Battery Basics
How you wire cells together decides your pack's voltage, capacity, and current. Here's the difference — with examples you can open and simulate.
Connect cells end to end — the positive terminal of one to the negative of the next, like links in a chain. Their voltages add, but the pack still holds the same amp-hours and current rating as a single cell.
Connect all the positives together and all the negatives together. Voltage stays the same as one cell, but capacity and maximum current multiply by the number of cells. Always join cells that are already at the same voltage.
Almost every pack combines both. The notation 13S4P means 13 cells in series, 4 in parallel — 52 cells total.
Each of these opens in the CellBench simulator with real discharge data — change the S and P counts and watch voltage, capacity, and runtime update live.
13S4P
Voltage: 47V nominal
Capacity: 12Ah / 562Wh
Classic 48V ebike pack. 13 in series for voltage, 4 in parallel for range.
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14S5P
Voltage: 50V nominal
Capacity: 25Ah / 1260Wh
52V long-range pack. More parallel groups = more capacity, same voltage.
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7S2P
Voltage: 25V nominal
Capacity: 8.4Ah / 212Wh
Smaller 24V pack — high-current cells in a compact series-parallel layout.
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Your motor, controller, or inverter needs a target voltage. Divide it by the cell's nominal voltage (about 3.6V for most Li-ion). A 48V ebike → 13S; a 36V → 10S; a 24V → 7S.
More parallel groups mean more capacity (longer runtime) and more current headroom. Check that P × the cell's continuous-current rating comfortably exceeds your peak draw.
Datasheet capacity assumes a gentle discharge. At high current, voltage sags and usable capacity drops. This is where simulating with real discharge curves beats back-of-envelope Wh math.
Build parallel groups first (they self-balance), then wire groups in series with a BMS sized for your S count and current. Use identical cells throughout.
Series increases voltage. Wiring cells in series (positive to negative, like links in a chain) adds their voltages together while capacity (amp-hours) and maximum continuous current stay the same as a single cell. Four 3.6V cells in series make a 14.4V battery with the same Ah as one cell.
No. Parallel wiring keeps voltage the same as a single cell and instead adds capacity (amp-hours) and maximum current. Four 3.0Ah / 15A cells in parallel give 12.0Ah and 60A at the same 3.6V nominal voltage. Parallel groups must be the same voltage before connecting, or large balancing currents will flow.
13S4P describes a pack with 13 cells in series (the 'S') and 4 cells in parallel (the 'P'), for 52 cells total. The 13S sets the voltage (13 × 3.6V ≈ 47V nominal) and the 4P sets the capacity and current (4 × 3.0Ah = 12Ah, 4 × 15A = 60A). Packs are almost always written in this S-then-P shorthand.
Neither is 'better' — they do different jobs. Series gives you the voltage your motor or inverter needs; parallel gives you the runtime and current. Real packs combine both (series-parallel) to hit a target voltage and capacity at once. The right split depends on your device's voltage and how long it needs to run.
Yes — that is exactly what a series-parallel pack is. The safe rule is to use identical cells (same model, ideally the same batch and state of charge) throughout, build the parallel groups first so each group self-balances, then connect the groups in series. Never mix different chemistries, capacities, or ages in one pack.
In a series stack, individual cells (or parallel groups) can drift to slightly different voltages over many cycles. A Battery Management System monitors each series group and balances them, and cuts off charge/discharge before any group is over- or under-voltage. Parallel cells within a group self-balance and share one BMS sense wire.
Pick a cell, set your S and P, and see real voltage, capacity, and runtime instantly. No account required.