Motorola BPR40 Replacement Battery 7.4V 2600mAh Li-ion

Motorola BPR40 / Mag One A8 Series — 7.4V Li-ion Replacement Battery (PMNN4534A)

This is a 7.4V, 2600mAh Li-ion battery replacing the PMNN4534A pack used in the Motorola BPR40, Mag One A8, Mag One A8D, and Mag One A8i portable radios. It uses the same cell configuration and connector as the original, so it seats and locks into the radio body without modification. Capacity is rated at 2600mAh (19.24Wh), matching the OEM specification.

• BPR40 and Mag One A8 platform fit: These four models share the same battery bay geometry, contact layout, and 7.4V nominal voltage rail. The BMS handshake across all four uses the same communication protocol, so one pack covers the entire group without any wiring or adapter change.
• Bench tested on actual hardware: We ran this pack through a full charge and discharge cycle on the BPR40 platform and monitored the BMS during PTT transmit bursts. The overcurrent protection tripped correctly at threshold and reset without manual intervention between cycles.
• First insertion into the charger dock: If the dock shows a fault LED when you seat this pack for the first time, remove it, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola charger platform requires a clean contact cycle to complete the BMS handshake before it begins charging.

Why the BPR40 cuts out mid-transmission on a new PMNN4534A pack

A new Li-ion cell ships at storage voltage — typically 3.6–3.7V per cell, not full charge. When the radio fires a PTT transmit burst, current draw spikes sharply. If the cell voltage is already low, the BMS reads this spike as an undervoltage fault and cuts the output to protect the cells. The radio goes silent even though the pack is not defective. Charge the pack fully before first use — the dock should reach a steady green at approximately 8.4V across the pack before you trust it in the field.

Bar indicator showing one fewer bar than expected after inserting a new pack

The BPR40 and Mag One A8 series use a simple voltage-threshold bar indicator — each bar corresponds to a voltage band, not a calibrated capacity reading. A new pack at storage voltage sits in a lower band and the radio displays one or two bars even though the cells are healthy. This is not a fault with the pack. After a full charge cycle the voltage rises above the top threshold and the indicator shows the correct bar count.