About this replacement
CONTEC HMS7500 — 7.4V Li-ion Replacement Battery (2.3.02.00200)
This 7.4V 6800mAh Li-ion battery replaces OEM part 2.3.02.00200 in the CONTEC HMS7500 pulse oximeter. The HMS7500 is a portable vital signs monitor used in clinical and home care settings to measure blood oxygen saturation and pulse rate. When the original cell degrades, this replacement restores full operating capacity at the correct voltage and connector configuration.
- HMS7500 fit: The HMS7500 uses a dedicated 7.4V Li-ion pack with a proprietary BMS handshake. This battery matches the OEM cell voltage, connector pinout, and charge profile the device expects — the monitor will not boot correctly on a mismatched pack.
- Bench tested on actual hardware: We ran this cell through the HMS7500 charge cycle and verified BMS communication at startup. The self-test sequence completed without fault codes, and the charge IC accepted the cell without triggering an OEM-mismatch reject.
- Power-on self-test sequence: After fitting this battery, allow the HMS7500 to complete its full boot and self-test cycle without interruption. Cutting power during startup triggers a BMS fault flag that persists until the next clean reboot — it does not indicate a faulty cell.
HMS7500 low-battery alarm firing immediately after a confirmed full charge
The HMS7500 BMS is calibrated to OEM cell chemistry and applies a conservative capacity threshold on first use. A new replacement cell has not yet completed a full charge-discharge learn cycle, so the BMS can misread state-of-charge and trigger the alarm even at a full 8.4V terminal voltage. This is not a fault with the cell — it is the BMS defaulting to a protective floor until the pack is profiled. Run one complete charge-discharge cycle, charge back to 8.4V, and the alarm threshold recalibrates correctly.
Device will not power on after the replacement battery sat in storage
Li-ion cells self-discharge during storage at roughly 2–3% per month. If this battery arrived or was stored for an extended period, terminal voltage may have dropped below the HMS7500's BMS recovery threshold — typically around 6.0V for a 7.4V nominal pack. Below that floor, the BMS locks out discharge to prevent cell damage, and the monitor shows no signs of life. Connect the device to its AC adapter and leave it on charge for at least two hours before attempting to power on — the charger's pre-charge stage recovers cells above 5.5V.