Confused about classes of RC LiPo batteries


I am shopping around for a LiPo batteries for a robot. I found the classification of batteries confusing. I understand that higher mAh means they may last longer between charges, and that has a fairly clear definition in the Physics. Higher S rating means more cells (eg 3S = 3 cells, I think).

But I don't understand the 25C, 35C, 70C classification. I believe higher 'C' means greater rate of power delivery. So eg you can have greater acceleration in an RC car with battery 35C than 25C. What does C stand for? What is lacking is a scientific explanation, maybe a relationship between 'C' value and watts per sec ? or a quantity such a peak power (watts), or peak current with a time limit (like you get for some electronic components).

Anyone able to point me in the right direction on a tutorial / website / explain.

Many Thanks

A battery with a discharge rating of 10C would mean you could safely discharge it at a rate 10 times more than the capacity of the pack, a 15C pack = 15 times more, a 20C pack = 20 times more, and so on.

Let's use our 1000 mAh battery as an example; if it was rated at 10C that would mean you could pull a maximum sustained load up to 10,000 milliamps or 10 amps off that battery (10 x 1000 milliamps = 10,000 milliamps or 10 amps). From a time stand point, this equals 166 mAh of draw a minute so the 1000 mAh pack would be exhausted in about 6 minutes.

Excellent link and example Thanks dxw00d! Now I get it.

You're welcome. There's some good stuff on that site.