About this replacement
Cisco IP DECT 6800 / 6825 — 3.7V Li-ion Replacement Battery (RTR001F05)
This is a 3.7V, 1200mAh Li-ion replacement battery for the Cisco IP DECT 6800 and IP DECT 6825 wireless handsets, including the CP6825-3PC-K9. It uses OEM part number RTR001F05 and fits the same battery bay without modification. Capacity is rated at 4.44Wh.
- IP DECT 6800 and 6825 compatibility: Both handsets share the same battery bay dimensions, voltage rail, and connector pinout. The RTR001F05 slot fits all three model variants without adapter or modification.
- Bench tested on actual hardware: We ran this battery on the IP DECT 6825 handset. The BMS accepted charge from the base station immediately, with no error state triggered during the initial charge cycle. Cell voltage at full charge measured 4.19V.
- First charge after installation: Place the handset in the base cradle and leave it undisturbed for a full charge cycle before putting it back into rotation. Li-ion cells shipped in partial-charge storage states perform inconsistently until the BMS completes one full charge-to-cutoff cycle.
Talk time shorter than expected after battery swap
Li-ion cells arrive from storage at around 40–60% charge, and the BMS calibration data from the old cell does not transfer to the new one. The handset's charge indicator may show full before the cell has actually completed a proper charge cycle. Run two or three full charge-discharge cycles through normal use and the reported capacity will align with the 1200mAh rating. If talk time is still short after three cycles, check that the handset is fully seated in the base — a partial contact on the charging pins reduces charge current significantly.
Handset not pairing with base after battery replacement
Removing the battery from a DECT handset cuts power completely, and some Cisco IP DECT 6800 series units lose their base station pairing when the RAM clears. This is not a fault with the replacement battery. Re-pair the handset using the standard DECT registration procedure: hold the handset near the base, press the registration button on the base for three seconds, then follow the on-screen prompt on the handset. The handset should show the base extension within 60 seconds.