About this replacement
Motorola MTP810Ex / MTP850Ex — 7.4V Li-ion Replacement Battery (NNTN7383)
This is a 7.4V Li-ion replacement battery rated at 720mAh (5.33Wh) for the Motorola MTP810Ex and MTP850Ex portable two-way radios. It slots directly into the same battery bay and uses the same connector and BMS handshake protocol as the original NNTN7383 and NNTN7383A packs. Capacity figures are taken from the product specification — not estimated from web sources.
- MTP810Ex and MTP850Ex compatibility: Both models share the same 7.4V battery rail, physical form factor, and BMS communication interface. A single pack covers both platforms without any modification to the radio or charger dock.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the MTP810Ex platform. The BMS negotiated correctly with the charger dock, accepted full charge without fault LED, and held stable voltage across simulated PTT transmit cycles.
- First insertion on the MTP810Ex dock: If the dock shows a fault LED on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The MTP810Ex platform requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the MTP810Ex cuts out mid-transmission on a freshly inserted pack
A new Li-ion cell ships at storage voltage — typically 3.6–3.7V per cell, not the 4.2V peak of a fully charged pack. When PTT is pressed, transmit current spikes sharply. If the cell voltage is already at storage level, that spike can pull the pack below the BMS low-voltage cutoff threshold, tripping a momentary shutdown mid-transmission. This is not a fault with the pack. Charge the battery fully in the dock before the first shift and the cutoff will not trigger under normal TX load.
Bar indicator showing one fewer bar than expected after a full charge cycle
The MTP810Ex uses a voltage-threshold bar indicator — it reads bar count directly from pack terminal voltage, not a fuel gauge chip. A new cell that has not yet completed its first full charge cycle will rest slightly below the top threshold, displaying one bar less than expected even after the dock shows green. Run one complete charge cycle to the dock's green indicator, then allow the pack to rest for 15 minutes off the dock. Terminal voltage will settle above the top threshold and the indicator will read correctly.