Bistos BT-740 Pulse Oximeter Compatible Battery 11.1V 4400mAh

Bistos BT-740 / BT-770 Pulse Oximeter — 11.1V Li-ion Replacement Battery (022-000021-00)

This 11.1V, 4400mAh Li-ion battery replaces OEM part 022-000021-00 in the Bistos BT-740 and BT-770 pulse oximeters. These are clinical-grade patient monitoring devices measuring blood oxygen saturation and pulse rate. The battery slots directly into the compartment used across both model variants.

• BT-740 and BT-770 compatibility: Both models share the same 11.1V battery rail, connector pinout, and BMS communication protocol, which is why a single cell fits both. The charge management circuit on either unit reads cell state the same way — no firmware difference between them affects battery handshake.
• Bench tested on actual hardware: We cycled this cell through charge and load on the BT-740 platform. The BMS completed its verification sequence without fault flags, and the protection circuit responded correctly to the oximeter's low-draw monitoring load profile.
• Post-swap self-test protocol: After installing this battery, let the BT-740 or BT-770 complete its full power-on self-test without interrupting it. The device runs BMS verification at startup — cutting power during that sequence plants a false battery fault that won't clear until the next full reboot.

Why the BT-740 alarms low battery immediately after a confirmed full charge

The BT-740's charge IC applies OEM chemistry thresholds when evaluating a new cell. On first charge, it sets a conservative upper voltage limit and the BMS flags the cell as not meeting its learned capacity baseline. This triggers a low-battery alarm even when the cell is fully charged. One complete charge-discharge cycle lets the BMS recalibrate its state-of-charge model to the new cell's actual capacity — the alarm clears after that cycle.

BT-770 will not power on after the battery sat in storage

Li-ion cells self-discharge during storage. If the cell voltage drops below approximately 2.5V per cell — around 7.5V for an 11.1V three-cell pack — the BMS enters deep-discharge lockout and blocks output. The device shows nothing on screen and does not respond to the power button. Connect the battery to a charger first, before reinserting it into the oximeter, and leave it on charge for at least 30 minutes to bring the cells above the BMS recovery threshold before attempting to power on.