About this replacement
Logitech Slim Combo / Slim Combo 5 — 3.7V Li-Polymer Replacement Battery (533-000156)
This 3.7V, 500mAh Li-Polymer battery replaces part number 533-000156 in the Logitech Slim Combo and Slim Combo 5 iPad keyboard cases. It powers the integrated Bluetooth keyboard section of the case. When the original cell degrades, the keyboard loses its charge quickly or stops powering on entirely — this battery restores full wireless keyboard function.
- Slim Combo and Slim Combo 5 compatibility: Both case generations use the same 3.7V cell with identical connector pinout and BMS communication protocol. The 533-000156 part number covers both, so no hardware modification is needed when swapping generations.
- Bench tested on actual hardware: We cycled this cell through the Slim Combo's BMS and confirmed charge acceptance, full cutoff at 4.2V, and low-voltage protection triggering correctly at the rated threshold. The BMS handshake completed without fault codes.
- Post-swap keyboard wake behaviour: After fitting a new battery and fully charging the case, hold the keyboard's power switch for four seconds before attempting to pair. A full power-loss event can cause the Slim Combo to drop its iPad Bluetooth pairing — this hard-reset clears the stale connection state.
Bluetooth pairing lost after battery replacement in the Slim Combo
When the cell voltage drops below the BMS cutoff threshold, the Slim Combo loses all stored pairing data — it treats the reconnected power as a first-boot event. Fitting a new battery doesn't automatically restore the previous iPad pairing. Go to your iPad's Bluetooth settings, forget the Slim Combo entry, then hold the keyboard's power button until the status LED flashes to enter pairing mode. Re-pair from scratch and the connection will stabilise at full signal strength.
Slim Combo keyboard unresponsive even after charging the new battery
If the keyboard stays dark after a full charge cycle, the BMS may be in deep-discharge lockout from the depleted original cell — a state that doesn't always clear on the first charge attempt. Connect the case to a 5V/1A USB-C source and leave it for 90 minutes before pressing the power button. The BMS requires the cell to reach approximately 3.0V before it will release the lockout and allow normal operation. If the LED still doesn't respond, disconnect and reconnect the charging cable to trigger a fresh BMS initialisation cycle.