About this replacement
Motorola GP328 Plus / GP338 Plus Series — 7.4V Li-ion Replacement Battery (JMNN4023)
This 7.4V, 2600mAh Li-ion pack replaces the original battery in the Motorola GP328 Plus, GP329 Plus, GP338 Plus, GP344, and more than 20 compatible variants. It matches the OEM connector, contact strip, and BMS handshake profile the radio's charger dock expects. Capacity figure is taken from the product specification — 2600mAh / 19.24Wh.
- GP300 Plus platform compatibility: The GP328 Plus, GP329 Plus, GP338 Plus, and GP344 share a common battery bay geometry and the same 7.4V rail. The charger dock authenticates through the gold contact strip, so connector alignment and BMS voltage thresholds must match — this pack meets both.
- Bench tested on actual hardware: We ran this pack through a transmit-cycle load on the GP338 Plus bench unit. The BMS held the voltage rail steady through repeated PTT events and tripped the overcurrent protection cleanly at the expected threshold — no false lockouts recorded.
- First-insertion contact cycle: If the charger dock shows a fault LED on the first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola dock requires a clean contact surface to complete the BMS handshake before it will begin charging.
Why the GP328 Plus cuts out mid-transmission on a new battery
During transmit, the GP328 Plus draws a sharp current spike the moment PTT is pressed — RF output and the PA stage both pull from the same cell stack simultaneously. If the BMS reads that spike as an overcurrent event, it trips and drops the radio off-air for a split second. This usually happens when the pack is cold or has been sitting at storage voltage for an extended period. Let the pack complete one full charge cycle in the dock before field use — this brings the cell voltage up to the operating range where the BMS handles transmit spikes without tripping.
Bar indicator showing one fewer bar than expected on a new pack
The GP328 Plus uses a voltage-threshold bar indicator — each bar corresponds to a voltage band, not a calculated charge percentage. A new pack shipped at storage voltage (typically around 3.7V per cell) will read lower than a freshly charged pack, so the display may show one or two bars even though the cells are not depleted. This is not a cell fault. Seat the pack in the dock, allow a complete charge cycle until the dock LED goes solid green, then reinsert — the indicator will reflect the correct voltage level.