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How long will your BSLBATT battery last?
Enter your system and your average consumption: the calculator gives the usable energy, the hours of autonomy and the time the batteries reach your cut-off.
BSLBATT makes 48 V batteries in several sizes: 5.12 kWh rack modules and wall units of around 10 kWh are common. The calculator starts with one 10.24 kWh battery. Adjust it to the label on yours.
BSLBATT Monitor does this calculation live, with your real consumption: the dashboard shows when the batteries will be full or reach your cut-off. See it in the demo →
The formula
autonomy = capacity × health × (charge − cut-off) × efficiency ÷ (consumption + inverter’s own consumption)
Example with one 10.24 kWh BSLBATT battery: from 90 % to a 10 % cut-off, behind an inverter at 92 % that uses 40 W for itself, with the house drawing 500 W on average: 10.24 × 0.8 × 0.92 ÷ 0.54 ≈ 14 hours.
Why real runtime is often shorter
- One weak cell ends the discharge. The BMS stops the battery when its lowest cell reaches its limit, even if the others still hold energy. A growing cell spread shortens the night.
- The displayed charge drifts. The state of charge is counted, not measured: without a full charge from time to time, it can be several points off.
- Cold reduces what you can take out. Below about 10 °C a lithium battery delivers less, and many BMS limit the current.
- Peaks cost more than the average. A kettle or a pump at 2 kW for a few minutes weighs more than its share, because of losses and current limits.
Typical night consumption in a home is 100 to 250 W; in the evening, 400 to 1,000 W. Your own figure is on the dashboard of your box after a few days.
Keep reading
Give your BSLBATT system a second pair of eyes
Order BSLBATT Monitor. Ships on 10 November 2026, tested on BSLBATT batteries.