Battery Charge Time Calculator
Estimate the time required to fully charge a battery.
Ah
A
η
Typical values: Lead-Acid ~0.85, Lithium-ion ~0.95, NiMH ~0.70.
How to Calculate Battery Charge Time
To estimate the charging time, divide the battery capacity (Ah) by the charging current (Amps). However, no charging process is 100% efficient, so you must account for energy loss (heat).
Formula
Time(h) = Capacity(Ah) / (Current(A) × Efficiency)
Calculation Example
Question: You are charging a 100 Ah lead-acid battery with a 10 Amp charger. The efficiency is 85%. How long will it take?
Answer:
Time = 100 Ah / (10 A × 0.85) = 100 / 8.5 ≈ 11.76 Hours
Typical Charging Efficiencies
- Lithium-ion (Li-ion): 90% - 99% (Use 0.95)
- Lead-Acid (Flooded/AGM/Gel): 80% - 85% (Use 0.85)
- NiMH / NiCd: 60% - 70% (Use 0.70)