with the 1100kv aveox, and parallel with the 1515 1.5d in the erevo. Just had to make adapters for each...

Yeah I running your packs in different configs only becomes a reality when you have like a billion different RCs though maybe one day I will too :p