Battery Charging Time Calculator

Enter the battery details and the charger output voltage and current. The calculator estimates the charging time (including the slower final stage) and checks whether the charger voltage suits this battery type.

Result

Approximate charging time
Energy drawn from the mains	Wh
Charger power	W
Charging current relative to the battery	C
Suitable charger voltage for this battery	V

Results are calculated estimates. Always check your vehicle manufacturer's instructions.

Matching products: Battery chargers Batteries

How to use

Choose the battery type and enter the battery voltage (V) and capacity (Ah).
Enter the charger output voltage and current – you will find them on the charger label (e.g. 84 V 2 A).
Choose the percentage you are charging from and to. Do not leave a battery empty – a lead-acid battery is quickly damaged by deep discharge.

Frequently asked questions

Why do the last few percent charge so slowly?

Near the end of charging the charger switches to constant-voltage mode and the current gradually falls so the battery is not overcharged. On a lithium battery this starts at around 80%, on a lead-acid battery already at 70%.

Can I use a charger with a higher current?

Lithium batteries usually tolerate up to 0.5–1 C (10–20 A for a 20 Ah battery), lead-acid batteries about 0.1–0.3 C. The charger voltage must always match the battery type and voltage.

Why is the charger voltage higher than the battery voltage?

The nominal battery voltage is the average operating voltage. A full charge needs a higher voltage: for example, a 72 V lithium battery (20 cells) is charged to 84 V, and a 72 V lead-acid battery (6 × 12 V) to about 86–88 V.

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