About this replacement
Sonel INDEX CAT — 9.6V Ni-MH Replacement Battery (WAAKU02 / AKU-02)
This is a 9.6V 2000mAh Ni-MH replacement battery for the Sonel INDEX CAT multimeter (WAAKU02 / AKU-02). It also fits the MIC-1000 and MIC-2500 insulation resistance testers. Same voltage, same connector, same form factor as the original pack.
- INDEX CAT, MIC-1000 and MIC-2500 compatibility: These instruments share the same 9.6V Ni-MH battery platform, connector pinout, and BMS handshake protocol. One pack covers all three models without modification.
- Bench tested on actual hardware: We cycled this pack under simulated probe initialisation loads — the current spike at probe power-up is the most common BMS trip point. The pack held voltage without triggering a cutoff across repeated initialisation events.
- First-use calibration on the INDEX CAT: After installing this pack, run a full calibration cycle through the instrument menu before taking it into the field. The INDEX CAT maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session.
BMS lockout after the INDEX CAT sat unused in a carry case for months
Ni-MH cells self-discharge over time. If the pack drops below approximately 8.5V during extended storage, the BMS enters a protective sleep state and the instrument will not power on — even connected to a charger. The recovery method is a slow trickle charge at 100–200mA for 30 to 60 minutes to bring cell voltage back above the BMS wake threshold. Once the pack recovers to around 9.0V, normal charging resumes and the instrument powers on.
Readings drifting or logging session resetting mid-test
Sustained sensor load during a logging session draws more current than a single spot measurement. If the battery is partially discharged, this load causes a voltage dropout below the instrument's operating floor, triggering a mid-session reset. This is not a firmware fault — it is a cell capacity issue. Charge the pack fully before any extended logging session and confirm the instrument shows a full charge indicator before starting.