Panasonic HHR-P401 Cordless Phone Replacement Battery 3.6V

Panasonic KX-TG2397 / KX-TG2400 Series — 3.6V Ni-MH Replacement Battery (HHR-P401)

This is a 3.6V, 1200mAh Ni-MH rechargeable battery for Panasonic cordless phone handsets, including the KX-TG2397, KX-TG2400, KX-TG2400B, and KX-TG2405 series. It replaces OEM part numbers HHR-P401 and HHR-P401A directly. The battery restores handset function when the original cell can no longer hold a usable charge.

• KX-TG2397 and KX-TG2400 series compatibility: These models share the same 3.6V three-cell NiMH pack format, identical connector pinout, and physical footprint — 54.46 x 32.07 x 11.22mm — so one battery works across the entire KX-TG2400 handset family without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the KX-TG2400 platform and confirmed the base station accepts the charge state correctly, with no error light triggered during the initial acceptance phase.
• First-charge protocol for NiMH cordless handsets: After installing, seat the handset in the base and leave it for a full 16 hours before first use. NiMH cells ship partially discharged; the slow first charge allows all three cells to reach balanced capacity and prevents early capacity fade.

Talk time shorter than the original battery after replacement

NiMH cells do not deliver rated capacity on the first cycle — or even the second or third. The chemistry requires three to five full charge-discharge cycles before the cells reach their rated 1200mAh. If talk time feels short straight out of the box, that is expected behaviour, not a fault. Run the handset to low charge and return it to the base each time; capacity improves measurably by cycle four or five.

Base station shows no charge or error light after battery swap

NiMH packs sitting in warehouse storage self-discharge over time and can drop to a voltage level that some Panasonic base stations read as a fault rather than a depleted cell. The base station's charge acceptance circuit expects to see a resting voltage above roughly 3.0V before it begins a normal charge cycle. If the indicator light stays red or shows an error, remove the handset, wait 30 seconds, and reseat it firmly — this resets the charge handshake. If the issue persists, confirm the battery contacts on both the handset and the base are clean and making solid contact.