Battery Runtime & Bank Config
How long will this bank last, and how do I wire it?
Free to use without an account. A free installer account adds saved work, A4 previews and branded PDF exports.
The battery tool answers two questions: how long will this bank run the load, and how should it be wired? Enter the battery voltage and capacity, the target system voltage and the load to get series and parallel strings, usable energy, runtime, discharge current and a wiring layout.
How the Battery Runtime & Bank Config works
Describe one battery
Enter the voltage and amp-hour rating of a single unit, then choose the chemistry so the default depth of discharge is sensible.
Set the system voltage and target capacity
The tool works out how many units go in series to reach the system voltage and how many strings run in parallel to reach the capacity you want.
Check runtime and current
Runtime uses usable energy after depth of discharge and efficiency. Discharge current tells you whether the bank is being worked harder than its BMS or wiring should allow.
Worked example
Four 51.2 V 100 Ah lithium batteries
Four units in parallel at 51.2 V, 90% depth of discharge, 95% efficiency and a 1,500 W load.
- 51.2 V, 400 Ah, 20.48 kWh nominal
- About 17.5 kWh usable
- Roughly 11.7 hours at 1.5 kW
- About 29 A discharge current
Assumptions and limits
- Capacity is nameplate capacity. Real capacity falls with age, temperature and high discharge rates.
- Depth of discharge and efficiency come from your inputs, not from a battery datasheet lookup.
- A battery BMS may limit charge and discharge current below what the calculation allows. Check the datasheet.
Frequently asked questions
How do I calculate solar battery runtime?
Enter the battery bank capacity, depth of discharge, inverter efficiency and connected load. The tool returns the usable energy and estimated runtime at that load.
Can the tool design a series and parallel bank?
Yes. Enter the battery voltage and capacity plus the target system voltage to get the series strings, parallel strings and total number of battery units.
Why does depth of discharge matter?
A lower usable depth of discharge protects battery life. Lithium banks usually allow a deeper discharge than lead-acid banks, so the same nameplate capacity gives different usable energy.
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Last updated 17 October 2026Maintained by Mishka Energy.
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