75Ah to Wh — 900 Wh at 12V
75Ah stores 900 Wh at 12V, 1,800 Wh at 24V, and 3,600 Wh at 48V. Below: usable energy per chemistry, what it runs, and how the same energy is built from standard modules.
75Ah at 12V is 900 Wh — that is 0.9 kWh of nameplate energy.
Formula: Wh = Ah × V. The voltage is the nominal battery voltage, not the charging voltage.
A real LiFePO4 module of 75Ah is usually labelled 960 Wh, because its nominal voltage is 12.8V rather than a round 12V. Both 900 Wh and 960 Wh describe the same battery.
Result
Energy in Wh equals capacity in Ah multiplied by battery voltage. 1000 Wh equals 1 kWh.
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Design Your SystemAt every system voltage
The same capacity stores four times the energy at 48V that it does at 12V, and draws a quarter of the current for the same load.
| System voltage | Capacity | Energy | kWh |
|---|---|---|---|
| 12 V | 75 Ah | 900 Wh | 0.9 |
| 24 V | 75 Ah | 1,800 Wh | 1.8 |
| 48 V | 75 Ah | 3,600 Wh | 3.6 |
How much of it you can actually use
Nameplate energy is not usable energy. Depth of discharge caps what you may take out before you damage the battery, and it differs by chemistry.
| Chemistry | Depth of discharge | Usable energy | Usable capacity | Cycles at that DoD |
|---|---|---|---|---|
| LiFePO4 | 80 % | 720 Wh | 60 Ah | ~3,500 |
| AGM | 50 % | 450 Wh | 37.5 Ah | ~600 |
| Gel | 50 % | 450 Wh | 37.5 Ah | ~800 |
| Flooded lead-acid | 50 % | 450 Wh | 37.5 Ah | ~400 |
What that runs
Runtime from the usable LiFePO4 energy at 12V (80% depth of discharge), one load at a time, no inverter losses on the DC rows.
| Load | Power | Runtime |
|---|---|---|
| LED lighting | 15 W | 48 h |
| 12V compressor fridge (average) | 45 W | 16 h |
| Diesel heater (fan and glow plug average) | 30 W | 24 h |
| Water pump (while running) | 65 W | 11.1 h |
| Laptop plus router | 75 W | 9.6 h |
| Kettle through an inverter | 1200 W | 0.6 h |
What this size is in practice
75Ah is a legacy AGM and gel size, still fitted as the factory leisure battery in many caravans and older motorhomes. Owners usually meet this number when they consider replacing the original battery with lithium.
Building the same energy from standard modules
How many standard 100Ah 12V modules add up to this energy, and what capacity that becomes at each system voltage.
| System voltage | Capacity | Standard modules |
|---|---|---|
| 12 V | 75 Ah | 1 x 100Ah / 12V |
| 24 V | 37.5 Ah | 1 x 100Ah / 12V |
| 48 V | 18.8 Ah | 1 x 100Ah / 12V |
Other capacities (Ah)
Other energy values (Wh)
FAQ
How many Wh is 75Ah?
75Ah is 900 Wh at 12V, 1,800 Wh at 24V, and 3,600 Wh at 48V. Multiply the amp-hours by the nominal battery voltage: Wh = Ah × V.
How much of that 900 Wh can I use?
On LiFePO4 at 80% depth of discharge you get 720 Wh (60 Ah at 12V). On AGM or gel at 50% you get 450 Wh (37.5 Ah). Same nameplate, very different usable energy.
How long does that run a 12V fridge?
A compressor fridge averaging 45 W runs about 16 hours on the usable LiFePO4 energy at 12V. Cycling depends on ambient temperature, so treat this as the upper bound for a well-insulated unit.
Why does the datasheet say 960 Wh instead of 900 Wh?
Because LiFePO4 has a nominal voltage of 12.8V per 12V module, not exactly 12V. 75Ah × 12.8V = 960 Wh. The 12V figure of 900 Wh is the conservative system-voltage calculation. Both describe the same battery.
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