Kenwood PB-40 TK-2118 Replacement Battery 7.4V 1500mAh

Kenwood TK-2118 / TK-3118 — 7.4V Li-ion Replacement Battery (PB-40, PB-41)

This 7.4V, 1500mAh Li-ion battery replaces the Kenwood PB-40 and PB-41 packs used in the TK-2118 and TK-3118 portable two-way radios. It slots into the same battery bay, uses the same gold contact strip, and the BMS speaks the same handshake protocol the radio expects. Capacity is 1500mAh — identical to the original spec.

• TK-2118 and TK-3118 shared battery platform: Both radios run the same 7.4V rail and the same three-pin contact arrangement, which is why Kenwood issued PB-40 and PB-41 to cover both. The connector seats identically in each chassis, and the BMS negotiates with both radio models without modification.
• Bench tested on actual hardware: We cycled this pack through repeated PTT transmit loads — the current spike at key-up sits around 1.8–2.2A, and the BMS held without triggering overcurrent cutoff. Voltage under sustained RF output stayed within the radio's operating threshold throughout the test.
• First insertion into the TK-2118 or TK-3118 charger dock: If the dock LED shows a fault on first seating, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Kenwood dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.

Why the TK-2118 cuts out mid-transmission on a new PB-40 replacement

A new Li-ion cell ships at storage voltage — typically 3.6–3.75V per cell, which puts this 2S pack around 7.2–7.5V. The TK-2118 pulls 1.8–2.2A at PTT, and if the pack hasn't had a full charge cycle, that transmit spike can drag the voltage below the radio's minimum threshold. The radio interprets that as a low-battery condition and cuts RF output or drops the call entirely. Charge the pack to full before the first use — confirmed full charge sits at 8.4V across the pack terminals.

Bar indicator on the TK-3118 showing one fewer bar than expected after swap

The TK-3118 reads battery level by measuring terminal voltage against fixed threshold steps — there is no calibration chip involved. A new pack at storage voltage reads lower than a freshly charged one, so the radio displays one fewer bar even though nothing is wrong with the cell. This is not a faulty battery. Run one full charge cycle to 8.4V, and the bar indicator will reflect the actual state of charge correctly on the next power-on.