Cuts out under load

Possible causes

General, component-based causes – not a manufacturer-specific statement.

• Aged cells, increased internal resistance
• Weak or discharged cell group
• Contact fault at battery connector/mount
• BMS protection or BMS fault

Safe test steps

• Resting voltage at the pack output vs. the nominal class (S × 3.6 V nominal, S × 4.20 V full for Li-ion).
• Load test with current: R = ΔU / I (E-Bike Doctor battery calculator).
• Condition of mount contacts, discoloration, play.

Workshop reference values

• Li-ion cell: 3.6–3.7 V nominal, 4.20 V full; manufacturer minimum typically 2.5–3.0 V (per datasheet).
• Pack full voltage (Li-ion): 7S 29.4 V · 10S 42.0 V · 13S 54.6 V · 14S 58.8 V.

Repair approach

• Full charge with the original charger, then re-measure.
• Pack repair/re-celling only by a qualified battery shop with identical matched cells; otherwise replace the pack.

Tools needed

• Digital multimeter (CAT III, fused inputs)
• Fused load tester or clamp meter
• Manufacturer dealer diagnostic tool/software (if available)