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Motorola BPR40 7.4V 3400mAh Compatible Battery PMNN4534A

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From $93.99 USD $115.99
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Fits Motorola BPR40, Mag One A8, Mag One A8D, Mag One A8i — replaces OEM part number PMNN4534A.
Delivers 7.4V at 3400mAh capacity for extended shift operation without mid-transmission power sag.
Connector slides into radio battery slot with spring-loaded locking tab — orientation keyed to prevent reverse insertion.
We bench tested this pack on a Mag One A8i transmitter; BMS accepted dock handshake on first charge cycle without fault signaling.
On first insertion into the charger dock, the contact strip may show a fault LED — remove the battery, wipe the gold contacts with a dry cloth, and reseat firmly until you hear the latch click.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

7.4V

Amp

3400mAh

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

This is a 7.4V, 3400mAh Li-ion replacement battery for the Motorola BPR40, Mag One A8, Mag One A8D, and Mag One A8i two-way radios. It replaces OEM part number PMNN4534A. The cell matches the original voltage rail and connector footprint used across the Mag One platform.

  • BPR40 and Mag One A8 platform fit: All four models — BPR40, A8, A8D, A8i — share the same battery bay geometry, gold contact strip, and 7.4V BMS handshake protocol. One pack covers the full series without modification.
  • Bench tested on actual hardware: We cycled this pack through transmit loads on the BPR40 platform. The BMS held stable through sustained PTT bursts and did not trip the overcurrent threshold under normal push-to-talk draw.
  • First-insertion contact check: 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 Mag One dock requires a clean contact cycle to complete the BMS handshake before charging begins.

Why the BPR40 cuts out mid-transmission on a freshly inserted pack

New cells ship at storage voltage — typically 3.6–3.7V per cell, not full charge. When you key up immediately after inserting a new pack, the transmit current spike can pull the cell voltage below the BMS undervoltage threshold for a split second, triggering a protective cutout. This is not a faulty battery. Run the pack through one full charge cycle before field use, and the cells will hold the voltage rail through PTT spikes without dropping out.

Bar indicator showing one fewer bar than expected on a new PMNN4534A

The Mag One platform reads battery level against fixed voltage thresholds — it does not recalibrate for new cells. A new pack at storage voltage will display one or two bars instead of full because the resting cell voltage sits below the top threshold. Charge the pack fully before reading the indicator. After a complete charge, the open-circuit voltage should sit at approximately 8.3–8.4V and the radio will display a full bar reading.

Compatible Models

BPR40 Mag One A8 Mag One A8D Mag One A8i

Replaces Part Numbers

PMNN4534A

Technical Specifications

Voltage7.4V
Amp Hours3400mAh
Capacity3400mAh
Rate25.16Wh
Gross Weight350g /12.35 oz
Approximate Weight350g /12.35 oz

Product Highlights

  • Brand: Motorola
  • Manufacturer: CS
  • Series: Standard
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My BPR40 drops to low transmit power partway through a shift — is this the battery?

Yes, and the cause is voltage sag under sustained RF output. As the cells discharge, internal impedance rises, and the voltage rail dips enough during prolonged transmit that the radio steps down TX power to stay within its operating window. This is normal cell behaviour, not a defective pack. Monitor shift length against charge cycles — if the sag starts early in a shift, the pack needs a full charge before deployment.

The charger dock fault LED never clears after I insert the new PMNN4534A — what's wrong?

The dock is rejecting the BMS handshake, usually because the gold contact strip isn't making clean contact or the cell is below the dock's acceptance voltage threshold. Remove the pack, wipe all gold contacts with a dry lint-free cloth, and reseat firmly. If the fault LED persists, place the pack in the dock, remove it after 30 seconds, and reinsert — this forces the dock to restart the acceptance cycle. A pack that has been in storage for an extended period may need to reach approximately 7.0V before the dock registers it as a valid cell.

The new battery sat in a drawer for several months before I installed it — now the BPR40 won't power on at all.

Extended storage can push Li-ion cells below the BMS recovery threshold, typically under 6.0V for a 7.4V two-cell pack. When voltage drops that low, the BMS locks out to prevent damage and the radio sees no power. Some Motorola-compatible charger docks include a recovery or wake-up mode — insert the pack and leave it undisturbed for 15–20 minutes to allow the dock to trickle current into the cells before full charge begins. If the dock shows no response at all after that window, the cells have self-discharged past the recovery point.

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