Battery Charging Time Calculator
How long a battery takes to charge, with the charge rate expressed as a C-rate.
Results
Hours
9.41
h
Minutes
565
Battery capacity
80.00
Ah
Ratio
0.100
What this tool does
Charging is never perfectly efficient, so the real time is longer than capacity divided by current — around 85 % efficiency is typical for lead-acid and above 95 % for lithium. The C-rate at the end tells you how hard you are pushing: 0.1 C is a gentle overnight charge, 1 C is a fast one.
Formula
t = capacity × (1 − load) ÷ (current × η)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
c | Battery capacity | Ah |
s | Percentage | % |
i | Charging current | A |
ef | Efficiency | % |
T | Hours | h |
M | Minutes | — |
AH | Battery capacity | Ah |
CR | Ratio | — |
Worked example
- Battery capacity100 Ah
- Percentage20 %
- Charging current10 A
- Efficiency85 %
- Hours9.41 h
- Minutes565
- Battery capacity80.00 Ah
- Ratio0.100
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.