Kenwood UPB-4L Two-Way Radio Replacement Battery 3.7V 1050mAh

Kenwood UBZ-BH47FR / TCP-U90F / UBZ-RJ27 — 3.7V Li-ion Replacement Battery (UPB-4L)

This is a 3.7V, 1050mAh lithium-ion battery built to the UPB-4L specification. It fits the Kenwood UBZ-BH47FR, TCP-U90F, and UBZ-RJ27 handheld radios. These are compact short-range two-way radios used by event staff, security teams, and small business operations.

• UBZ-BH47FR / TCP-U90F / UBZ-RJ27 platform fit: All three models share the same slim 3.7V single-cell architecture, battery bay dimensions, and contact pin layout. One UPB-4L battery serves the full group without modification or adapter.
• Bench tested on actual hardware: We ran this pack through charge and transmit cycles on the UBZ-BH47FR. The BMS handled PTT-triggered current spikes without tripping, and the dock accepted the pack's BMS handshake cleanly across repeated insertion cycles.
• First-insertion contact cycle on Kenwood docks: If the charger shows a fault LED on first insertion, remove the battery and wipe the gold contact strip with a dry cloth. Reseat the pack firmly. The Kenwood dock needs a clean contact cycle to complete the BMS handshake before it begins charging.

Why the UBZ-BH47FR bar indicator reads low on a brand-new UPB-4L

New lithium-ion cells ship at storage voltage — typically around 3.6–3.7V — not at full charge. The UBZ-BH47FR uses a simple voltage-threshold bar indicator, so a pack at storage voltage will show one or two bars instead of three. This is not a fault with the battery. Run the pack through a full charge cycle in the dock before drawing conclusions about its condition.

UBZ-BH47FR drops transmit power mid-shift on a replacement pack

Sustained RF output draws significantly more current than standby or receive modes. If the replacement cell has higher internal impedance than the original — common in cells that sat in storage — voltage sags under that load and the radio steps down TX power to protect the circuit. The fix is to condition the pack: charge it fully, run it through two or three normal use cycles, and impedance typically settles. If sag persists after three cycles, check cell voltage under PTT load — it should stay above 3.4V.