More C or mAh ?

[Flying Scotsman]

Agreed, especially about wild claims by some battery assemblers.

Douggie

[domwilson]

Yep. There are alot of manufacturers that post wild claims. They should post more info. about their batteries, like internal resistance and at what temp. I guess this brings us back to "What brand"?

[Tony]

Hi guys,
Thanks for the infos. First of, i meant to say 2x2s1p 7.4V in series. It seems everyone is leaning toward more C rating rather than more mAh. I had been using ThunderPower lipo 2x3s1p in series. Switching to Zippy lipos, cost alot less for sport run. So, i guess 2x2s1p 7.4v 4000mAh 25C will do for my set up?

[domwilson]

I have heard good things about the Zippy's. As always, watch the temps.

[bwells]

Dom, went to your link and one sentence in it still throws me, " by going parallel, I doubled my "C" rating". I understand the effect series and parallel have on voltage and MaH but the C rating is really hard to accept that it will double in parallel or series. The formulas used seem to be a guide line to get you close but not a perfect representation of what you will get. 2 10C in parallel gets you 20C is what I am having a hard time with!

[domwilson]

Just think "amps"

[domwilson]

Part of what determines the "C" rating of the battery is the internal resistance. By paralleling "resistance" you effectively reduce the resistance and allow more amps to flow. http://www.kpsec.freeuk.com/resistan.htm

[NativePaul]

By paralleling you do halve the resistance which allows double the amps to flow, but because you have doubled the capacity the amps available per amphour of capacity figure ("C" rating) stays just the same.

Personally I would go for C rating over capacity in most cases, it is however much easier to lie about C ratings than it is capacity as its a small minority that will ever push the rating continuously but everyone's charger has a capacity readout, so you have to be a little more wary of your suppliers.

[Jeff Wohlt]

C rating is great and we want the most we can get (big pipe vs little pipe for flow) but if you have little mah then your power curve and pack life goes to crap because you will get one minute at 100 amps. (just a sample #)

So you get a very short runtime with good power then she starts to drop off or cook.

Depends on what you need. For anything I run I want at least 25C and at least 4000 mah. I would prefer 25-30C and 5000 mah.

There are so many options for lipo. 2500 4S mah with 10C each pack and para wiring then you get a 5000 mah with 20C pack and 4S.

Best thing to do is buy the packs with the same C and mah rating so you can always configure what you want. 2S & 3S packs can give you lots of options.

Oh...and do not expect to draw big big amps if the packs still have small wire on them. 12 awg min!