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NNTN8128A Motorola APX-2000 Replacement Battery 7.4V 2300mAh

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From $47.99 USD $59.99
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Fits Motorola APX-2000, APX-3000 portable radios; replaces NNTN8128A, NNTN8128C, NNTN8129AR, PMNN4406AR, PMNN4406BR, PMNN4424, PMNN4424A.
7.4V, 2300mAh lithium-ion delivers sustained transmit power across full shift cycles without mid-RF dropout.
Slides into Motorola radio slot with keyed connector orientation; locking tab seats flush against radio frame.
Bench test showed BMS accepted PTT transmit current spike without cutoff; voltage sag remained within APX platform tolerance.
If charger dock shows fault LED on first insertion, remove battery, wipe gold contact strip dry, reseat firmly—Motorola platform requires clean contact cycle for BMS handshake before charging begins.
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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.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ 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

2300mAh

Motorola APX-2000 / APX-3000 Series — 7.4V Li-ion Replacement Battery (NNTN8128A)

This is a 7.4V, 2300mAh Li-ion battery for the Motorola APX-2000 and APX-3000 portable two-way radios. It replaces OEM part numbers NNTN8128A, NNTN8128C, PMNN4406AR, PMNN4424, and several variants. APX-series radios are P25-capable land mobile radios used by public safety and enterprise teams on extended operational shifts.

  • APX-2000 and APX-3000 compatibility: Both models share the same battery bay geometry, contact pin layout, and BMS handshake protocol. The voltage rail is identical at 7.4V nominal, so one battery SKU covers both platforms without modification.
  • Bench tested on actual hardware: We ran this pack through full charge and transmit-load cycles on APX-series hardware. The BMS negotiated correctly with the radio's power management circuit, and the protection circuit responded properly to simulated PTT current spikes without tripping into lockout.
  • First insertion into the charger dock: If the dock LED flashes fault on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly. The APX charger dock requires a clean contact cycle to accept the new BMS handshake before it begins the charge sequence.

Why the APX-2000 cuts out mid-transmission on a new battery

The APX-2000 draws a significant current surge the instant PTT is pressed — RF output plus audio amplification hit the battery simultaneously. If the new pack arrived at storage voltage (typically around 3.7–3.8V per cell), the BMS may interpret the transmit-load spike as an overcurrent event and trip the protection circuit before the radio can sustain the transmission. This is not a faulty battery. Charge the pack fully to 8.4V before the first use and the BMS will operate within its normal window during PTT events.

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

The APX series reads battery state through simple voltage-threshold levels — each bar corresponds to a voltage band. A new cell shipped at storage voltage sits below the top threshold, so the radio displays one bar fewer than a fully charged pack even though the cell is not depleted. This is expected behaviour at storage voltage, not a capacity defect. Charge the battery fully before reading the bar indicator — once the pack reaches 8.4V, the top bar will register correctly.

Compatible Models

APX-2000 APX-3000 APX2000 APX3000 APX4000 APX4000 and APX4000Li APX4000Li MotoTRBO XPR 3300 MOTOTRBO XPR 3500 MOTOTRBO XPR 7350 MOTOTRBO XPR 7380 MOTOTRBO XPR 7550 MOTOTRBO XPR 7580 XPR 3300 XPR 3500 XPR 7350 XPR 7380 XPR 7550 XPR 7580

Replaces Part Numbers

NNTN8128A NNTN8128C NNTN8129AR NTN8128A PMNN4406AR PMNN4406BR PMNN4424 PMNN4424A

Technical Specifications

Voltage7.4V
Amp Hours2300mAh
Capacity2300mAh
Rate17.02Wh
Net Weight153g /5.40 oz
Gross Weight333g /11.75 oz
Approximate Weight333g /11.75 oz
Dimension 118.70 x 55.00 x 40.30mm

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 APX-2000 drops to low transmit power mid-shift even though the battery looked charged at the start — what's happening?

Sustained RF output over a long shift pulls the cell voltage down gradually, and the APX radio steps down TX power automatically once voltage sags below the threshold for full-power operation. This is the radio protecting itself from a hard shutdown during a live transmission, not a fault in the battery. A cell that has been shallow-cycled repeatedly — charged before it was meaningfully discharged — degrades faster and hits that sag threshold earlier in the shift. Run the replacement pack through at least one full discharge and recharge cycle to let the BMS settle at an accurate resting voltage.

The charger dock fault LED never clears after inserting the new NNTN8128A — it just keeps blinking. What do I do?

A continuously blinking fault LED on the APX charger dock usually means the pack voltage is below the dock's acceptance threshold — typically under 6V — and the charger won't initiate a charge cycle at that level. Remove the battery, wipe the gold contact strip with a dry cloth, and reseat it firmly to rule out a contact issue first. If the fault persists, the pack may need a low-current pre-charge to bring it above the acceptance floor. Try a different APX-compatible charger or a multi-chemistry charger with a recovery mode; once the pack reads above 7.0V, the standard dock should accept it.

The APX-3000 won't stay on after PTT — it shuts down immediately when I try to transmit. Is this the battery or the radio?

This is almost always the battery BMS tripping on the transmit current spike, not a radio fault. PTT draws a sharp, high-current load in the first milliseconds of transmission — if the pack arrived at storage voltage or the cells are cold, the BMS protection circuit can interpret that spike as an overcurrent event and cut power instantly. Charge the battery fully to 8.4V, let it rest at room temperature for 15 minutes, then test PTT again. If shutdown continues after a full charge at ambient temperature, test with a second known-good APX pack to isolate whether the fault is in the radio's PA circuit.

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