Series vs Parallel Battery Calculator
Voltage, capacity, energy and internal resistance of any existing S×P battery arrangement — with sag at 1C computed.
Series-PARALLEL banks of lead-acid 12 V blocks (e.g. 2S2P of 12 V/100 Ah for 24 V/200 Ah) should be wired diagonally (take + from one corner, − from the opposite) so each string sees equal cable resistance. Never parallel batteries of different age/capacity — the strong one cycles the weak one and both die early. Lithium banks: one BMS per series string.
Series vs Parallel Battery Calculator computes voltage, capacity, energy and internal resistance of an existing battery arrangement — free, instant and private in your browser. Off-grid and RV builders combining batteries, and students learning pack behaviour use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Series vs Parallel Battery Calculator
Series vs Parallel Battery Calculator computes voltage, capacity, energy and internal resistance of an existing battery arrangement using the standard engineering relation: V = Ns·Vc; Ah = Mp·Ahc; R(pack) = Rc·Ns/Mp — and sag = I·R at load. Worked live: 2S2P of 12 V/100 Ah blocks gives 24 V/200 Ah with one quarter of one block's resistance per string-pair math. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Series vs Parallel Battery Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Series vs Parallel Battery Calculator?
- ✓Implements the real formula — V = Ns·Vc — with the substitution shown, not a black box
- ✓Built for off-grid and RV builders combining batteries, and students learning pack behaviour
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate series vs parallel battery?+
Voltage, capacity, energy and internal resistance of an existing battery arrangement follows V = Ns·Vc; Ah = Mp·Ahc; R(pack) = Rc·Ns/Mp — and sag = I·R at load. For example, 2S2P of 12 V/100 Ah blocks gives 24 V/200 Ah with one quarter of one block's resistance per string-pair math. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Series or parallel — which should I wire first?+
For lead-acid banks, build series strings then parallel the strings, taking + and − from diagonal corners so every path sees equal cable resistance. For lithium, parallel cells into groups first, then series the groups under one BMS — that's how commercial packs are made.
Why does pack voltage dip when the load kicks in?+
Internal resistance: sag = I × R(pack). Series stacks resistance, parallel divides it, so the same cells arranged 4S1P sag 16× more volts than 1S4P at equal power. If sag trips your inverter, more parallel paths or lower-resistance cells are the fix.
Is the Series vs Parallel Battery Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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