Micronix MB-300 MSA338 Replacement Battery 4.8V 4000mAh

Micronix MSA338 / MSA358 — 4.8V Ni-MH Replacement Battery (MB-300)

This is a 4.8V, 4000mAh Ni-MH battery for the Micronix MSA338 and MSA358 survey and measurement instruments. It replaces OEM part number MB-300 directly. Rated at 19.2Wh, it matches the original cell count and voltage rail these instruments require.

• MSA338 and MSA358 compatibility: Both models share the same battery bay geometry, connector pinout, and 4.8V operating rail. The BMS handshake is identical across the two, so one replacement pack covers either unit without modification.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge runs on the MSA338 platform. The BMS handled sensor initialisation current spikes without tripping, and voltage held stable under sustained measurement loads.
• Pre-deployment calibration cycle: After fitting a new pack, run a full calibration cycle through the instrument menu before going into the field. The MSA338 maps battery state during that calibration pass — skipping it causes the low-battery indicator to trigger prematurely on your first measurement session.

MSA338 shutting down mid-measurement with no low-battery warning

The MSA338 draws a short current spike each time it powers a sensor or probe module. On a degraded or deeply discharged pack, that spike is enough to pull cell voltage below the BMS cutoff threshold momentarily — the instrument interprets this as a dead battery and shuts down. The display may not show a warning because the voltage drop happens faster than the indicator can update. A new pack with healthy internal resistance handles these spikes without the voltage sag that triggers cutoff.

Pack will not charge after the instrument sat unused for months

Ni-MH cells that sit at low voltage for an extended period can drop below the charger's detection threshold, causing the charger to reject the pack entirely. This is a BMS sleep state, not a dead battery. To recover, apply a slow trickle charge at 0.1C for 15–30 minutes to bring cell voltage above the 1.0V-per-cell recognition floor. Once the charger detects the pack, proceed with a normal charge cycle.