Motorola FNB-Z165 Replacement Battery 7.4V 1600mAh

Motorola VZ-10 / VZ-18 / VZ-12 — 7.4V Li-ion Replacement Battery (FNB-Z165)

The FNB-Z165 is a 7.4V, 1600mAh Li-ion battery for the Motorola VZ-10, VZ-18, and VZ-12 two-way radios. It slots directly into these compact handhelds and communicates with the radio's BMS handshake over the same connector as the original pack. Capacity is rated at 11.84Wh.

• VZ-10, VZ-18, and VZ-12 compatibility: These three radios share the same battery bay geometry, contact pin layout, and 7.4V power rail. The FNB-Z165 BMS is tuned to that shared voltage profile, so the radio's protection circuit accepts the pack without triggering a fault condition on power-up.
• Bench tested on actual hardware: We cycled this pack through transmit loads on the VZ platform. The BMS held cutoff correctly at low-cell threshold and did not trip during the PTT current spike at full RF output. Cell voltage balanced within two cycles.
• First insertion on a Motorola dock: If the charger dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola VZ dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.

Why the VZ-10 cuts out mid-transmission on a freshly inserted FNB-Z165

A new Li-ion cell ships at storage voltage — typically 3.6–3.7V per cell, not the 4.2V peak of a full charge. When PTT is pressed, the VZ-10 pulls a sharp transmit current spike. At storage voltage, internal cell resistance is higher, which causes a momentary voltage dip. If that dip crosses the radio's low-voltage cutoff threshold, the radio drops the transmission or mutes the output entirely. The fix is to charge the pack fully before your first use shift — one complete charge cycle brings cell voltage and impedance to operating spec.

Bar indicator showing one fewer bar than expected after fitting the FNB-Z165

The VZ series uses a simple voltage-threshold bar indicator — each bar maps to a specific resting voltage range. A new pack at storage voltage reads lower on that scale than a fully charged pack, so the display shows one bar below what you'd expect. This is not a faulty cell or a capacity issue. Charge the battery fully in the dock until the charge LED goes solid green, then reinsert — the indicator will reflect the correct resting voltage of approximately 8.3–8.4V and display accordingly.