Ah and Wh
Wh = V × Ah; 1 kWh = 1,000 Wh
Compare Wh, not Ah alone, when battery voltages differ.
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Find V and Ah on your LiFePO4 battery label, then add the watts your equipment uses. We will estimate how many hours it can run continuously.
Use the numbers on your battery and device labels. Measured power is even better if you have it.
If you have a capacity range, you can check it against the voltage, current and size of listed batteries.
Automatic matching covers deep-cycle use only. Starting, dual-purpose, regulated and other special uses need an engineering review. Also confirm charging, wiring, current sharing, dimensions, polarity and installation before choosing a battery.
Battery size depends on energy use, usable capacity and losses. Current limits and startup loads need a separate check.
Wh = V × Ah; 1 kWh = 1,000 Wh
Compare Wh, not Ah alone, when battery voltages differ.
Wh = Σ(W × hours × quantity × duty cycle)
A Wh input is already the total energy used during the selected period.
DC Wh ÷ DC efficiency + AC Wh ÷ inverter efficiency + standby Wh
DC devices and AC devices have different supply losses.
Required Wh = battery-side Wh × (1 + reserve) ÷ (DoD × temperature × health)
Less usable capacity means a larger battery is needed for the same load.
Runtime h = planned usable Wh ÷ average battery-side W
Temperature, ageing, duty cycle and conversion losses affect actual runtime.
A ≈ simultaneous battery-side W ÷ minimum working V
If the lowest operating voltage is unknown, the estimate uses 90% of nominal voltage.
Compare surge, inverter and BMS ratings at the same duration
A 5-second peak rating does not confirm that a longer surge is supported.
h = replace Wh ÷ (V × net charge A × efficiency) × completion factor
Nominal defaults: 95% charging efficiency and a 1.10 end-of-charge time factor.
Delivered Wh = nominal Wh × DoD × temperature × health × rate factor
Measured usable energy takes priority. There is no fixed Ah conversion ratio.
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