Originally Posted by Slaanesh
However all this 'C' rating stuff is also a lot of marketing hype. Marketers love putting big numbers on their products!
A batteries REAL performance is given by it's internal resistance - which is seldom stated - however can be easily measured with a multimeter. Some LiPO chargers also have it notably the iCharger series.
C rating is somehow marketing .. but as well ... is the outcome of quality test as well ...
The battery is not a passive resistor, where internal resistance is constant (or function of the temperature) ... in a battery the load condition change the internal resistance.
The internal resistance measured by a charger can't be very accurate .. since measure the resistance for charge the battery ... while the C rating is based normally for the discharge.
If you see how the battery are tested, you will see that IR is not so relevant ... you will see that it will be mainly shown the voltage kept by the battery at different constant discharge ... for the full battery discharge time ... on top ... the measurement of the temperature of the battery is always reported by proper battery testing.
LiPo battery should never get more hot then ~60 deg ... so .. often the C rating is mainly due not only by the voltage drop, but the limit of overheat the battery during a discharge.
Anyhow ... the C rating in these days is relative accurate from the producers ... clearly they tend to be a bit optimistic on it, since the C rating measure also the quality of the battery on keep voltage under load.