10C 15C 20C Lipos - What does the C mean

How quickly a battery can discharge is it’s maximum current capacity. Current is generally rated in C’s for the battery. C is how long it takes to discharge the battery in fractions of an hour. For instance 1 C discharges the battery in 1/1 hours or 1 hour. 2C discharges the battery in ? or half an hour. All RC batteries are rated in milli Amp hours. If a battery is rated at 2000 mAh and you discharge it at 2000mA (or 2 amps, 1 amp = 1000mA) it will be completely discharged in one hour. The C rating of the battery is thus based on its capacity. A 2000mAh cell discharged a 2 amps is being discharged at 1C (2000mA x 1), a 2000mAh cell discharged at 6 amps is being discharged at 3C( 2000mA x 3). I think gen ace lipo battery is best choice, they are the proffessional manufacturer of Lipo battery.

Currently LiPo technology does not allow currents as high as NiCad or NiMH batteries do. For this reason, this many LiPo batteries are put in parallel to increase the present capacity of the battery pack. When 2 batteries are wired positive to positive and negative to negative they become like one battery with double the capacity. If you have 2 lipo 3s 5000mah and you wire them in parallel then the result is the same as 14000mAh cell. This 5000mAh cell has the same C rating as the original 2000mAh cells did. Thus if the 5000mAh cells could discharge at a maximum of 5C, or 10 amps then the new 4000mAh cell can also discharge at 5C or (4000mA x 5) 20 amps. This method of battery pack building allows us to use LiPo batteries at higher currents than single cells could produce.

The naming convention that allows you to decipher how many cells are in parallel and how many are in series is the XSXP method. The number in front of the S represents the number of series cells in the pack so 3S means it’s a 3 cell pack. The number in front of P means the number of cells in parallel. So a 3S4P pack of 2100mAh cells has a total of 12 cells inside. It will have the voltage of any other 3S lipo pack since the number of cells in series determines the voltage. It will have the current handling of 4 times the maximum C rating of the 12 individual cells. So say our 3S4P lipo pack had a maximum discharge of 6C. That means that it has a nominal voltage of 10.8 volts (3×3.6) and a maximum discharge rate of 50.4 amps (2100mAh x 6Cx4P ).

The maximum continuous current delivering capability of a RC cars battery can be determined by multiplying the C-Rate X (mah of battery).

A 2000mah, 20C battery would be capable of delivering 40000ma (40A).
A 2000mah, 25C battery would be capable of delivering 50000ma (50A).

That’s in a perfect world - however, there are no standards for how a manufacturer/vendor decides how to C-Rate their batteries. The big boys like Enerland probably do a good job of accurately descrbing the C-rate. Other pack makers may be another matter. They may call a real 15C pack a 25C pack in order to sell more. You just have to go by the RCG reports on the packs to get some idea on how accurate the C-rate is.

The other side of the coin is flight time. To get a 10 min flight, the average C-Rate draw needs to be 6C. A 20C pack operated at 20C will last a max of 3 min flight time and you’ll maybe get 50 cycles out of it at the best.

Here is a good rule of thumb to go by.

3min flight to 80% drain = 16c avg and it can peak 32c = use 30c+
4min flight to 80% drain = 12c avg and it can peak 24c = use 25c+
5min flight to 80% drain = 10c avg and it can peak 20c = use 20c+
6min flight to 80% drain = 8c avg and it can peak 16c = use 15-20c+
7min flight to 80% drain = 7c avg and it can peak 14c = use 15c+

For me, high C-rates (>15) have no value as I want at least 8-10 min flight time. However, I’ll take them if the price differential is small as it generally means a battery with a lower IR.