Cell parameters
V
Li-Ion/LiPo: 3.7V nominal
mAh
S
Adds voltage
P
Adds capacity
Circuit diagram
Common configurations — click to load
Series vs Parallel rules
| Config | Voltage | Capacity | Energy | Use case |
|---|---|---|---|---|
| Series (nS) | V × n | C (same) | E × n | Higher voltage (motors, inverters) |
| Parallel (nP) | V (same) | C × n | E × n | Longer runtime, higher current |
| nSnP | V × S | C × P | E × S × P | Both higher voltage and capacity |
Important notes
Series packs — BMS required
- Cells in series must be balanced — slight differences grow over time
- Always use a BMS (Battery Management System) for Li-Ion/LiPo series packs
- BMS protects against overcharge, over-discharge, and short circuit
- Use a cell balancer / balancing charger for LiPo packs
Parallel packs
- Only parallel cells of the same chemistry, voltage, and ideally capacity
- Before connecting in parallel, make sure cells are at the same voltage (within 0.05V)
- Never connect a full cell to an empty cell — large inrush current
- Parallel cells self-balance continuously during use
Li-Ion / LiPo voltages
- Nominal: 3.7 V
- Fully charged: 4.2 V
- Cut-off (min): 3.0 V (never go below)
- 2S: 7.4V nom / 8.4V max / 6.0V min
- 3S: 11.1V nom / 12.6V max / 9.0V min
- 4S: 14.8V nom / 16.8V max / 12.0V min
Charge rate (C-rating)
1C = charge current equal to capacity in mAh.
Example: 3000 mAh cell at 1C = 3A charge rate.
For parallel packs: total 1C = capacity × P.
Most Li-Ion cells: safe at 0.5C–1C charge.
LiPo racing cells: up to 5C charge possible.