Motorola EVX-531 Compatible Battery 7.4V 2600mAh AAJ67X001

Motorola EVX-531 / VX-261 Series — 7.4V Li-ion Replacement Battery (AAJ67X001)

This 7.4V 2600mAh Li-ion battery replaces the AAJ67X001, AAJ68X001, AAK66X501, FNB-V133Li, FNB-V134Li, and FNB-V138Li packs across the EVX-531, EVX-534, EVX-539, and VX-261 series. It fits the same physical slot and connects to the same four-pin contact rail used across these Motorola and Vertex Standard platforms. Capacity is 2600mAh — confirmed against the original spec.

• EVX-531 / EVX-534 / EVX-539 / VX-261 platform fit: These models share the same contact rail geometry, BMS handshake voltage range, and charge-termination protocol — which is why one pack covers all of them. The connector keys and housing dimensions match across the group without modification.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on an EVX-531 body and monitored BMS cutoff behaviour under PTT transmit loads. The protection circuit responded correctly to both overcurrent and thermal events without nuisance tripping.
• First insertion on a Vertex Standard 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 EVX platform requires a clean contact cycle to complete the BMS handshake before charging begins — this is not a faulty pack.

Why the EVX-531 cuts out mid-transmission on a new battery

The EVX-531 draws a sharp current spike the moment PTT is pressed — transmit current can jump to 1.8–2A in under 100ms. A new pack shipped at storage voltage (around 3.7V per cell) has higher internal impedance than a fully charged cell, which causes the BMS to read that spike as an overcurrent event and trip. The fix is a full charge cycle before first field use — a fully charged cell at 4.2V per cell handles the transmit surge without tripping. One complete charge resolves this.

Bar indicator showing one fewer bar than expected on a new pack

The EVX-531 uses a voltage-threshold bar display — each bar corresponds to a voltage window, not a calculated capacity percentage. New cells arrive at storage voltage, typically 3.6–3.75V per cell, which maps to one or two bars even though the pack is not depleted. After a full charge brings each cell to 4.2V, the display will read the correct level. If bars remain low after a verified full charge, check that the dock contact pins are clean and making full contact with the pack strip.