About this replacement
Algol ZP-500N — 4.8V Ni-MH Replacement Battery (GPHC083N04)
This is a 4.8V, 800mAh Ni-MH replacement battery for the Algol ZP-500N handheld surveying instrument. It matches the OEM part number GPHC083N04 and fits the original battery bay without modification. Voltage and cell count are identical to the factory pack.
- ZP-500N platform fit: The ZP-500N uses a 4-cell Ni-MH configuration at 4.8V nominal. The connector pinout and physical dimensions (46.76 × 41.52 × 11.76mm) match the OEM pack, so the instrument's power management circuit recognises the replacement without error flags.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge under a sustained sensor load. The BMS held voltage above the instrument's cutoff threshold throughout, and probe initialisation current spikes did not trip protection.
- First-use calibration on the ZP-500N: After installing, run a full calibration cycle through the instrument menu before field deployment. The ZP-500N maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session in the field.
ZP-500N shutting down during probe initialisation
When the ZP-500N powers up a probe module, it draws a short current spike as the sensor circuit initialises. An aged or partially discharged Ni-MH pack can't sustain voltage through that spike, and the instrument's undervoltage protection trips before a reading is taken. This replacement pack uses fresh cells with lower internal resistance, which keeps the voltage rail stable through the initialisation surge. If shutdowns persist after fitting the new pack, charge to full before the next session — Ni-MH cells perform best above 4.6V under load.
Pack won't charge after the ZP-500N sat unused for months
Ni-MH cells self-discharge over storage, and a pack left in the instrument for several months can drop below the charger's minimum detection voltage. When this happens, the charger sees too low a voltage to begin a charge cycle and does nothing. To recover, connect the instrument to the charger and leave it for 30–60 minutes — some chargers apply a trickle current first that brings the cell voltage back above the charge-enable threshold. If the charge indicator still doesn't activate after that window, the cells have dropped below 1.0V per cell and the pack needs replacement rather than recovery.