Amada Miyachii MM-410A Compatible Battery 7.4V 2200mAh UR-250

Amada Miyachii MM-410A Series — 7.4V Li-ion Replacement Battery (UR-250)

This is a 7.4V 2200mAh Li-ion replacement battery for the Amada Miyachii MM-410A portable surveying and measurement instrument. It fits the MM-410A, MM-410A-00-00, and 2M1183 variants using OEM part number UR-250. The cell pack matches the original voltage rail and connector format for these field instruments.

• MM-410A, MM-410A-00-00, and 2M1183 compatibility: All three model designations use the same 7.4V two-cell Li-ion configuration and identical battery bay connector. The BMS handshake protocol is shared across the series, so one pack covers all three without any hardware modification.
• Bench tested on actual hardware: We ran this pack through power-on, sensor initialisation, and sustained measurement logging cycles. The BMS held its protection thresholds correctly during probe power-up current spikes and did not trigger false cutoffs under normal instrument load.
• Post-install calibration cycle: After fitting this pack, run a full calibration sequence through the MM-410A instrument menu before taking it into the field. The instrument maps battery state during that cycle — skipping it causes premature low-battery warnings during the first measurement session, even with a full charge.

BMS lockout after the MM-410A sat unused in a carry case for months

Li-ion cells self-discharge over storage. If the MM-410A sits unused long enough, cell voltage drops below the BMS recovery threshold — typically around 2.5V per cell. At that point the BMS enters a locked protection state and the instrument shows no sign of life even when placed on charge. The charger sees the pack as a fault condition and refuses to begin a charge cycle. To recover, apply a compatible charger that supports a low-voltage pre-charge or trickle mode, hold it on the pack for 15–20 minutes at reduced current until cell voltage climbs above 3.0V per cell, then charge normally.

Readings drifting or resetting mid-session during continuous data logging

Sustained sensor load on the MM-410A draws more current than standby or single-measurement use. If the cell's internal resistance has risen — common in aged packs — voltage sags under that continuous draw, crossing the instrument's low-voltage threshold briefly and causing a mid-session reset or reading dropout. The instrument may recover and continue, but logged data up to that point is lost or corrupted. Replace the pack if you see this pattern; a new cell at 2200mAh will maintain voltage above the instrument's operating floor under sustained load. Confirm the new pack is fully charged to 8.4V before a long logging session.