Drummond Scientific Pipet-Aid XL 3.6V Replacement Battery

Drummond Scientific Portable Pipet-Aid XL — 3.6V Ni-MH Replacement Battery (4-000-036)

This 3.6V 700mAh Ni-MH cell replaces OEM part 4-000-036 in the Drummond Scientific Portable Pipet-Aid line. It fits the Portable Pipet-Aid XL, XP2, PK, and related models that share this battery form factor. Physical dimensions are 44.80 x 25.10 x 18.00mm — confirm fitment before installation.

• Pipet-Aid XL, XP2, PK platform: These models share the same 3.6V Ni-MH battery bay and connector pinout. The BMS in each device reads cell voltage at startup to verify chemistry match — a cell outside the expected voltage window at power-on will trigger a fault flag regardless of actual charge state.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS accepted the cell without a chemistry fault, and the charge circuit completed a full charge cycle to termination without hitting delta-V cutoff prematurely.
• Post-swap power-on sequence: After installing this cell, let the device complete its full power-on self-test without interruption. The Pipet-Aid BMS runs a voltage verification pass at boot — cutting power mid-sequence leaves a false battery fault latched in firmware that persists until the next clean reboot.

Why the Pipet-Aid XL reports low battery immediately after a confirmed full charge

The Pipet-Aid charge IC uses delta-V detection to determine end-of-charge, but it also applies a minimum voltage threshold during the BMS self-test at startup. A new Ni-MH cell that has not completed at least one full charge-discharge cycle will sit at a resting voltage slightly below the OEM cell's conditioned baseline. The BMS reads this as a marginal or low cell and raises a battery warning even though the cell is fully charged. Running one complete charge-discharge cycle conditions the cell voltage profile to match what the firmware expects. After that cycle, the low battery flag clears and does not return.

Pipet-Aid won't power on after the replacement cell sat in storage

Ni-MH cells self-discharge in storage at roughly 1–3% per day depending on temperature. A cell stored for several weeks can drop below 3.0V — the point at which the Pipet-Aid BMS refuses to initiate a charge cycle, treating the cell as damaged rather than depleted. Place the cell on a standalone Ni-MH charger capable of a recovery or trickle charge at 50–70mA to bring voltage above 3.2V first. Once above that threshold, reinstall the cell and the device charge circuit will resume normal operation.