Electronics · battery dc power
Battery Series–Parallel Calculator
Calculate voltage, amp-hours, watt-hours and battery count for one explicit arrangement of identical units.
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Calculate one series/parallel battery topology
See how identical-unit voltage, Ah and total Wh change with an explicit topology.
Example arithmetic values are preloaded to demonstrate the topology relationship. They are not a battery or wiring recommendation.
24 V × 300 Ah
Show calculation steps
| Step | Expression | Raw value |
|---|---|---|
| Bank voltage | unit V × series | 24 V |
| Bank capacity | unit Ah × parallel | 300 Ah |
| Bank energy | bank V × bank Ah | 7,200 Wh |
How to use this calculator
Enter the nominal voltage and rated Ah of one identical battery, the units in each series string, and the number of parallel strings. The calculator reports bank voltage, bank Ah, nominal Wh and total unit count.
bank voltage = unit voltage × series count
bank Ah = unit Ah × parallel count
battery count = series count × parallel count
bank Wh = bank voltage × bank Ah
Understanding series and parallel
Series raises voltage in this arithmetic model while the Ah of a string stays equal to one unit. Parallel adds identical string capacities while voltage stays equal to one string. A 2S3P bank made from 12 V, 100 Ah units is 24 V, 300 Ah, 7,200 nominal Wh and contains six units.
The energy identity is also unit V × unit Ah × total count. Rearranging the same number of identical batteries changes the voltage/Ah split but not their combined nominal Wh.
What this tool deliberately does not decide
This page does not approve mixing battery chemistry, model, capacity, state of charge, age or condition. It does not check permitted series count, permitted parallel count, BMS architecture, balancing, fault current, conductor, disconnect, fuse, charger or enclosure requirements. Current exact-product instructions and qualified electrical review control those decisions.
Common mistakes
- Adding Ah for series-connected units.
- Adding voltage for parallel-connected strings.
- Comparing banks only by Ah while ignoring voltage.
- Assuming that an arithmetic topology is a permitted product topology.
- Mixing unlike units because their label voltages appear equal.
- Using nominal Wh as fully usable Wh.
Frequently asked questions
Does series increase runtime?
It changes voltage. Runtime depends on total usable energy and battery-side load, including conversion losses and cutoffs.
Does parallel increase capacity?
For identical compatible strings, the arithmetic Ah sum increases. Whether a product may be paralleled and how it must be protected are separate questions.
Why are the counts limited?
The tool accepts whole numbers from 1 to 1,000 to reject accidental decimals and unreasonable browser inputs. That limit is not an installation approval.
Use the result in the battery runtime calculator or work backward with the battery capacity calculator, while retaining the same safety boundaries.
References and further reading
These sources define or explain the calculation. Source editions and model limits are part of the result—not decorative citations.
- Battery capacity and Peukert exponent, Victron Energy; accessed 2026-08-22. BAT-C01
- DOE Explains...Batteries, U.S. Department of Energy; accessed 2026-08-22. BAT-C03
- NIST Guide to the SI, National Institute of Standards and Technology; accessed 2026-08-22. BAT-C04