Motorola XTS1500 Replacement Battery NTN9815 7.4V 3000mAh

Motorola XTS1500 / XTS2500 / MT1500 — 7.4V Li-ion Replacement Battery (NTN9815)

This 7.4V 3000mAh Li-ion pack replaces a long list of Motorola OEM part numbers including NTN9815, NTN9815A, NNTN7335, NNTN7554, and NNTN9858, among others. It fits the XTS1500, XTS2500, PR1500, and MT1500 P25 portable radios. Voltage and cell chemistry match Motorola factory spec exactly.

• XTS and MT platform compatibility: The XTS1500, XTS2500, PR1500, and MT1500 share the same battery bay geometry, connector pinout, and BMS handshake protocol — that is why one pack covers all four platforms. The radio's firmware reads voltage thresholds from the battery BMS directly; a matched 7.4V cell string clears that handshake on first insertion.
• Bench tested on actual hardware: We ran this pack in an XTS1500 and cycled through repeated PTT transmit bursts to stress the BMS overcurrent protection. The pack held voltage within spec under sustained transmit load and the BMS did not trip or latch off during any test cycle.
• First insertion contact check: If the charger dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Motorola dock requires a clean contact cycle to complete the BMS handshake before it will begin a charge cycle.

Why the XTS1500 cuts out mid-transmission on a new battery

The XTS1500 draws a sharp current spike the instant PTT is pressed — RF output ramps up in milliseconds. If the BMS detects that spike as an overcurrent event, it trips and disconnects the cell string before the radio can complete the transmission. This is not a radio fault; it is the BMS responding to a current surge it interprets as a short. Most trips on a brand-new pack happen because the cells shipped at storage voltage, around 3.6–3.7V per cell, and internal resistance is slightly higher at that state of charge. Running one full charge cycle before heavy PTT use brings cell impedance down and stops the trip from recurring.

Bar indicator showing one fewer bar than expected after a fresh charge

The XTS platform uses simple voltage-threshold logic to drive the bar indicator — it reads pack terminal voltage and maps it to bars, nothing more. A new pack fresh off its first charge may read 8.2–8.3V at the terminal rather than the 8.4V peak, because the charger dock terminates early if it does not yet trust the BMS profile. The radio then displays one bar short of full, which looks like a fault but is not. Remove the pack, reinsert it, and place it back on the dock for a second full charge cycle; terminal voltage will reach 8.4V and the indicator will show correctly.