Kenwood PB-43N TH-K2AT Replacement Battery 7.2V 1800mAh

Kenwood TH-K2AT / TH-K4AT Series — 7.2V Ni-MH Replacement Battery (PB-43N)

This is a 7.2V, 1800mAh Ni-MH replacement battery for the Kenwood TH-K2AT, TH-K4AT, TH-K2E, and TH-K2ET portable transceivers. It replaces OEM part numbers PB-43N, PB-43H, KNB-43, and PB-43. The battery slots into the same bay as the original pack with no modifications required.

• TH-K2 and TH-K4 platform fit: These models share the same battery bay dimensions, contact layout, and 7.2V rail. The BMS handshake protocol is consistent across the series, so the same pack services all four listed variants without adaptation.
• Bench tested on actual hardware: We cycled this pack in a TH-K2AT dock and monitored BMS behaviour through full charge and a sustained PTT load test. The BMS held the voltage rail steady under transmit current draw and triggered no spurious cutoffs.
• First-insertion contact cycle on the Kenwood dock: If the charger dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Kenwood dock requires a clean contact cycle to accept the new BMS handshake before charging begins.

Why the TH-K2AT cuts out mid-transmission on a new battery

A new Ni-MH cell ships at storage voltage — typically around 6.8V to 7.0V, below the pack's nominal 7.2V. When PTT is pressed, transmit current spikes sharply, and a cell at storage voltage can dip far enough to trigger the BMS overcurrent protection. The radio goes silent not because the pack is faulty, but because the BMS is doing its job on an undercharged cell. Put the pack through one full charge cycle on the Kenwood dock before the first use, and the cutout behaviour stops.

Bar indicator showing one fewer bar than expected after fitting this pack

The TH-K2AT uses a voltage-threshold bar indicator — each bar maps to a specific voltage band. A new Ni-MH pack at storage voltage sits in the lower threshold band, so the display reads one bar short even though the cell is not depleted. This is not a capacity defect. After a full charge cycle the resting voltage rises above the next threshold, and the indicator moves to the correct bar. Charge fully on the Kenwood dock and recheck the display before drawing any conclusions about the pack.