Error code 309

Hello guys, I got an Superbase V 6400. I receive an error code 309, when I start the unit. What does it mean?

I can not recharge the unit with the AC Input. Only 12v DC Input

What happens if you completely reset your SBV?

How can I completely reset the SBV?

Disconnect all inputs then press and hold the power button for 15+ seconds.

Thank you! This solved my problem