Hi everyone,

I’m having a strange issue with my Sena 50S and I’m trying to figure out whether this is a battery problem or a hardware failure.

After charging, the Sena turns on normally and reports that the battery level is high, but after about 3–5 seconds it says “Goodbye” and switches off.

I’ve already tried:

• Fault Reset

• Different USB cables

• Different chargers

• Turning it on while connected to a charger

• Holding the Phone button after startup

Nothing changes — it still shuts down after a few seconds.

Another strange symptom is that when I connect the charging cable, the LED does not light up at all — neither red nor blue.

The unit is about 5 years old. Around a year ago I replaced the original battery because it was worn out and had lost capacity. The replacement battery is a Cameron Sino YT102540P / CS-SMH300S, and it worked perfectly fine for about a year without any issues.

I also found the existing thread about 50S units shutting down shortly after startup, but the suggested workaround of holding the Phone button does not work in my case.

Video showing the issue:
[YouTube link]

Has anyone experienced exactly the same combination of symptoms?

I’d especially like to know if the cause turned out to be:

• the battery

• USB-C port

• charging/power-management circuit

• main board

• firmware

Any advice or repair experience would be appreciated.