Sanyo CLT-4ER Cordless Phone Replacement Battery 3.6V 600mAh

Sanyo CLT-4ER / CLT-5ER / CLT-6ER Cordless Phone — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 600mAh Ni-MH replacement battery for Sanyo cordless phone handsets including the CLT-4ER, CLT-5ER, CLT-6ER, and 29519A series. It slots into the handset battery compartment and powers the DECT radio, display, and keypad. The original Sanyo pack uses the same voltage and cell format, so this replacement restores full handset function without any modification.

• CLT-series handset compatibility: The CLT-4ER, CLT-5ER, CLT-6ER, and 29519A share the same 3.6V three-cell Ni-MH pack format, physical footprint, and connector orientation. The base station charges via contact pins calibrated for Ni-MH voltage curves — this pack meets that profile directly.
• Bench tested on actual hardware: We cycled this pack on a CLT-series handset and confirmed the base station accepted the charge handshake without an error light. The BMS held steady through full charge and discharge without thermal cutoff or voltage drop at the contacts.
• First charge protocol for Ni-MH cordless handsets: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped in partial-discharge storage need a slow, complete initial charge to calibrate to rated capacity — skipping this results in shortened talk and standby performance for the first several cycles.

Base station showing no charge or error light after installing a new pack

Sanyo base stations check incoming voltage from the handset contacts before initiating a charge cycle. A Ni-MH pack that has sat in storage at low voltage can read below the base's acceptance threshold — typically around 3.0V — causing the charge indicator to stay off or flash an error. This is a voltage floor check, not a hardware fault. Place the handset in the base anyway and leave it undisturbed for several hours; most bases will begin trickle-charging once the pack voltage climbs past the threshold. If the error persists after 4 hours, check that the contact pins on both the handset and base are clean and making firm contact.

Range drops noticeably on the new battery compared to the old one

Reduced range after a battery swap is usually a voltage sag issue, not a radio fault. DECT handsets draw a higher current burst during transmission, and an unconditioned Ni-MH pack will sag in voltage under that RF load, causing the transmitter to reduce output power. This typically resolves after 3 to 5 full charge-discharge cycles, which allows the cells to reach their rated capacity. If range is still short after five cycles, measure the resting voltage of the pack after a full charge — it should read at or above 4.2V for a healthy 3-cell Ni-MH pack.