Solar & battery
Solar Charge Time Calculator
Charge time in amp hours, for systems specified in Ah rather than kWh.
Result
C rate is the charge current as a fraction of capacity, and every chemistry has a maximum. Lead acid should generally stay below 0.2C; lithium iron phosphate tolerates 0.5C and often more. Exceeding the manufacturer's limit shortens life and, on lithium, is a safety matter rather than a performance one.
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About this calculator
What is a C rate?
Charge or discharge current divided by capacity. A 100 Ah battery charged at 50 A is at 0.5C. Manufacturers publish a maximum, and it is worth respecting.
Can I charge lithium in the cold?
Not below freezing without a heater. Charging a cold lithium cell plates lithium metal onto the anode, which permanently damages it. Most quality batteries refuse to accept charge below about 0 degrees C.
The formula
hours = (capacity x depth of discharge / efficiency) / charge current
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