About this replacement
Fresenius Agilia Series — 7.4V Li-ion Replacement Battery (Z178899)
This 7.4V, 3350mAh Li-ion battery replaces OEM part Z178899 / 179033-R2 in the Fresenius Agilia infusion pump range. It fits the Agilia 4+, 6+, 8+, and Agilia Link+. Capacity matches the original at 3350mAh (24.79Wh).
- Agilia platform fit: The 4+, 6+, 8+, and Link+ all share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell revision covers the full Agilia range without modification.
- Bench tested on actual hardware: We cycled this cell through the Agilia pump's charge-and-verify sequence. The BMS accepted the cell on first recognition, completed its state-of-charge calibration, and held voltage within spec under simulated pump load.
- Post-installation self-test requirement: After fitting, allow the pump to complete its full power-on self-test cycle without interruption. Medical-grade BMS firmware runs a capacity verification at startup — cutting power mid-sequence triggers a false battery fault that persists until the next full reboot.
Why the Agilia pump shows a battery fault after a confirmed full charge
The Agilia's BMS uses a stored chemistry profile calibrated to the original cell's internal resistance curve. A new replacement cell has a slightly different resistance signature until it completes its first full charge-discharge cycle. During this break-in period, the BMS may interpret the mismatch as a fault condition even when the cell is fully charged. Run one complete charge and discharge cycle outside clinical use before placing the pump back into service — the BMS recalibrates its threshold on the next full cycle and the fault clears.
Charge indicator stalling below 100% on first charge
On the first charge, the Agilia's charge IC applies a conservative current ceiling to new cells — this is deliberate. The charge algorithm holds at a reduced topping rate while it measures the cell's acceptance characteristics, which makes the progress bar appear stalled between 85% and 95%. Do not disconnect and reconnect power to force a restart; this resets the algorithm and extends the total charge time further. Leave the pump on charge undisturbed and the cell will reach full charge — verify with a resting voltage of 8.2–8.4V before use.