SolarMathKit

Battery wiring

Battery series and parallel calculator

Check a layout you already know, or solve for the smallest whole-battery layout that reaches a target voltage and capacity. The diagram shows topology, not installation detail.

Runs in your browserEditable assumptionsPlanning estimate

Inputs

Describe the battery layout

Calculation mode
Usable-energy assumptionsEditable planning values

Planning estimate

Your planning estimate

Local calculation

Enter your values, then calculate. Results will show the formula inputs and rounding used.

Formula used

total V = unit V × series; total Ah = unit Ah × parallel; total Wh = total V × total Ah

Series connections add voltage while amp-hours stay the same. Parallel strings add amp-hours while voltage stays the same. Total stored energy equals the resulting voltage multiplied by the resulting amp-hours.

See the full assumptions and rounding policy.

Worked example: four 12V 100Ah batteries

Arrange two batteries in each series string and connect two matching strings in parallel.

  1. Voltage: 12V × 2 in series = 24V.
  2. Capacity: 100Ah × 2 parallel strings = 200Ah.
  3. Energy: 24V × 200Ah = 4,800 Wh.
  4. Battery count: 2 series × 2 parallel = 4 batteries.
Result: A 2S × 2P layout produces a nominal 24V, 200Ah, 4.8 kWh bank.

Common mistakes to avoid

  • Adding amp-hours in a series string.
  • Adding voltage across parallel strings.
  • Mixing batteries with different voltage, capacity, chemistry, age, or health.
  • Using a topology sketch as a cable, fuse, or terminal-layout drawing.

Questions people ask

Does series or parallel create more energy?

No. With the same matching batteries, total Wh is the same. The arrangement changes the voltage and Ah relationship.

Why must target voltage be an exact multiple?

A fixed-voltage battery module can only create whole series steps. The calculator will not invent a fractional battery.

How many parallel strings are safe?

There is no universal number. Current sharing, busbar design, protection, monitoring, and manufacturer limits all matter, so the calculator reports the topology without declaring a construction threshold.

Before you build: This calculator is for planning. Check voltage limits, current limits, temperature corrections, protection devices, cable sizing, and installation rules against equipment manuals and a qualified professional.