Convert Ah and kWh at any voltage.
Capacity to energy and back: cell voltage to 800 V platforms, all in one place.
The formula
Ah and kWh measure two different things. Ah is charge; kWh is energy. The bridge between them is voltage.
Use the pack nominal voltage, not its full-charge or empty value. LiFePO4 cells are nominally 3.2 V, so a 16S system is 51.2 V.
What Ah, kWh and voltage mean
- Ah (amp-hours)
- Charge: one amp of current sustained for one hour. Independent of voltage.
- Wh / kWh
- Energy. This is the unit used for system sizing, runtime estimates and LCOS math.
- Voltage (V)
- The bridge between charge and energy. Wh = Ah x V.
- SOC / DoD
- SOC is the percentage of capacity left; DoD is the percentage already discharged.
Common pack specs
| Application | Voltage | Capacity | Energy |
|---|---|---|---|
| 12V 100Ah lead-acid replacement | 12 V | 100 Ah | 1.2 kWh |
| 24V telecom backup | 24 V | 200 Ah | 4.8 kWh |
| 48V telecom rack | 48 V | 100 Ah | 4.8 kWh |
| Residential LiFePO4 module | 51.2 V | 100 Ah | 5.12 kWh |
| C&I storage module | 51.2 V | 280 Ah | 14.34 kWh |
| EV battery pack | 400 V | 150 Ah | 60 kWh |
FAQ
What's the difference between Ah and kWh?
Ah measures charge; kWh measures energy. To bridge them, multiply by system voltage: kWh = Ah x V / 1000.
What's the Ah to kWh formula?
kWh = (Ah x V) / 1000. Example: a 100 Ah pack on a 51.2 V LiFePO4 system stores 5.12 kWh of nameplate energy.
Why does my datasheet's kWh look slightly different?
Datasheet figures are nameplate. Real usable energy depends on the BMS SOC window, discharge C-rate, temperature, age and round-trip efficiency.
Should I use cell voltage or system voltage?
Use the pack nominal voltage when sizing a full system. Use cell voltage only when working out single-cell figures.
Need the pack behind the numbers?
Hua Power builds the cabinets, containers and residential packs these numbers come from. Tell us the kWh / Ah target and we will spec a product line that fits.