TYT TYT777 Replacement Battery 7.4V 1200mAh Li-ion

TYT TYT777 / PX-777 / MT-777 Series — 7.4V Li-ion Replacement Battery

This is a 7.4V 1200mAh Li-ion replacement battery for the TYT TYT777, MT-777, PX-777, and PX-728 series handheld two-way radios. It slots into the same battery bay as the original pack and connects via the same contact layout. Capacity is 1200mAh — use what's listed here, not figures quoted elsewhere.

• TYT777 / PX-777 / MT-777 platform fit: These models share a common battery form factor, contact arrangement, and BMS handshake protocol across the UHF and VHF variants. One pack covers the group because the voltage rail and connector spec didn't change across that production run.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on a TYT777-class radio body. The BMS held cutoff correctly at the low-voltage threshold and accepted charge from a standard dock without triggering fault states.
• First-insertion contact check: If the charger shows no activity on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating. New cells ship at storage voltage — the dock needs a clean contact cycle to register the pack and begin the charge sequence.

Why the TYT777 cuts out mid-transmission on a new battery

Pressing PTT draws a sharp current spike as the RF stage fires up — on the TYT777 platform this can hit two to three times the idle draw in under a millisecond. If the cell is still at storage voltage (typically 3.6–3.7V per cell), the BMS may read that spike as an overcurrent event and trip the protection circuit. The radio goes silent even though the pack isn't flat. Charge the battery fully before the first transmission cycle — once the cells are at rated voltage, the BMS handles the PTT spike without tripping.

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

The TYT777 reads battery level using voltage thresholds, not a fuel gauge chip. A new pack at storage voltage sits below the top threshold, so the radio displays one bar fewer than a fully charged cell would show. This isn't a faulty pack — it's the radio reading a real voltage. Charge the battery until the dock light goes solid green, then reinsert. The indicator will step up to the correct bar level once cell voltage reaches 8.3–8.4V.