Kenwood PB-13 TK-25A Replacement Battery 7.2V 700mAh

Kenwood TK-25A / TK-28A Series — 7.2V Ni-MH Replacement Battery (PB-13)

This is a 7.2V, 700mAh Ni-MH replacement battery for the Kenwood TK-25A, TK-26A, TK-27A, and TK-28A handheld two-way radios, along with more than 26 additional compatible models. It replaces OEM part numbers PB-13, PB-13H, PB-14, PB-15, PB-17, and PB-18. Physical dimensions are 57.52 x 48.15 x 30.00mm — match these to your original pack before ordering.

• TK-25A through TK-28A platform compatibility: These four radio models share the same battery bay geometry, contact pitch, and 7.2V supply rail. One pack covers the entire line because the BMS handshake requirements are identical across the series — no firmware or connector differences to account for.
• Bench tested on actual hardware: We cycled this pack through full charge and transmit load on the TK-25A platform. The BMS held through repeated PTT bursts without tripping overcurrent cutoff, and charge acceptance on the drop-in dock completed without fault indication.
• First insertion into the charger dock: If the dock LED flashes fault on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly. The Kenwood dock requires a clean contact surface to complete the BMS handshake before it will begin the charge cycle.

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 for a 7.2V pack — not at full charge. When PTT is pressed, transmit current spikes sharply, and a cell sitting at storage voltage sags further under that load. If the radio's low-voltage cutoff threshold sits at 6.0V, that momentary sag can trip it mid-transmission. The fix is straightforward: charge the pack fully before the first transmit session. A full charge brings cell voltage up to the 8.4–8.5V range, giving adequate headroom above cutoff during TX bursts.

Bar indicator showing one fewer bar than expected after a full charge

The TK-series bar indicator reads voltage thresholds directly — it is not a capacity-tracking circuit. A new Ni-MH cell can hold a surface charge that reads full immediately after charging but settles lower once the pack rests for 30–60 minutes. This resting voltage, not the peak charge voltage, is what the radio samples for the bar display. Let the pack rest in the radio for one hour after the first charge cycle, then key up briefly — the display will stabilise at the correct level once the cells have settled to their true open-circuit voltage near 8.2–8.4V.