Battery Pack Configuration Calculator
Voltage, capacity and energy of a series-parallel pack, with the runtime and current at a given load.
Results
What this tool does
The notation 4S2P means four cells in series, two such strings in parallel: the series count multiplies the voltage, the parallel count multiplies the capacity, and the energy in watt-hours is the product of both — which is why two packs with the same watt-hours can behave completely differently. Watt-hours is also the number airlines and couriers regulate.
Formula
series adds the voltage, parallel adds the capacity
Variables
| Symbol | Meaning | Unit |
|---|---|---|
ss | Cells in series | — |
pp | Strings in parallel | — |
vc | Voltage per cell | V |
cc | Capacity per cell | mAh |
ld | Power | W |
VV | Voltage | V |
AH | Battery capacity | Ah |
WH | Energy | Wh |
NC | Cells in total | — |
RT | Hours | h |
IL | Current | A |
Worked example
- Cells in series4
- Strings in parallel2
- Voltage per cell3.7 V
- Capacity per cell3400 mAh
- Power50 W
- Voltage14.800 V
- Battery capacity6.8000 Ah
- Energy100.640 Wh
- Cells in total8
- Hours2.013 h
- Current3.378 A
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
Frequently asked questions
Why must the cells be matched?
Because in series the weakest cell sets the limit for the whole string: it empties first and, without protection, is then driven below its safe voltage by the others still pushing current through it. In parallel, cells at different states of charge dump current into each other the moment they are joined. Mixing ages, brands or capacities is how packs catch fire, which is why a battery management system is not optional on lithium.