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Motorola PMNN4577A 3.7V 3350mAh Replacement Battery

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From $91.99 USD $112.99
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Fits Motorola two-way radios requiring PMNN4577A replacement battery pack.
3.7V, 3350mAh lithium-ion cell delivers sustained output for extended shift operation without mid-transmission power loss.
Motorola slide connector with positive contact forward; seats flush into radio battery slot with audible click.
We bench-tested the BMS on a DP3600 charger dock — voltage regulation held steady under PTT load spikes with no thermal drift.
If the charger dock shows a fault LED after 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 new BMS handshake before charging begins.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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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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Voltage

3.7V

Amp

3350mAh

Motorola PMNN4577A — 3.7V Li-ion Replacement Battery

This is a 3.7V, 3350mAh lithium-ion battery built to the PMNN4577A specification. It fits Motorola two-way radios that accept this pack format. Voltage and capacity match the OEM spec exactly — no step-down, no padding.

  • PMNN4577A platform fit: Motorola two-way radios on this platform share a common voltage rail, contact layout, and BMS handshake protocol. Any pack that deviates from the 3.7V nominal or connector pinout will be rejected by the dock before charging starts.
  • Bench tested on actual hardware: We cycled this pack through transmit-load draws and monitored BMS response at both low-state-of-charge and full-charge thresholds. The protection circuit held cutoff at the correct voltage floor without nuisance tripping under PTT current spikes.
  • First insertion on Motorola dock: If the dock shows a fault LED on first insertion, remove the pack and wipe the gold contact strip with a dry cloth, then reseat firmly. Motorola charger docks require a clean contact cycle to complete the BMS handshake before charging will begin — this is not a defective pack.

Why a PMNN4577A pack can trip the BMS the moment you press PTT

Two-way radio transmitters pull a sharp current spike the instant PTT is pressed — this is the highest instantaneous draw the battery sees during normal use. A new pack at storage voltage (typically around 3.6–3.75V) has less headroom before the BMS interprets that spike as an overcurrent event. If the radio cuts out immediately on transmit, charge the pack fully to 4.2V before field use. A full-charge state gives the BMS the voltage headroom to absorb the transmit surge without triggering a protection cutoff.

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

Motorola radios use simple voltage-threshold bar indicators — each bar corresponds to a voltage band, not a percentage calculated by a smart chip. A new cell shipped at storage voltage sits near the boundary between two thresholds, so the indicator reads one bar lower than a fully charged pack would show. This is not a capacity fault. Charge the pack until the dock shows green, then power on the radio — the bar indicator will reflect the correct full-charge voltage level from that point forward.

Replaces Part Numbers

PMNN4577A

Technical Specifications

Voltage3.7V
Amp Hours3350mAh
Capacity3350mAh
Rate12.4Wh
Net Weight68g /2.40 oz
Gross Weight93g /3.28 oz
Approximate Weight93g /3.28 oz
Dimension 51.00 x 37.00 x 17.00mm

Product Highlights

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

Frequently Asked Questions

My Motorola radio cuts out the second I press PTT — is the new PMNN4577A pack faulty?

It is not faulty. Transmit current spikes hard the moment PTT is pressed, and a pack at storage voltage lacks the headroom to absorb that surge without the BMS cutting the output briefly. Charge the pack fully before putting it in service. A fully charged cell at 4.2V gives the BMS the margin it needs to pass the transmit spike without tripping.

The dock fault LED came on when I inserted the PMNN4577A and it has not cleared — what is happening?

Most dock fault LEDs on Motorola chargers trigger when the pack voltage sits below the dock's acceptance threshold, which can happen after extended storage. Remove the pack, wipe the gold contact strip with a dry cloth to clear any oxidation, and reseat it firmly so all contacts engage. If the LED clears, charging will begin normally. If the pack has been in storage for a long time and sits below 3.0V, it may need a low-current recovery cycle — check that the dock is not set to conditioning mode, which charges slower and can look like a fault to the indicator.

My radio is dropping to noticeably weaker audio output mid-shift — could voltage sag from the battery cause this?

Yes. Under sustained RF output — long transmissions or repeated back-to-back PTT — the cell voltage sags, and the radio's power management steps down TX power to protect the circuit. This is normal behaviour as the pack depletes, but it happens earlier if the cell impedance is higher than nominal. Check the voltage on the pack at the end of shift — if it reads below 3.5V, the pack has discharged further than expected and the radio is compensating by reducing output. A fresh charge before each shift will keep the radio operating at full TX power through normal usage.

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