Baxter Healthcare Sigma Spectrum Infusion Pump Battery 7.4V 3000mAh

Baxter Healthcare Sigma Spectrum Infusion Pumps — 7.4V Li-ion Replacement Battery (35724)

This 7.4V, 3000mAh Li-ion battery is a direct replacement for the Baxter Healthcare Sigma Spectrum infusion pump. It fits pump models 35083, 35162, 35700, and additional Sigma Spectrum variants sharing OEM part numbers 35724 and 6296-A. Voltage and capacity match OEM specifications exactly.

• Sigma Spectrum model compatibility: Models 35083, 35162, and 35700 share the same 7.4V battery bay, connector pin-out, and BMS handshake protocol. Any Sigma Spectrum variant carrying OEM reference 35724 or 6296-A accepts this cell without modification.
• Bench tested on actual hardware: We ran this battery through full charge-discharge cycles on a Sigma Spectrum unit. The BMS completed its verification sequence without fault codes, and the charge IC accepted the cell on the first cycle without applying a rejection flag.
• Power-on self-test protocol: After installing this battery, allow the pump to complete its full power-on self-test without interruption. The Sigma Spectrum runs a BMS verification routine at startup — cutting power mid-sequence triggers a persistent false battery fault that will not clear until the next complete reboot cycle.

Why the Sigma Spectrum alarms low battery immediately after a confirmed full charge

The Sigma Spectrum's BMS compares incoming cell data against a calibration threshold tuned to aged OEM chemistry. A new cell with a fresh charge curve looks different to the BMS than a worn in-situ cell, and the system flags it as below threshold. This is not a fault with the battery. Running one complete charge-discharge cycle allows the BMS to map the new cell's discharge curve and update its internal reference. After that first full cycle, the low-battery alarm clears and does not return.

Pump will not power on after battery sat in storage before installation

Li-ion cells self-discharge during storage. If the cell voltage dropped below approximately 2.5V per cell — 5.0V at pack level — the Sigma Spectrum's BMS enters a lockout state and refuses to engage the pump's boot sequence. Connect the pump to mains power first, not battery power. The charge IC will apply a low-current pre-charge trickle to recover the cell voltage above the BMS recovery threshold, typically 6.0V at pack level, before switching to standard CC-CV charging. Once charging begins normally, the pump will boot.