Home / Runtime calculator
How long will your JBD 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.
JBD boards protect packs of every size, so there is no typical capacity. The calculator starts with a 16S pack of 280 Ah cells (51.2 V, 14.34 kWh), a common home build. For a 12 V or 24 V pack, enter its capacity in kWh: volts × amp-hours ÷ 1000.
JBD 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 a 16S 280 Ah pack: 14.34 kWh, from 90 % to a 10 % cut-off, behind an inverter at 92 % that uses 35 W for itself, with an average draw of 400 W: 14.34 × 0.8 × 0.92 ÷ 0.435 ≈ 24 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.
Your appliances run on the sun, by themselves
JBD Monitor tells Home Assistant when the battery fills up and when it runs low. Four simple rules, and the washing machine, the water heater and the car use your sun instead of the grid. Watch a day:
Your solar production
Your consumption
Automations
- Washing machine on the sun
- The car follows the sun
- Hot water for free
- Gentle evening heating
Logbook
- Solar production
- House and heating
- Washing machine
- Water heater
- Electric car
- Battery level
- From the grid
- Sold to the grid for little
Simulation of a sunny day for a house with 5 kWp of panels, a 10 kWh battery, a car that needs 10 kWh and a water heater. The energy delivered to each appliance is the same in both scenarios; only the timing changes. Your figures depend on your system, your tariff and the weather.
Keep reading
Give your JBD BMS a permanent dashboard
Order JBD Monitor, shipped on 10 November 2026 and tested on a JBD smart BMS before it leaves.
Plug & play: working in about a minute