Fresenius Agilia 4+ Replacement Battery 7.4V 2600mAh

Fresenius Agilia 4+ / 6+ / 8+ / Link+ — 7.4V Li-ion Replacement Battery (Z178899)

This 7.4V 2600mAh (19.24Wh) lithium-ion battery replaces part numbers Z178899 and 179033-R2 in the Fresenius Agilia infusion pump series. It fits the Agilia 4+, 6+, 8+, and Link+ platforms, enabling portable operation between mains charging cycles. Voltage and cell dimensions match the original pack: 70.00 × 36.90 × 18.70mm.

• Agilia series compatibility: The 4+, 6+, 8+, and Link+ share the same 7.4V battery bay, connector pinout, and BMS communication protocol — one cell fits the full range without modification.
• Bench tested on actual hardware: We cycled this cell through full charge-discharge on the Agilia platform and confirmed the BMS handshake completes correctly, charge termination triggers at the expected threshold, and no false low-battery flags appear after the first full cycle.
• Power-on self-test — do not interrupt: After fitting this battery, let the Agilia complete its full startup self-test sequence without pressing any keys or connecting to mains mid-cycle. The BMS runs a verification routine at boot; interrupting it logs a battery fault that persists until the next clean reboot.

Why the Agilia alarms low battery immediately after a confirmed full charge

The Agilia's charge IC applies a conservative acceptance threshold calibrated to an aged OEM cell, not a fresh one. A new cell at full charge can present a slightly different internal resistance profile, which the BMS initially reads as below its pass threshold. This is not a fault with the cell — it resolves after one complete charge-discharge cycle, during which the BMS updates its reference baseline. Run the pump on battery to a normal low-battery cutoff, then charge fully before clinical use.

Agilia will not power on after the replacement battery sat in storage

Li-ion cells self-discharge at roughly 2–3% per month in storage. If the cell voltage drops below the Agilia's BMS recovery threshold — typically around 6.0V for a 7.4V nominal pack — the BMS locks out to prevent damage and the pump will not boot. Connect to mains immediately and leave on charge for at least four hours before attempting to power on. If the pump still does not respond after that charge period, check that the connector is fully seated and the charge LED has activated — a partial connection can prevent the charge circuit from engaging.