LIPO Packs C rating in parallel

I have a question about lipo pack's C rating when wired in parallel.

I want to know if the overall C rating goes up if you hook up two or more batteries in parallel assuming that the batteries have the same specs. Or, does the over all C rating of lipo cells wired in parallel actually stay constant?

In other words, do you add the C ratings together for each cell just like you would do with current?


Matt's Reply:Let's work through it...

That's a good questions.

You're making my brain hurt, lol.

OK, lets assume we have one 20C 1800mah battery.

Tha maximum safe discharge rate for one cell would be:
20 x 1800mah = 36 amps

So if you have three 20C 18mah batteries in parallel you could safely discharge:
3 x 36Amps = 108 amps

The capacity of three 20C batteries in parallel would be:
3 x 1800mah= 5.4 amps

If the total capacity of the pack is 5.4 amps and the maximum safe discharge is 108 amps then the C rating for the entire pack would be:

108 amps divided by 5.4 amps = 20C

So the C rating is 20 for the entire pack.

So, to answer your questions. You do not add the C ratings together. The total C rating for batteries in parallel remains the same as each individual cell.

So what about the overall C rating when adding in series?

The capacity of three 20C 1800mah cells in series is:
1800 mah

The maximum safe discharge of the entire pack is:
20x1800mah= 36amps

The total C rating of the entire pack is:
36amps divided by 1800mah= 20C

So we just proved that you don't add the C rating when adding in series either.

This is some deep thoughts... I feel like I'm back in high school doing geometry proof's, lol.