Micro Medical MicroLab 3300 Replacement Battery 7.2V 1200mAh

Micro Medical MicroLab 3300 Spirometer — 7.2V Ni-MH Replacement Battery (MLA4303)

This 7.2V, 1200mAh Ni-MH battery replaces the OEM pack in the Micro Medical MicroLab 3300 Spirometer and MicroLab 3300 pulmonary function tester. It matches the original voltage rail and connector format used in these portable lung function testing units. Capacity is 1200mAh (8.64Wh), sourced directly from the product specification.

• MicroLab 3300 platform fit: The MicroLab 3300 Spirometer and MicroLab 3300 pulmonary function tester share the same battery bay dimensions and 7.2V BMS handshake. Both accept this pack under OEM part numbers MLA4303 and ML2000. No modification is required to the battery compartment.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on clinical-grade Ni-MH test equipment. The BMS accepted the pack without fault codes on the first cycle, and capacity output tracked within tolerance of the rated 1200mAh after the second full cycle.
• Post-installation self-test protocol: After fitting this battery, allow the MicroLab 3300 to complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during this window triggers a persistent battery fault that will not clear until the next clean reboot.

Why the MicroLab 3300 reports low battery immediately after a confirmed full charge

The MicroLab 3300 charge IC compares cell voltage against thresholds calibrated to an aged OEM cell chemistry profile. A fresh Ni-MH cell has a slightly different voltage curve during the first few cycles, so the BMS can flag a low-battery warning even when the pack is fully charged. This is not a fault with the replacement cell — it is the charge controller applying a conservative threshold before it has profiled the new pack. Run one complete charge-discharge-recharge cycle and the device will recalibrate its reading. After that cycle, the battery indicator should reflect actual charge state accurately.

MicroLab 3300 shuts off mid-test during the first week of use

New Ni-MH cells draw more internal resistance during the first 5–10 cycles, which causes brief voltage sag under the load spike of an active spirometry test. If the sag crosses the BMS undervoltage cutoff, the device shuts down to protect the circuit — even if the pack shows adequate charge before the test begins. This behaviour typically resolves after the cells condition through several full cycles. If shutdowns persist beyond 10 cycles, check resting cell voltage with a multimeter — a healthy pack at full charge should read at or above 8.4V across the terminals.