I have a SU3000 that works from AC power and inverter will start if you remove power, but it wont start up from battery power.

Originally I didn't have batteries to test it so I used a couple of small power supplies in series to produce the 48V it requires to operate. They were only a 1 amp supply or so but it worked.

Now with nothing plugged in, it draws a lot more amperage on startup from battery and instantly goes to overload..
When using the power supplies I originally used to start it up, it draws too much power from them and they shut down, and it doesn't get a chance to do anything but beep once and the lights blink once.


So obviously the unit is using more power than before and not just a software issue.


I am thinking it may have a bad mosfet. Cant remove them until I get my hot air station. Does this seem like a reasonable place to start troubleshooting? Maybe the mosfets were damaged from using the power supply to power the unit?

Thanks in advance for any advice