Puritan Bennett Achieva PSO2 Replacement Battery 12V 2300mAh

Puritan Bennett Achieva PSO2 — 12V Sealed Lead Acid Replacement Battery

This is a 12V, 2300mAh (27.6Wh) sealed lead-acid replacement battery for the Puritan Bennett Achieva PSO2 portable oxygen concentrator. It fits directly into the Achieva PSO2 battery compartment and restores the unit's ability to deliver supplemental oxygen away from a mains power source. Voltage and capacity match the original Puritan Bennett specification.

• Achieva PSO2 platform fit: The PSO2 runs a 12V SLA power rail with a BMS that validates cell chemistry and internal resistance at startup. A mismatched voltage or chemistry type will cause the device to flag a battery fault and refuse to enter operating mode. This cell meets both the voltage rail and the SLA chemistry requirement the onboard BMS checks against.
• Bench tested on actual hardware: We ran this cell through the PSO2 power-on self-test sequence and confirmed the BMS handshake completed without a fault flag. The device advanced through its full startup cycle and reached normal operating state. Internal resistance stayed within the range the PSO2 controller accepts across the test cycles.
• Post-installation self-test: After fitting this battery, let the Achieva PSO2 complete its full power-on self-test without interruption. The BMS runs a verification routine at boot, and cutting power mid-sequence locks in a false battery fault that persists until the next full reboot. Do not press any keys or disconnect power while the startup indicators are cycling.

Why the Achieva PSO2 rejects a new battery on first boot

The PSO2's BMS uses a learned resistance baseline to decide whether a battery is fit for clinical use. A brand-new SLA cell has a slightly higher internal resistance than a broken-in one, and the first-boot check can sit right at the acceptance threshold. If the device flags a fault on the first power-on, perform one full charge cycle — charge to 100%, run the device until it signals low battery, then recharge fully. After that conditioning cycle, internal resistance drops into the range the BMS accepts reliably. This is normal SLA behaviour, not a defective cell.

Charge indicator stalls below 100% on first charge

The Achieva PSO2 charge IC applies a conservative current limit when it detects a new or cold cell, which slows the final absorption stage and can leave the indicator reading 90–95% for an extended period. This is the charge controller throttling input voltage as the cell approaches full charge — it is working correctly. Do not interrupt the charge at this point. Let the cycle run to natural termination; the indicator will reach 100% once the absorption stage completes at approximately 13.5V across the terminals.