About this replacement
Drager Infinity M540 — 7.4V Li-ion Replacement Battery (MS29574)
This is a 7.4V, 3400mAh Li-ion battery for the Drager Infinity M540 portable patient monitor. It replaces OEM part numbers MS29574 and MS17465. The Infinity M540 is used in clinical and transport settings to continuously monitor heart rate, SpO2, and blood pressure when AC power is unavailable.
- Infinity M540 and M450 series fit: These monitors share the same battery bay geometry, connector pinout, and BMS handshake protocol across the M540, Infinity M540 Monitor, and Infinty monitor M450 variants — one cell services the full group.
- Bench tested on actual hardware: We cycled this battery through the M540's power-on sequence and monitored BMS communication. The cell passed charge authentication, held voltage within spec under simulated monitoring load, and did not trigger a battery fault flag at any point in testing.
- Post-swap power-on protocol: After installing this battery, allow the M540 to complete its full power-on self-test without interruption. The device runs a BMS verification step at startup — cutting power during this sequence logs a false battery fault that persists until the next clean reboot.
Drager Infinity M540 alarming low battery immediately after a confirmed full charge
The M540's charge IC applies a conservative acceptance threshold tuned to the OEM cell's internal resistance profile. A new replacement cell has a slightly different resistance signature on the first cycle, which the BMS interprets as insufficient charge state. This is not a fault with the cell — it clears after one full charge-discharge cycle. Run the battery down under normal monitoring load, then charge it completely before returning it to clinical rotation. After that first cycle, the alarm should no longer trigger at full charge.
Infinity M540 will not power on after battery sat unused in storage
Li-ion cells self-discharge during storage. If this battery arrived or was stored for an extended period, the cell voltage may have dropped below the M540's BMS recovery threshold — typically around 2.5V per cell, or 5.0V at pack level. The BMS locks out power-on to protect the cell from damage at deep discharge. Place the battery on the M540 charger and leave it connected for a minimum of two hours before attempting to power on. If the charge indicator does not respond after two hours, check the charger contacts and retry.