Battery Capacity Calculator
Quickly calculate battery capacity (Ah or Wh) and runtime for DC loads; includes conversions, depth-of-discharge, efficiency, series/parallel sizing, and worked examples.
battery capacity for inverter
To estimate battery capacity, load power (W 0) multiplied by runtime (h) equals energy in watt-hours. Divide the number of units of Wh by the system voltage to change units into ampere-hours. Efficiency and depth of discharge adjustment to size in the world.
Formula & Table Summary:
Energy (Wh): Wh = P_load × t
Ah from Wh: Ah = Wh ÷ V
Required Ah: Ah_req = (P_load × t) ÷ (V × DoD × η)
Runtime: t = (Ah_bat × V × DoD × η) ÷ P_load
battery storage kWh calculator
A battery capacity calculator is useful to calculate the size of a battery (in ampere-hours, Ah, or watt-hours, WH) required to provide power to an object over a specific time. Entering load power, runtime, voltage, depth of discharge (DoD), and efficiency will compute the size of the required battery. The equations give a relationship between Wh and Ah of battery storage. The tool can be effective in sizing batteries used in solar, backup, UPS, EV, or off-grid applications.
battery capacity calculator
| Scenario | Inputs | Result |
|---|---|---|
| Lamp 60W, 10h | 12V, DoD 50%, η 95% | Ah_req ≈ 105 → 120 Ah |
| Backup 300W, 4h | 24V, DoD 80%, η 90% | Ah_req ≈ 69 → 75 Ah |
| Solar 1kW, 2h | 48V, DoD 60%, η 88% | Ah_req ≈ 79 → 80–100 Ah |
| EV 20 kWh | 400V, DoD 90%, η 90% | Ah_req ≈ 62 Ah pack |
Frequently Asked Questions - Battery Capacity Calculator:
How do I convert Wh to Ah?
Ah = Wh ÷ V (where V is battery voltage).
How to size battery for a load?
Compute Wh = W×h, then Ah_req = Wh ÷ (V×DoD×η).
What is Depth of Discharge (DoD)?
DoD is the fraction of battery capacity you can safely use (e.g., 0.5 for 50%).
Why include efficiency?
Inverter/charge/discharge losses mean not all stored energy is usable; include η < 1.
How to get runtime from battery specs?
t = (Ah_bat × V × DoD × η) ÷ W_load.
How do series and parallel affect bank?
Series increases voltage, parallel increases Ah; combine for desired V and capacity.
What is C-rate?
C = I_load / Ah_bat; it indicates charge/discharge speed and affects capacity and life.
Should I round up battery size?
Yes — round up to nearest standard size and allow margin for aging and temperature effects.
How to size for solar charging?
Include days of autonomy, solar input, inverter losses, and charging efficiency in Wh needs.
Does temperature affect capacity?
Yes — cold reduces usable capacity; check manufacturer derating curves.
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