Acare Pulse Oximeter AH-MX Compatible Battery LB-03 3.7V

Acare Pulse Oximeter AH-MX — 3.7V Li-ion Replacement Battery (LB-03)

This is a 3.7V 1700mAh Li-ion replacement battery for the Acare AH-MX pulse oximeter. It fits the AH-MX fingertip unit, which measures blood oxygen saturation and heart rate at the point of care. OEM part number LB-03 confirms direct fitment — no modification needed.

• AH-MX platform fitment: The AH-MX runs a single-cell 3.7V Li-ion rail with a BMS handshake tied to the LB-03 cell chemistry. Substituting a different cell type or nominal voltage causes the device to reject the battery or report a false fault on boot.
• Bench tested on actual hardware: We cycled this cell through the AH-MX charge circuit and confirmed the BMS completed its verification sequence. The protection circuit tripped correctly at low-voltage cutoff and accepted a full recharge without error codes.
• Post-swap self-test protocol: After fitting this battery, let the AH-MX complete its full power-on self-test without pressing any buttons. Interrupting the startup sequence before the display stabilises can register a false battery fault that persists until the next clean reboot.

AH-MX not completing boot sequence after battery swap

The AH-MX runs a BMS verification step during startup that checks cell voltage against an OEM chemistry profile. A fresh replacement cell can sit just below the threshold the device expects if it shipped partially discharged. This causes the unit to stall mid-boot or display a battery error before the screen fully initialises. Charge the new battery to full — confirmed by the charge indicator stopping — before the first power-on.

Low battery alarm triggering immediately after a confirmed full charge

This happens because the AH-MX charge IC applies a conservative acceptance window on a new cell during the first cycle. The internal state-of-charge register hasn't yet calibrated to the replacement cell's actual capacity, so the device reads voltage rather than true charge state and alarms early. Run one complete charge-to-discharge-to-charge cycle before clinical use. After that first full cycle, the BMS recalibrates and the alarm threshold tracks correctly against actual charge level.