About this replacement
Motorola GP329 EX / GP340 ATEX Series — 7.4V Li-ion Replacement Battery (NNTN5510)
This is a 7.4V, 1500mAh Li-ion replacement battery for the Motorola GP329 EX, GP340 ATEX, GP340 Ex, and GP380 ATEX series portable two-way radios. It replaces OEM part numbers NNTN5510, NNTN5510AR, NNTN5510BR, NNTN5510CR, and NNTN5510DR. Physical dimensions are 123.52 × 58.70 × 35.80mm — confirm your original battery matches before ordering.
- GP329 EX and GP340 ATEX platform fit: These ATEX-rated radios share a common battery bay, connector pinout, and BMS handshake protocol across the GP329 EX, GP340 ATEX, GP340 Ex, and GP380 ATEX. One pack covers the full group because the voltage rail and communication interface are identical across each variant.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge on GP340 ATEX hardware. The BMS responded correctly to charge termination, held voltage within spec under transmit load, and tripped overcurrent protection as expected on a hard PTT press.
- First-insertion contact check: Before seating the pack in the charging dock for the first time, wipe the gold contact strip on the battery with a dry cloth. The GP329 EX and GP340 ATEX docks require a clean contact surface to complete the BMS handshake — a contaminated contact strip will trigger the fault LED and prevent charging from starting.
Why the GP340 ATEX cuts out mid-transmission on a new NNTN5510
A new cell ships at storage voltage — typically around 3.7–3.8V per cell, not full charge. When you press PTT, transmit current surges sharply. If the pack hasn't been through a full charge cycle first, that surge can push cell voltage below the BMS overcurrent threshold, tripping a protective cutoff mid-transmission. This isn't a faulty battery. Charge the pack fully in the dock before first use on shift, and the BMS will hold cleanly under normal PTT loads.
Bar indicator shows one fewer bar than expected after inserting a new NNTN5510
The GP329 EX and GP340 ATEX use a voltage-threshold bar indicator — each bar corresponds to a voltage band, not a measured capacity percentage. A new pack at storage voltage reads lower than a freshly charged pack, so the radio correctly shows fewer bars. This is not a defect. Put the battery through one full charge cycle in the dock and voltage will rise to the full-charge band, which the radio will display as a full bar reading — typically 8.2–8.4V at termination.