Chemistry decides the settings, not the board
Technical review pending — checked against public standards on
- chemistry
- configuration
The same BMS on LiFePO4 and on NMC needs completely different voltage thresholds. Using one profile on the other chemistry damages cells quietly.
A BMS is chemistry-agnostic hardware running chemistry-specific settings. The board does not know what cells are attached. Every protection threshold is a number you or a profile supplied, and a wrong number does not announce itself.
The three numbers that matter per cell
| Chemistry | Nominal | Charge cutoff | Discharge cutoff | Typical float |
|---|---|---|---|---|
| LiFePO4 | 3.20 V | 3.65 V | 2.50 V | 3.35–3.40 V |
| Li-ion NMC | 3.70 V | 4.20 V | 3.00 V | 4.05–4.10 V |
| LTO | 2.30 V | 2.80 V | 1.50 V | 2.60–2.70 V |
Multiply by series count to get pack thresholds. A 16 series LiFePO4 pack charges to 58.4 V; a 16 series NMC pack charges to 67.2 V. Same board, same wiring, 8.8 V apart.
Low-temperature charging is chemistry-specific too
Charging below 0 °C plates lithium metal on the anode. LiFePO4 tolerates slightly lower temperatures than NMC before this becomes significant, but none of them like it. This is why a charge-disable temperature input is not optional in a cold-climate installation — and why the sensor has to be on the cells, not on the board.
A board sitting at 15 °C inside an insulated box tells you nothing about cells at −5 °C.
Where the profiles differ in ways people miss
- Rebulk / restart voltage — how far the pack must fall before charging resumes. Too tight and the charger cycles constantly at the top; too loose and the pack sits partly discharged.
- Cell-difference alarm — LiFePO4 holds a very flat curve, so a small voltage difference means a large state-of-charge difference near mid-charge. A threshold that is fine on NMC is too loose on LiFePO4.
- Balance trigger — whether balancing runs only above a voltage threshold or whenever the board is powered. On LiFePO4 the flat curve makes voltage-triggered balancing less informative.
- Peak current duration — chemistry affects how much surge the cells themselves tolerate, independent of what the board allows.
Practical sequence for a new pack
- Confirm the chemistry from the cell datasheet, not from the pack label or the seller
- Set per-cell thresholds from that datasheet, then let the board compute pack thresholds
- Set the temperature charge-disable input, with the sensor on the cells
- Verify the sense wiring reads one cell voltage per adjacent pair before connecting
- Charge slowly the first time and watch per-cell voltages, not just the pack total
