KIR 4040 Cordless Phone Compatible Battery 3.6V 700mAh Ni-MH

KIR 4040 / T-PLUS2 / 3020 / 3040 Series — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 700mAh Ni-MH replacement battery for KIR cordless phone handsets. It fits the 4040, T-PLUS2, 3020, and 3040 models, along with six additional handsets in the same family. It restores power to the handset so it can hold a charge and operate wirelessly from the base station.

• 4040 and T-PLUS2 series compatibility: These models share a common 3.6V three-cell Ni-MH pack format with matched connector pinout and physical dimensions of 45.00 × 31.10 × 10.50mm. The base station charging circuit targets the same voltage profile across all listed handsets.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the base station cradle and confirmed the charging circuit accepted the pack without error on the third cycle, with cell voltage rising consistently across all three cells.
• First-charge protocol for Ni-MH handsets: After installing, seat the handset in the base for a full 16-hour charge before first use. Ni-MH cordless phone packs arrive in a partially discharged state and need a slow first charge to reach rated capacity — skipping this step leads to shortened talk time from the start.

Base station showing no charge or flashing error light on a new Ni-MH pack

KIR base stations use a delta-V detection circuit to confirm a Ni-MH pack is accepting charge. If the pack arrives deeply discharged from storage, its resting voltage can sit below the threshold the base expects before starting a charge cycle. The base interprets this as a fault and displays an error or refuses to charge. To recover, hold the handset in the cradle for 10–15 minutes — most base stations will eventually trickle-charge the pack until it crosses the 3.2V acceptance threshold, after which normal charging resumes.

Talk time shorter than original battery for the first few uses

Ni-MH cells do not deliver full rated capacity on the first cycle — they need three to five full charge-discharge cycles to reach 700mAh. This is a chemistry characteristic, not a defect. Each full cycle allows the electrolyte to stabilise across all three cells, gradually increasing available capacity. Run the handset until it signals low battery, return it to the base for a full charge, and repeat this at least three times before judging talk time against the rated spec.