About this replacement
Kenwood TK-3130 / TK-3131 — 3.6V Ni-MH Replacement Battery (KNB-27N)
This is a 3.6V, 1100mAh Ni-MH replacement battery for the Kenwood TK-3130 and TK-3131 portable two-way radios. It matches the OEM KNB-27N and KNB-27 part numbers and fits the original battery slot without modification. Voltage and physical dimensions are held to OEM spec so the radio's charging circuit accepts it normally.
- TK-3130 and TK-3131 platform fit: Both models share the same battery bay dimensions, contact layout, and 3.6V supply rail. One battery pack covers both radios — no adapter or wiring change needed.
- Bench tested on actual hardware: We cycled this pack through repeated PTT transmit loads on the TK-3130 platform. The BMS held cutoff voltage steady under the transmit current spike and recovered cleanly each time PTT was released.
- First insertion into the charger dock: If the 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 charger platform requires a clean contact cycle to accept the new BMS handshake before it begins charging.
Why the TK-3130 cuts out mid-transmission on a fresh battery
Pressing PTT on the TK-3130 draws a sharp current spike as the RF stage ramps up. A new Ni-MH cell shipped at storage voltage — typically around 3.4V — sits close to the radio's low-voltage cutoff threshold. When the transmit surge hits, the pack voltage dips briefly below that threshold and the radio drops the transmission to protect itself. This is not a faulty battery. One or two full charge cycles bring the cell voltage up to its working range of 3.6V, and the cutoff trips stop.
Bar indicator showing one fewer bar than expected after a full charge
The TK-3130 uses simple voltage-threshold steps to drive the bar indicator — it reads pack voltage against fixed reference points, not capacity. A new Ni-MH cell that has not yet been fully conditioned will rest slightly below its rated open-circuit voltage even after a charge cycle completes. That lower resting voltage maps to one bar fewer on the display. Run two full charge-discharge cycles and the resting voltage will stabilise at the correct level. Check the open-circuit voltage at the pack contacts — it should read 3.7V or above after a complete charge.