About this replacement
Aastra DT690 Series — 3.7V Li-ion Replacement Battery (660190/1A)
This is a 3.7V, 930mAh Li-ion replacement battery for the Aastra DT690, DT692, and DH4-BAAA/2B cordless DECT handsets. It slots into the same battery compartment as the original 660190/1A pack. Capacity is rated at 3.44Wh, matching the original specification.
- DT690, DT692, and DH4-BAAA/2B fit: All three models share the same 3.7V single-cell Li-ion architecture, connector pinout, and BMS handshake protocol — which is why one battery covers the entire group.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the DT690 handset. The BMS accepted the charge from the base station without error and held voltage within the expected range across the full discharge curve.
- First-charge protocol for DECT handsets: After installing, seat the handset in the base and leave it for a full 16 hours before the first call. Li-ion cells shipped in partial-charge storage states need a complete slow charge cycle to register correctly with the handset's fuel gauge.
Talk time shorter than the original battery after replacement
A new Li-ion cell leaves the warehouse at around 40–60% charge. The DT690 handset reads state-of-charge from the BMS, so a partially charged pack will report a lower capacity than the cell actually holds. The fix is to complete two or three full charge-discharge cycles through the base station. After the third cycle, the handset's fuel gauge recalibrates and talk time will reflect the full 930mAh rating.
Handset loses DECT pairing when the battery is swapped
Removing the battery cuts all power to the DT690's volatile memory, which can erase the stored base station registration. This is not a fault with the new battery — it is a known behaviour in this DECT handset series. To restore pairing, press and hold the registration button on the base station, then follow the re-pairing sequence on the handset. The process takes under two minutes and restores full functionality at that point.