Electrical Issues

[DaveWendt]

Over the weekend I trailered to my usual river lot and plugged into my standard 30 amp receptacle. Went in to hear a squealing alarm from the electrical panel. Alarm stopped when when I turned off the 15 amp breaker marked fridge. Put fridge on propane and fridge ran fine. Next day got a low DC alarm on fridge, found my 3 100 AH lithium ion batteries at 10 volts. Turned off inverter and batteries recovered during the day, I assume from solar.
Questions: What is the alarm and how do you silence it other than turning off shore power to fridge. Is there a charger for the batteries connected to the same breaker as the fridge. Should an inverter and fridge on propane deplete 300 AH's over night. Why would anything draw from batteries when on shore power.

Any help is appreciated.

 

[alanmalk]

Lets start with a question for you ...

Over the weekend I trailered to my usual river lot and plugged into my standard 30 amp receptacle.
...
Turned off inverter and batteries recovered during the day, I assume from solar.
...

An inverter takes 12 Volts DC and converts it to 110 Volts AC. Why would you have the inverter turned on when plugged into "your standard 30 amp" outlet?

 

[DaveWendt]

It was left on accidentally.

 

[alanmalk]

A couple of guesses here:
An inverter can easily draw a couple of hundred amps of DC from the batteries. Having both an inverter and shore power providing current at the same time could have very unusual and hard to quantify effects. For example, the AC waveform could be 180 degrees out of phase and the inverter might think it needs to provide all the power needed by the converter (which is trying to charge the batteries at the same time). There are also possibilities for ground loops. (I have accidentally used my small inverter to power the trailer AC system while the converter was on. Don't recall exactly what happened but it was instantly obvious that something was wrong. Perhaps squealing??)

And to answer your specific question - yes, the converter and the fridge are on the same DC breaker.

If everything is working properly now I would consider not worrying about it - just a lesson learned.