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LiPo Battery C Rating Confusion

by Charles
(Nottingham, England)

Hi - firstly may I say that I've found the information on your web site the most comprehensive and understandable that I've found on the web.

I'm new to RC modelling although I have a background in electronics. I'm starting from scratch to look at a model hovercraft, the SRN1 - the first ever. I'm trying to understand about motor selection and all that goes with it.

Obviously articles are geared to aeroplanes and not hovercraft - but that's what I'm researching at the moment.

Anyway, my question - in the article about LiPos there's the following paragraph -

For example, this 2200mah LiPo battery pack with a 30C rating can safely provide 30 x 2200mah = 66,000 mA or 66 amps.

Sorry, I can't see where the "C" figure fits in here. The figure 2200mah is the capacity of the battery, i.e. 2200 milliAmps / hour. It would supply 2200 milliAmps for an hour or 1100 milliAmps for 2 hours, etc.

I can't see that multiplying the capacity, in units of mah, would give a result measured in Amps. What unit is the "C" figure?

Sorry if this sounds a bit confused, any comment/assistance would be very much appreciated. thank you.

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C Rating Units
by: Matt

Hi Charles,

I think you may be over thinking what "C Rating" really means.

Simply put the "C rating" is a number that helps you to determine the maximum sustained current you can draw from a particular battery without causing any damage to the battery.

I never really thought of "C rating" as having units. If it were to have units I suppose it would be 1/time or 1/h in this case.

I hope this helps...

by: Charles

Hi Matt - thanks, that sorts it for me. Perhaps I'm looking for too many problems.

A "C" rating caution
by: Quorneng

"C" is a discharge rate.
1C is the rate that would discharge the battery completely in one hour regardless of its size.

All batteries suffer damage if they are discharged too fast.
Strictly the battery manufacturer should state it as the "Maximum C" for any particular battery but for convenience the published C is assumed to be the maximum.

It worth remembering there is no "specification" concerning the effects of actually using a particular C discharge rate so you are in the hands of the manufacturer.
There is always the risk they claim a higher than realistic C rating to help "sell" a battery!

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