Baxter Healthcare Sigma Spectrum 7.4V Replacement Battery 35724

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

This 7.4V, 1800mAh lithium-ion battery is a direct replacement for the Baxter Healthcare Sigma Spectrum infusion pump. It fits the Sigma Spectrum platform including models 35083, 35162, and 35700. Voltage and capacity match the OEM specification — no modifications needed for installation.

• Sigma Spectrum platform compatibility: The 35083, 35162, 35700, and related Sigma Spectrum models share the same 7.4V battery bay, connector pinout, and BMS handshake protocol. A single replacement cell covers the full platform without adapter or firmware change.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on Sigma Spectrum hardware. The BMS completed its handshake, accepted the charge curve without rejection, and the pump cleared self-test without triggering a battery fault code.
• Post-swap self-test protocol: After installing this battery, do not interrupt the pump's power-on self-test. The Sigma Spectrum runs a BMS verification sequence at every startup. Powering off mid-sequence causes the device to log a false battery fault that persists until the next complete reboot cycle.

Why the Sigma Spectrum charges to 100% but still alarms low battery

The Sigma Spectrum's charge IC applies a conservative acceptance threshold when it first encounters a new cell. Until the BMS completes a full charge-discharge learn cycle, the pump may read available capacity as below the alarm threshold even after a confirmed full charge. This is a calibration gap — not a fault with the cell. Run one complete charge-to-discharge cycle before placing the pump into clinical rotation. After that cycle, the alarm clears and the battery indicator reports accurately.

Pump fails to power on after battery sat in storage

Lithium-ion cells self-discharge during storage. If this battery sat long enough to drop below approximately 2.5V per cell (5.0V pack total), the BMS enters a protection lockout and blocks current output entirely. The pump will not power on — not because the cell is dead, but because the BMS is preventing an unsafe recovery draw. Connect the pump to mains power first and allow the charger to trickle the pack back above the BMS recovery threshold before attempting to boot on battery alone. Once the pack reaches approximately 6.0V, the BMS releases the lockout and normal charging resumes.