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Battery C-rating

Hi everyone! I'm now in the situation where I have to choose a battery for the airplane I'm building. The battery will run one motor which draws a maximum of 20A and all the servos (about 3A in total) . I would like its capacity to be around 2500 mAh. The battery will have to be able to output at least 25A at a time. Does this mean that it must have a C-rating of 25? Or how does the C-rating work?

Thank you.


Elite member
The C-Rating is basically just a multiple of the mah. It is how many amps the battery can push out at a time. So if you need 25 amps to run everything, and you have a 2500mah battery, you would need a 10 C battery or higher. (10x2.5mah=25 amps.)


Elite member
Take the c rating with a grain of salt, as they say. The c rating is often used as an advertising ploy as well. Consider a 3000mah battery with 100c rating. If I do the math I "should" be able to pull 300a continuous from it. I wouldn't try that. :). But in general the higher c rating the better the battery and higher continuous currents you can pull. I find 25c is fine for my uses. I only draw about 35a at most. For now. But keep in mind as well the smaller mah rated the battery is you may need higher c rating. The whole thing is a bit muddy in reality


Elite member
there is a formula to find true c rating. it uses the internal resistance. which you can get from some chargers. ill see if I can find it again.