Duration is more than a formula—it is whether your charge window fits the trip. This battery charge duration estimator walks through capacity, charger rate, and efficiency to estimate how long until the pack is ready again.
Benefits
- Estimates full-charge duration from mAh ÷ mA with efficiency margin.
- Scales for partial refill: duration × (mAh_needed ÷ capacity).
- Documents taper and heat loss via efficiency %—not false precision.
How it works
- Enter total pack mAh (or Ah × 1,000) and usable charger mA.
- Set efficiency 85–95% when taper and heat apply; 100% for ideal CC only.
- Read duration—compare to available shore, solar, or generator hours.
FAQ
What does a battery charge duration estimator do?
It projects how many hours a charge session lasts: mAh ÷ mA ÷ (efficiency ÷ 100). Example: 20,000 mAh at 4,000 mA and 90% efficiency → 20,000 ÷ 4,000 ÷ 0.9 ≈ 5.56 hours. Use it to see if an 8-hour overnight window can finish a depleted bank.
How do I estimate duration for a partial charge?
Multiply full duration by the fraction of capacity needed. Need 50% of a 10,000 mAh pack? Use 5,000 mAh effective in the formula—or run full capacity and halve the result. Add efficiency if the top-up segment still tapers.
Why is estimated duration longer than mAh ÷ mA?
Chargers taper current near full SoC; heat wastes energy; BMS may pause on temperature. Lower efficiency in the estimator stretches duration to match field experience—better for schedules than assuming 100% constant current.
Technical specifications
- Full duration_h = mAh ÷ mA ÷ (efficiency% ÷ 100).
- Partial duration ≈ full_duration × (mAh_to_add ÷ total_mAh).
- Planning buffer: +10–15% beyond estimate for cold or aged packs.
- Related: battery-charging-time-calculator, battery-runtime, solar-panel-size.