Caire Inc AirSep Freestyle 3 Compatible Battery 14.8V 3600mAh

Caire Inc AirSep Freestyle 3 — 14.8V Li-ion Replacement Battery (BT015-1)

This 14.8V, 3600mAh lithium-ion battery replaces OEM part numbers BT015-1 and BT018-1S in the AirSep Freestyle 3 and Freestyle 5 portable oxygen concentrators. It powers the concentrator during mobile use when patients need oxygen therapy away from a stationary oxygen source. Voltage and capacity match the original cell specifications for these units.

• Freestyle 3 and Freestyle 5 platform: Both models run the same 14.8V four-cell Li-ion architecture and share a common BMS handshake protocol, which is why BT015-1 and BT018-1S cross-reference across the platform. The connector pinout and BMS communication lines are identical between units.
• Bench tested on actual hardware: We cycled this cell through the Freestyle 3 charge-discharge sequence and confirmed the BMS completed capacity registration without triggering a fault code. Charge acceptance matched the OEM profile across the full voltage window from 12.0V to 16.8V.
• Power-on self-test protocol: After installing this battery, let the device complete its full startup self-test sequence without powering it off. Medical-grade concentrators run a BMS verification step at boot — interrupting it locks in a false battery fault that will not clear until the next complete power cycle from rest.

Why the Freestyle 3 alarms low battery with a freshly charged replacement installed

The Freestyle 3 BMS stores a learned capacity model from the previous cell. When a new cell arrives with a different internal resistance profile, the BMS reads the discharge curve as shallower than expected and flags it as low before the actual state of charge drops. This is a calibration issue, not a fault with the battery itself. One full charge-to-discharge cycle on the new cell resets the learned model and clears the alarm behaviour. Run that cycle before clinical use.

Freestyle 3 not completing boot sequence after battery swap

If the concentrator stalls mid-boot after fitting this battery, the cell voltage at rest is likely sitting below the BMS boot-admission threshold — typically around 12.5V — after storage. The BMS interprets sub-threshold voltage as an unsafe or depleted cell and halts the startup sequence as a protective measure. Connect the unit to mains power first and allow a 15-minute pre-charge before attempting to boot on battery alone. Once resting voltage climbs above 13.0V, the boot sequence completes normally.