BATTERY CALCULATORS
Battery Calculators
Engineering tools with the formula, a worked example and the limitations of each method. Results are estimates — the battery datasheet prevails.
Conversions
- Ah to Wh ConverterConvert battery charge (Ah) into stored energy (Wh) using the nominal voltage.
- Wh to Ah ConverterConvert stored energy (Wh) into amp-hours at a given voltage.
- Battery Capacity Unit ConverterConvert between mAh, Ah, coulombs, Wh and kWh. Energy units need a voltage.
Sizing & runtime
- Battery Capacity Calculator (Ah)Find the nominal amp-hour capacity you need to run a load for a given time, accounting for usable depth of discharge and inverter/conversion losses.
- Battery Bank Voltage & Capacity CalculatorGet the voltage, capacity and energy of a bank made of identical batteries in series strings connected in parallel.
- Series & Parallel Connection CalculatorTell us the bank you need; we compute how many batteries to wire in series and in parallel.
- Battery Runtime CalculatorEstimate how long a battery will power a load, with optional Peukert correction for lead-acid batteries.
- Electrical Consumption CalculatorAdd up to six devices to get daily energy (Wh) and daily amp-hours at your system voltage.
- 12 V, 24 V & 48 V Battery System CalculatorSize a battery bank for a 12, 24 or 48 V system and see how system voltage changes current.
Charging
- Battery Charging Time CalculatorEstimate how long a charger takes to bring a battery from one state of charge to another.
- Charging Current CalculatorGet a typical charging current range for your battery capacity and chemistry.
Vehicles, trucks & marine
- Cold Cranking Amps (CCA) CalculatorEstimate an orientative minimum CCA from engine displacement and compare it with your battery. The vehicle manufacturer's specification always takes priority.
- RV & Marine House Battery CalculatorSize the house (service) bank of a motorhome, camper or boat from daily consumption, days off-grid and chemistry. Optional solar replenishment.
- Truck & Heavy Equipment Battery Bank CalculatorSize the starting bank of a truck, bus, tractor or machine (12 V parallel or 24 V series-parallel) from cranking requirement and optional overnight hotel loads.
Four values that are often confused
- Nominal capacity (Ah)
- Charge a battery delivers under rated conditions, usually over 20 hours (C20) at 25 °C.
- Usable capacity
- The part of the nominal capacity you can use without damaging the battery — about 50% for lead-acid, 80–90% for LiFePO4.
- Cranking current (CCA)
- Current deliverable for a short time in the cold to start an engine. It measures power, not stored charge, and cannot be converted to Ah.
- Stored energy (Wh)
- Ah × voltage. The right unit to compare batteries of different voltages.