Tianbao 92600 7.4V Survey Battery 2600mAh Li-ion

Tianbao 92600 / 92670 / MA1805A — 7.4V Li-ion Replacement Battery

This 7.4V, 2600mAh (19.24Wh) Li-ion battery replaces the Tianbao OEM packs 92600, 92670, and MA1805A. It fits Tianbao portable survey, diagnostic, and field measurement instruments that run on this voltage rail. Cell dimensions are 70.40 × 38.70 × 20.50mm — confirm your OEM part number before ordering.

• Multi-part-number coverage: The 92600, 92670, and MA1805A share the same 7.4V cell format, connector pinout, and BMS handshake protocol. One replacement pack covers all three variants without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the bench, monitoring BMS cutoff thresholds and cell balance. The protection circuit held stable across charge termination and low-voltage cutoff events — no false trips during the test runs.
• First-use calibration on survey instruments: After fitting this battery, run a full calibration cycle through the instrument menu before field deployment. The instrument maps battery state during calibration, and skipping this step causes premature low-battery warnings in the first measurement session.

BMS lockout after the instrument sat unused in a carry case for months

Li-ion cells self-discharge slowly during storage. If a Tianbao instrument sits unused long enough, the pack voltage drops below the BMS recovery threshold — typically around 2.5V per cell. At that point the BMS latches into deep-discharge protection and the instrument will not power on even when connected to a charger. The fix is to apply a slow, low-current charge via a compatible charger for 15–30 minutes to nudge cell voltage back above the recovery floor, then resume normal charging. Once cells recover above approximately 6.0V combined, the BMS re-initialises and normal charging resumes.

Readings resetting or dropping out mid-logging session

Sustained sensor load during a long logging session draws more current than the instrument draws at idle. If cell voltage sags under that load — particularly as the pack ages — the instrument's voltage rail dips momentarily, causing readings to reset or the logging session to abort. This is not a firmware fault. The root cause is voltage dropout under continuous sensor current draw. Fitting a fresh pack with full cell capacity restores the voltage margin; after installation, verify the pack reads above 8.0V at rest before starting a new logging session.