About this replacement
Wella Bella, Super, Chromini & Contura HS40 — 1.2V Ni-MH Replacement Battery (WM1590-7290)
This is a 1.2V, 700mAh Ni-MH rechargeable cell for the Wella Bella, Super, Chromini, and Contura HS40 cordless shavers. It replaces the original internal battery when charge capacity has degraded. Voltage and cell format match the OEM specification directly.
- Shared platform — Bella, Super, Chromini, Contura HS40: These models run from the same 1.2V single-cell Ni-MH architecture with identical connector pitch and BMS handshake thresholds, so one cell covers the full range without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Bella platform. The BMS accepted the cell without fault flags, and termination voltage held at the expected 1.0V cutoff under shaver motor load.
- Charging port care after wet shaving: After rinsing the shaver head, dry the charging port completely before seating it in the dock — moisture bridging the two dock contacts causes the BMS to trip a protection fault that the device reports as a dead battery rather than a charging error.
Capacity fade from daily partial charging on the Wella Bella
Ni-MH cells used in small shavers are vulnerable to voltage depression when they are recharged every day without being fully discharged first. The cell's charge indicator drifts, so the shaver appears to have a full battery but cuts out earlier each week. This is not a dock fault — it is a cell-level issue. Running the shaver to full cutoff before recharging resets the usable capacity range and re-aligns the indicator.
Shaver motor speed dropping before the low-battery indicator lights
Under shaver motor load, the 1.2V Ni-MH cell's terminal voltage sags before the BMS reaches its cutoff threshold. The motor slows noticeably — pulling resistance increases, the shave feels laboured — but the indicator has not yet triggered. This is voltage sag under load, not a faulty indicator. If the motor recovers speed when the shaver is rested briefly, the cell is approaching end of life. Replace the cell when resting voltage no longer recovers above 1.1V.