Battery Voltage

Thanks,
So would that be the reason it dropped from 13.8V to 10V when connected ???

RegReagan

it's a bit hard to tell what your battery problems are, could be a defective cell like ABR suggested.

You can do the following which should clear things up:

connect the battery to a mains powered charger and let it charge.

Because your charger mightn't be able to handle a defective battery without acting strangely (like blowing a fuse or going up in flames!), do this in an area which offers a safe distance from combustible materials.

Keep an eye on everything voltage and temperature, and don't go to bed, meaning don't do this overnight.

After several hours of charging, you can disconnect the charger from the battery and check the open circuit voltage.
It should read at least a touch over 12V. Let the battery rest for half an hour and recheck the voltage, it should still show around 12V.
Now you can confidently put it on charge again for 24 hours or so.

Stop charging, and check the voltage across the battery terminals in open circuit. You want to see between 12.6 and 13.2V.
Connect some light loads like 12V lights and check the voltage, connect it to the fridge and see what the voltmeter reads.

If the voltage holds above 12.2 to 12.6V under load, there is still hope.
If not, the battery's pretty much had it.
You can try another 24 hour charging session but chances are it won't come back any more.

Best regards, Peter