Casio 2500 Cordless Phone Replacement Battery 3.6V 700mAh

Casio 2500 / 2600 Series — 3.6V Ni-MH Replacement Battery

This 3.6V, 700mAh Ni-MH battery replaces the factory pack in Casio cordless handsets including the 2500, 2600, T-2600, and T2600 series. It physically matches the original cell dimensions at 45.90 x 31.20 x 10.70mm, so it seats correctly in the handset battery compartment. When the original pack can no longer hold charge through a call, this is the direct swap.

• 2500 and 2600 series compatibility: These Casio handset models share the same 3.6V single-cell NiMH battery bay, connector orientation, and contact spacing. One pack covers the full model range listed.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a NiMH-compatible tester. The cell accepted charge cleanly and the voltage held stable through the discharge curve without premature cutoff.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in the base station and leave it for a full 16 hours before the first call. NiMH cells shipped from storage are partially discharged — a slow initial charge lets the pack reach rated 700mAh capacity. Skipping this step is the most common reason a new battery underperforms from day one.

Range drop on Casio 2500 and 2600 handsets after a battery swap

DECT handsets draw a sharp burst of current every time the RF transmitter fires. A NiMH cell that hasn't been fully conditioned has higher internal resistance, and that resistance causes the terminal voltage to sag under transmit load. When the voltage sags below the handset's transmit threshold, the radio reduces output power automatically. After three to five full charge and discharge cycles, internal resistance drops and the voltage holds steady under RF load — range returns to normal.

Base station shows no charge or error light with new battery installed

NiMH batteries in storage drift down to low resting voltages — sometimes below 3.0V. Some Casio base stations check the incoming pack voltage before starting the charge cycle, and a cell below that threshold triggers an error state rather than initiating a charge. Remove the handset, wait 30 seconds, and reseat it firmly so the contacts reset. If the error persists, verify the handset contacts are clean and the pack is sitting flush — a partial connection reads as a bad voltage to the base.