Aastra DT690 Replacement Battery 3.7V 900mAh Li-ion

Aastra DT690 / DT692 — 3.7V Li-ion Replacement Battery (660190/1A)

This is a 3.7V, 900mAh Li-ion replacement battery for the Aastra DT690 and DT692 DECT cordless handsets, and the DH4-BAAA/2B. It matches OEM part number 660190/1A and fits directly into the battery compartment of those handsets. If your DT690 is dropping calls due to low power or refusing to hold charge, this battery addresses the cause directly.

• DT690, DT692, and DH4-BAAA/2B compatibility: These three models share the same battery bay dimensions (51.75 × 35.90 × 7.26mm), the same 3.7V supply rail, and the same OEM part number. One battery fits all three without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a DT690 handset. The BMS accepted charge from the base station without triggering an error state, and voltage held stable under both active call load and standby draw.
• First charge on a DECT handset base: After fitting, seat the handset in its base and leave it for a full 16 hours before using it. Li-ion cells shipped in partial-charge storage states need a complete first charge to let the BMS calibrate the usable capacity range accurately.

Talk time shorter than the original battery after replacement

A new Li-ion cell calibrates its capacity window over the first few charge cycles. The BMS starts with a conservative estimate of usable charge and expands it as it learns the actual cell behaviour. On the DT690, this means the first two or three charges may feel noticeably shorter than expected. Complete full charge cycles — don't top up mid-day — and capacity will reach its rated 900mAh within three to five cycles.

Base station charge indicator not responding after battery swap

If the base shows no charge light after fitting a new battery, the cell voltage may be below the base station's acceptance threshold after shipping. Aastra base stations check for a minimum voltage before initiating the charge cycle. Connect the handset to the base and wait up to 10 minutes — a deeply discharged cell will trickle-charge up to the acceptance threshold before the indicator activates. If the light still doesn't come on, check that the handset contacts are clean and the handset is fully seated.