About this replacement
Hioki PW3198 / MR8875 Series — 7.2V Ni-MH Replacement Battery (Z1003)
This is a 7.2V 3600mAh Ni-MH battery pack replacing the Hioki Z1003. It fits the PW3198 three-phase power quality analyzer and the MR8875, MR8875-30, and PQ3100 data recorders. If your current pack no longer holds a charge through a full measurement session, this is the direct replacement.
- PW3198 and MR8875 platform compatibility: These instruments share the same Z1003 battery bay format, connector pinout, and 7.2V supply rail. The PW3198 routes battery voltage through its internal DC-DC stage to power the clamp sensor inputs and display simultaneously — the pack must deliver stable current under that combined load without voltage sag triggering the low-battery interrupt.
- Bench tested on actual hardware: We cycled this pack through simulated PW3198 load conditions — display active, voltage inputs live, current sensor channels powered. The BMS held within the instrument's operating voltage window across repeated draw cycles with no premature cutoff.
- Post-install calibration on the PW3198: After fitting this pack, run a full calibration cycle through the PW3198 instrument menu before field deployment. The instrument maps battery state during calibration, and skipping this step causes premature low-battery warnings during your first measurement session even with a fully charged pack.
PW3198 shutting down mid-measurement with clamp sensors connected
The PW3198 powers its current clamp inputs from the same battery rail as the processor and display. When all four clamp channels initialise at startup, the combined inrush current briefly spikes the draw above steady-state levels. A degraded or deeply discharged pack sags below the instrument's cutoff threshold at that moment, triggering an immediate shutdown. This is not a firmware fault — it is a voltage-supply failure under peak draw. Fit a fully charged replacement pack and confirm the terminal voltage reads at least 7.2V before powering on with all clamps attached.
Pack will not charge after the instrument sat unused in a carry case for months
Ni-MH cells self-discharge during storage, and if the pack drops below approximately 1.0V per cell (6.0V total), the PW3198 charger circuit will not initiate a charge cycle — it treats the pack as a fault condition. The battery management circuit enters a protection state and the instrument shows no charge activity. To recover the pack, apply a low-rate trickle charge externally at around 100mA until the terminal voltage climbs above 6.0V, then reinsert it into the instrument and charge normally. If the pack does not respond within 30 minutes of trickle charge, the cells have degraded past recovery and the pack needs replacing.