Battery Charging Time Calculator for Inverter and Lithium Batteries
Enter battery Ah, the charger current and how much of the battery is empty. You get the charging time and whether the charge rate suits the battery.
- Nothing you type is stored
- Free
- No signup
Charging time
10 h 00 min
Suitable charge rate- In hours
- 10 h
- Charge to put back
- 120 Ah
- Charge rate
- C/10
Estimate only. Real results depend on your equipment, its age and conditions.
Lead-acid: about 80% efficiency; the last 10–20% (absorption) takes extra time.
Show working
- 150 × 0.8 = 120 Ah
- 120 ÷ (15 × 0.8) = 10 h
How to use
- Choose lead-acid (inverter/tubular) or lithium.
- Enter battery capacity in Ah and charger current in A.
- Enter how empty the battery is to see the time.
Good to know
Time (hours) = Ah to refill ÷ (charging current × charge efficiency). Lead-acid batteries lose energy to heat and gassing, so about 80% efficiency is used; lithium about 95%. 150 Ah, 80% empty at 15 A: 120 ÷ (15 × 0.8) = 10 hours.
Lead-acid chargers slow down near full (absorption stage), so the last 10–20% takes extra time. Inverter batteries are usually charged at about C/10 (10% of Ah in amps); much faster heats and shortens life, much slower may not fully charge between power cuts.
Lithium (LiFePO4) batteries accept higher currents (often up to 0.5C) and charge more linearly. Always follow the battery maker’s charging current and voltage limits.
Questions
How long does a 150 Ah battery take to charge?
From 80% empty at 15 A, about 10 hours for lead-acid. At 10 A, about 15 hours.
What charging current is best for an inverter battery?
About 10–15% of Ah, e.g. 15–20 A for a 150 Ah tubular battery.
Why does charging slow down at the end?
Lead-acid chargers reduce current near full to avoid gassing; this absorption stage adds time.
Is a lithium battery faster to charge?
Yes. It is more efficient and accepts higher current, within the maker’s limits.
What does C/10 mean?
A current equal to one tenth of the Ah rating: 15 A for a 150 Ah battery.