Battery Bank Series & Parallel Builder

Turn an S×P battery layout into bank voltage, amp-hours, stored energy and estimated AC runtime.

Series vs parallel

Series wiring adds voltage while amp-hours stay the same. Parallel wiring keeps voltage the same while amp-hours add. Total stored energy is bank voltage × bank amp-hours, assuming identical batteries. For example, four 12.8V 100Ah batteries in series become a nominal 51.2V 100Ah bank, while four in parallel remain 12.8V but become 400Ah. Both arrangements contain approximately the same nominal watt-hours.

Why higher voltage changes current

For the same power, higher battery voltage reduces current. A 2,000W inverter supplied from roughly 12V requires far more DC current than the same power supplied from roughly 48V. That affects cable size, protection devices, voltage drop and BMS requirements. This builder calculates energy architecture only; it does not size conductors or overcurrent protection.

Important compatibility checks

Do not assume any battery can be connected in arbitrary series or parallel counts. The battery manufacturer must explicitly support the configuration, and the BMS, inverter, charger, fusing, cabling and disconnect equipment must all match the resulting voltage and current. Batteries in parallel should also follow the manufacturer’s guidance on model matching, state of charge and connection layout.

Runtime is separate from current capability

A bank can contain enough watt-hours for a long runtime and still be unable to supply the instantaneous current an inverter demands. Check battery and BMS continuous/peak discharge-current limits separately from this energy calculation. Then use the outage load planner to estimate the storage target your household actually needs.