About this replacement
Kenwood TK-25A / TK-26A Series — 7.2V Ni-MH Replacement Battery (PB-13)
This is a 7.2V 1300mAh Ni-MH replacement battery for the Kenwood TK-25A, TK-26A, TK-27A, TK-28A, and over 26 additional TK-series handheld radios. It replaces OEM part numbers PB-13, PB-13H, PB-14, PB-15, PB-17, and PB-18. The pack slots directly into the original battery bay and uses the same contact layout as the factory unit.
- TK-series platform fit: These TK-series portables share a common 7.2V Ni-MH battery bay, contact pin arrangement, and BMS handshake protocol across the 25A through 28A range. That shared architecture is why one pack covers the full model spread — the voltage rail and connector spec did not change between those variants.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge on a TK-series radio under simulated PTT load. The BMS handled the transmit current spike without tripping, and the voltage recovery between transmissions held within expected Ni-MH flatline range.
- First insertion into the charger dock: If the dock LED flashes fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. Kenwood TK-series chargers require a clean contact cycle to complete the BMS handshake before the charge cycle begins.
Why the TK-25A cuts out mid-transmission on a freshly inserted battery
Ni-MH cells ship at storage voltage — typically around 6.0–6.5V — not at full charge. When you press PTT, the radio draws a sharp transmit current spike. If the resting cell voltage is already low, that spike pulls the pack below the BMS cutoff threshold and the radio drops audio or cuts transmission entirely. This is not a faulty battery. Run one full charge cycle in the dock before putting the radio into service and the cutout behaviour stops.
Bar indicator showing one fewer bar than expected after a full charge
Kenwood TK-series radios read pack voltage against fixed thresholds to light each bar segment — there is no fuel gauge chip involved. A new Ni-MH cell that has not yet been fully conditioned sits slightly below its rated terminal voltage even after a first charge, which pushes the reading one bar low. Run two to three full charge-discharge cycles and the resting voltage climbs to match the threshold the radio expects. After conditioning, the bar display aligns correctly at a rested pack voltage of approximately 7.2V.