I need some advice as to best set up my batteries and what option would be best with what I have already here.

I currently have 3 batteries in my car and this is from when the car was petrol and could only fit a small battery as the aux but now I have a 105a under the bonnet but still have an 85a in the back.

I have a 90amp alternator (new) and a basic isolator (my redarc died).

The 105 and 85 are joined together on one side and then of course the cranking battery, Matty said I should join the 2 big batteries together permanently and have the 85a in the back as the aux with a DC to DC charger but I do not have the money to buy one at this point in time.

I have fridge, oven, and rear light plus lots of smaller stuff running from the 2 aux batteries.

A couple of people have told me to lose the third battery now I have a diesel?

I have a 40watt solar panel plus another 180w I will only use when camping for extended periods.

There are a few different ways to go but I struggle with electrics so would love some advice.

Cheers