Tianbao 92600 Survey Battery 7.4V 2000mAh Li-ion Replacement

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

This is a 7.4V 2000mAh (14.8Wh) lithium-ion replacement battery for Tianbao handheld survey instruments and field diagnostic tools. It replaces OEM part numbers 92600, 92670, and MA1805A. Physical dimensions are 70.60 × 38.60 × 20.54mm — verify these against your original pack before ordering.

• OEM part number cross-reference: Part numbers 92600, 92670, and MA1805A share the same 7.4V cell configuration, connector pinout, and BMS handshake protocol — all three are interchangeable in instruments that originally shipped with any one of these packs.
• Bench tested on actual hardware: We cycled this pack under sustained sensor load and monitored BMS behaviour through probe initialisation spikes. The BMS held without nuisance cutoff, and cell balance stayed within 20mV across the discharge curve.
• First-use calibration step: After installing this battery, run a full calibration cycle through the instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings during your first measurement session in the field.

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

Lithium-ion cells self-discharge at roughly 2–3% per month. A Tianbao pack left unused for six months or more can drop below the BMS re-initialisation threshold — typically around 2.5V per cell. When this happens, the BMS enters sleep mode and blocks charge input entirely. Standard charger behaviour in this state is no LED activity and no current draw, which looks identical to a dead charger or a dead port. To recover the pack, apply a brief low-current pre-charge pulse using a capable bench charger set to Li-ion recovery mode, then transition to normal CC/CV at 7.4V. Most packs recover fully once cell voltage clears 3.0V per cell.

Instrument powers on but shuts down during USB data transfer to PC

USB data transfer adds a secondary current draw on top of the active sensor load. In survey instruments, this combined draw can push instantaneous current high enough to trigger the BMS undervoltage cutoff — especially when cell capacity has partially degraded. The shutdown happens because the BMS sees a voltage sag that crosses its protection threshold, not because the pack is empty. Charge the battery to full before initiating any transfer session, and check that the USB cable is rated for data — cheap charge-only cables can cause handshake retries that spike current draw unpredictably.