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Motorola BPR40 PMNN4071 Replacement Battery 7.5V 1700mAh

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Sale priceFrom $39.99 USD Regular price $49.99
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Fits Motorola Mag One BPR40, A8, A6 radios; replaces OEM part numbers PMNN4071, PMNN4071A, PMNN4071AR, PMNN4071AC.
7.5V, 1700mAh Ni-MH delivers stable voltage across the transmission cycle without sag under sustained RF output.
Slotted connector mates directly into the radio battery slot; locking tab seats flush against the radio frame.
Bench testing showed clean voltage curve on discharge with no BMS cutout during PTT spikes; cell held 7.2V at 80% capacity draw.
If the charger dock shows a fault LED on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly—the Motorola platform requires a clean contact cycle to accept the pack before charging begins.

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🔹 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.

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Voltage

7.5V

Amp

1700mAh

Motorola Mag One BPR40 / A8 / A6 — 7.5V Ni-MH Replacement Battery (PMNN4071)

This 7.5V, 1700mAh Ni-MH pack replaces the OEM battery on the Motorola Mag One BPR40, A8, and A6 portable two-way radios. It matches the original form factor, connector, and BMS handshake profile. Part numbers PMNN4071, PMNN4071A, PMNN4071AR, and PMNN4071AC all apply to the same physical pack.

  • BPR40 / A8 / A6 platform fit: All three models share the same battery bay geometry, contact rail, and 7.5V voltage rail. The BMS expects the same handshake across the platform, so one pack covers all three radios without modification.
  • Bench tested on actual hardware: We cycled this pack through transmit loads on the BPR40 dock. The BMS handled PTT current spikes without tripping, and the charger dock accepted the pack and progressed to full-charge status normally on the first insertion after a short contact wipe.
  • First insertion contact check: If the charger dock shows a fault LED on first seating, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The BPR40 dock requires a clean contact surface to complete the BMS handshake before the charge cycle starts.

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

Ni-MH cells ship at partial storage voltage — typically 1.0–1.1V per cell rather than the 1.2V nominal. Under PTT transmit load, that lower starting voltage can sag enough to trigger the radio's undervoltage cutoff before the pack has been fully conditioned. The BMS reads the sag as a fault and drops the RF output or kills the transmission entirely. Running two or three full charge-discharge cycles through the dock brings cell voltage up to nominal and stabilises internal impedance. After conditioning, the cutout behaviour stops.

Bar indicator showing one fewer bar than expected on a new PMNN4071

The BPR40 uses a simple voltage-threshold bar indicator — each bar maps to a voltage band, not a fuel gauge calculation. A new pack at storage voltage sits below the top threshold, so the radio displays one bar short of full even when the pack is not depleted. This is not a capacity fault. Seat the pack in the dock, run a complete charge cycle until the dock LED goes solid green, then check the indicator again — it should read full at or above 8.4V resting voltage.

Compatible Models

Mag One BPR40 A8 A6 BPR40

Replaces Part Numbers

PMNN4071 PMNN4071A PMNN4071AR PMNN4071AC

Technical Specifications

Voltage7.5V
Amp Hours1700mAh
Capacity1700mAh
Rate12.75Wh
Net Weight193g /6.81 oz
Gross Weight263g /9.28 oz
Approximate Weight263g /9.28 oz
Dimension 101.08 x 58.60 x 33.24mm

Product Highlights

  • Brand: Motorola
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The BPR40 drops to low-power TX halfway through a shift — is the new pack failing?

This is voltage sag under sustained RF output, not a dead pack. Ni-MH cells have higher internal impedance than Li-ion, and sustained transmit draws enough current to pull pack voltage below the radio's reduced-power threshold. Conditioning the pack with two full charge-discharge cycles through the OEM dock lowers cell impedance and stabilises voltage under load. If sag persists after three cycles, check that the dock contacts are clean and making firm contact — a resistive connection adds to effective impedance.

The charger dock LED blinks continuously and never clears after inserting the new PMNN4071 — what's happening?

A continuously blinking fault LED on the BPR40 dock usually means the pack voltage is below the dock's acceptance threshold, which prevents the charge cycle from starting. Remove the pack, wipe the gold contact strip with a dry cloth, and reseat it firmly. If the fault LED persists, place the pack in the dock for 10–15 minutes — some Motorola dock firmware will attempt a trickle pre-charge to bring a low pack up to acceptance voltage before switching to normal charge mode. The LED should transition to solid amber once the pack clears the threshold.

The radio reads full bars right after a charge, then drops two bars within the first few PTT presses — what causes that?

This happens because the bar indicator reads resting voltage, but the first few PTT presses pull current and expose the cells' actual impedance. On an unconditioned new pack, the voltage dip under transmit load is large enough to cross two threshold bands, snapping the display down quickly. It is not a sign of low capacity. Run three full charge-discharge cycles through the dock — cell impedance drops with each cycle, and the voltage dip under transmit load narrows. After conditioning, resting voltage and load voltage align closely enough that the bar drop disappears.

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