300Ah to Wh — 3,600 Wh at 12V
300Ah stores 3,600 Wh at 12V, 7,200 Wh at 24V, and 14,400 Wh at 48V. Below: usable energy per chemistry, what it runs, and how the same energy is built from standard modules.
300Ah at 12V is 3,600 Wh — that is 3.6 kWh of nameplate energy.
Formula: Wh = Ah × V. The voltage is the nominal battery voltage, not the charging voltage.
A real LiFePO4 module of 300Ah is usually labelled 3,840 Wh, because its nominal voltage is 12.8V rather than a round 12V. Both 3,600 Wh and 3,840 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 | 300 Ah | 3,600 Wh | 3.6 |
| 24 V | 300 Ah | 7,200 Wh | 7.2 |
| 48 V | 300 Ah | 14,400 Wh | 14.4 |
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 % | 2,880 Wh | 240 Ah | ~3,500 |
| AGM | 50 % | 1,800 Wh | 150 Ah | ~600 |
| Gel | 50 % | 1,800 Wh | 150 Ah | ~800 |
| Flooded lead-acid | 50 % | 1,800 Wh | 150 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 | 192 h |
| 12V compressor fridge (average) | 45 W | 64 h |
| Diesel heater (fan and glow plug average) | 30 W | 96 h |
| Water pump (while running) | 65 W | 44.3 h |
| Laptop plus router | 75 W | 38.4 h |
| Kettle through an inverter | 1200 W | 2.4 h |
What this size is in practice
300Ah is the large single module: liveaboard boats, full-time campers with air conditioning, and cabins that need to ride out a grey week. At 12V the bank current alone justifies a Class T fuse and 50mm2 or larger main cables.
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 | 300 Ah | 3 x 100Ah / 12V |
| 24 V | 150 Ah | 3 x 100Ah / 12V |
| 48 V | 75 Ah | 3 x 100Ah / 12V |
Other capacities (Ah)
Other energy values (Wh)
FAQ
How many Wh is 300Ah?
300Ah is 3,600 Wh at 12V, 7,200 Wh at 24V, and 14,400 Wh at 48V. Multiply the amp-hours by the nominal battery voltage: Wh = Ah × V.
How much of that 3,600 Wh can I use?
On LiFePO4 at 80% depth of discharge you get 2,880 Wh (240 Ah at 12V). On AGM or gel at 50% you get 1,800 Wh (150 Ah). Same nameplate, very different usable energy.
How long does that run a 12V fridge?
A compressor fridge averaging 45 W runs about 64 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 3,840 Wh instead of 3,600 Wh?
Because LiFePO4 has a nominal voltage of 12.8V per 12V module, not exactly 12V. 300Ah × 12.8V = 3,840 Wh. The 12V figure of 3,600 Wh is the conservative system-voltage calculation. Both describe the same battery.
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