Battery Charge Time Calculator
Fill in the values and the answer updates as you type.
How the Battery Charge Time Calculator works
Charge time = amp-hours to add ÷ (charger current × efficiency). Charging slows near full because chargers taper current in the final stage, so the last 10–20% takes longer than this simple estimate shows. Example: with the default values, charge time comes to 9.4 hours.
Inputs and results
The Battery Charge Time Calculator takes 6 inputs and gives 3 results.
What you enter
- Battery capacity (Ah) — starts at 100.
- Battery voltage (V) — starts at 12.
- Current charge level (%) — starts at 20.
- Target charge level (%) — starts at 100.
- Charger current (A) — starts at 10.
- Charging efficiency (%) — starts at 85.
What you get
- Charge time (hours)
- Charge to add (Ah)
- Energy to add (Wh)
Example: Battery Charge Time Calculator with the starting values
With battery capacity 100 Ah, battery voltage 12 V, current charge level 20 %, target charge level 100 % and charger current 10 A, the calculator returns:
| Charge time (hours) | 9.4 |
|---|---|
| Charge to add (Ah) | 80 |
| Energy to add (Wh) | 960 |
Change any value above and the results update straight away.
Battery Charge Time Calculator FAQ
How do I use the Battery Charge Time Calculator?
Enter battery capacity, battery voltage, current charge level and target charge level in the fields, then read charge time (hours), charge to add (ah) and energy to add (wh) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Battery Charge Time Calculator calculate?
Estimate how long a battery takes to charge. It returns charge time (hours), charge to add (ah) and energy to add (wh) from the 6 values you provide.
What values does the Battery Charge Time Calculator start with?
It opens with battery capacity 100 Ah, battery voltage 12 V, current charge level 20 % and target charge level 100 % so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Battery Charge Time Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Battery Charge Time Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.