Charging Time
Charging
Enter capacity, charge current and efficiency; estimated time appears live.
Estimated charge time
How to use this calculator
Charging time is capacity divided by charge current, extended by losses: t = (Ah / I) / efficiency. Enter the capacity (Ah/mAh), the charge current (A/mA), and a charging efficiency (1–100%). The estimated real‑world time appears live, alongside the theoretical 100% figure so you can see how much the losses add.
What it means in a real circuit
Efficiency here covers the charger's conversion losses and the battery's own inefficiency — lead‑acid chargers are often 70–85% efficient, while Li‑ion through a good charger can be 90%+. The "theoretical" time assumes every amp‑hour in equals an amp‑hour out, which never happens. Use a realistic efficiency to avoid under‑estimating how long a charge takes, and remember the final top‑off (trickle) stage adds extra time that this estimate doesn't capture.