BMS PCB Trace Width Calculator
The B−→FET→P− channel sized for pack current in still air — with balance-lead, Kelvin-shunt and FET-pour rules.
Preset for this niche — adjust to your stack-up. IPC-2221 assumes still air; verify hot paths with a thermal camera.
BMS Trace Width Calculator computes copper for the battery-management current channel that lives in still air — free, instant and private in your browser. Pack builders and BMS designers for e-bikes, scooters and storage 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 BMS PCB Trace Width Calculator
BMS Trace Width Calculator computes copper for the battery-management current channel that lives in still air using the standard engineering relation: IPC-2221 with BMS presets: 10 A, 15 °C rise, 2 oz copper — the FET pour doubles as the only heatsink. Worked live: a 10 A pack's B−→FET→P− channel wants ~4 mm minimum; production boards flood the full width. 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 BMS PCB Trace Width 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 BMS PCB Trace Width Calculator?
- ✓Implements the real formula — IPC-2221 with BMS presets: 10 A, 15 °C rise, 2 oz copper — the FET pour doubles as the only heatsink — with the substitution shown, not a black box
- ✓Built for pack builders and BMS designers for e-bikes, scooters and storage
- ✓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 bms trace width?+
Copper for the battery-management current channel that lives in still air follows IPC-2221 with BMS presets: 10 A, 15 °C rise, 2 oz copper — the FET pour doubles as the only heatsink. For example, a 10 A pack's B−→FET→P− channel wants ~4 mm minimum; production boards flood the full width. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why is the balance connector the most dangerous part of a BMS?+
Wiring order: each balance input expects one cell-step of voltage; a swapped or offset plug applies multiple cells across circuits rated for one — instant chip damage, occasionally fire. Verify the harness pin-by-pin with a meter against the board's silkscreen BEFORE plugging in, every time.
Charge and discharge FETs — why does my BMS have two banks?+
Back-to-back FETs let the BMS block each direction independently: over-discharge protection opens the discharge bank while still allowing charge, and vice versa. Both banks sit in the main current path, which is why their combined Rds(on) and the pour cooling them dominate BMS heating.
Is the BMS Trace Width 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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