Note: Use our solar battery charge time calculatorto find out the battery charge time using solar panels. If the C-rating is mentioned as C/n (any number), in this case, C = 1. (E.g, C/2 = 1/2 = 0.5C). 1. C/2 = 0.5C 2. C/5 = 0.2C 3. C/10 = 0.1C 4. C/20 = 0.05C Generally, you will find the battery c rate on battery label or on the specs sheet of your battery. As you can see, the battery c rating is mentioned as "max. charge current" and "max. discharge current". The below chart shows the conversion of different c-ratings on batteries into charge/discharge time. Converting the C rate of your battery to time will let you know your battery's recommended charge and discharge time. Formula: C-rate in time (hours) = 1 ÷ C-rate Formula: C-rate in time (minutes) = (1 ÷ C-rate) × 60 Converting the C rate of your battery into amps will give you the recommended charge and discharge current (amps). Formula: Battery charge and discharge rate in amps = Battery.