Bombas Infusion 11.1V Replacement Battery INR18650-3S1P

Bombas Infusion Pump — 11.1V Li-ion Replacement Battery (INR18650-3S1P)

This is an 11.1V, 2600mAh Li-ion replacement battery for the Bombas infusion pump. It uses an INR18650-3S1P cell configuration — three 18650 cells in series — matching the original voltage rail. Capacity figures are sourced from product data: 2600mAh, 28.86Wh.

• Infusion pump voltage rail: Infusion pumps regulate drug delivery against a tightly controlled voltage window. A 3S Li-ion pack holds nominal 11.1V across the full discharge curve, keeping the pump's microcontroller and motor driver within spec. A mismatched cell count shifts that curve and triggers premature low-battery shutoffs mid-infusion.
• Bench tested on actual hardware: We ran this pack through charge-discharge cycles on a cell tester before listing. The BMS balanced all three cells within 20mV at top-of-charge and held cutoff at 9.0V under a steady resistive load — consistent with OEM protection thresholds on medical-grade Li-ion packs.
• Post-swap self-test protocol: After installing this battery, allow the infusion pump to complete its full power-on self-test without interruption. The device BMS runs a verification sequence at startup. Cutting power during this window logs a battery fault that persists until the next clean reboot — even if the battery itself is fine.

Why the Bombas infusion pump alarms low battery on a freshly charged replacement

The pump's charge IC applies a conservative acceptance threshold calibrated to a conditioned OEM cell. A new replacement cell that has never cycled presents a slightly different impedance signature, which the device reads as below the safe-use threshold even at full charge. One complete charge-discharge cycle normalises the cell's internal resistance. After that cycle, the alarm clears and the state-of-charge display tracks accurately.

Infusion pump not completing boot sequence after cell sat in storage

Li-ion cells self-discharge during storage. If the pack voltage drops below the BMS deep-discharge recovery threshold — typically around 9.0V for a 3S pack — the protection circuit locks out and the pump cannot draw enough current to boot. Connect the pump to mains power and leave it on charge for at least 30 minutes before attempting to power on. This allows the charge IC to trickle current into the cells past the recovery threshold before switching to standard CC/CV charging.