Thanks Tony.
And Bod
I reckon it's down to not fully charging the batteries while off grid. After shore power the batteries hold power for much longer. Thanks for your suggestions. I will action both. Clearly don't have to worry about my brain collapsing into a state of retirement with new skills to learn. As I have already purchased new batteries and scrapped the old ones, that's a learning curve cost!
Thanks also Mike.
1&2 noted and 3 would be good if it wasn't so cloudy perhaps. When the the sun is out the solar panels seem to throw out around 20volts although I think the controller limits the charging ability same as the alternator charging issue mentioned by Tony. More personal education needed methinks!
Thanks Sir Nibble. Alternator seems to run fine at around 13.7v (however not long enough issue)
Hi Jim. The fridge is a multi function 240/12v/lpg switched and wired direct to 12v. Just checked again and it's not 35w but 110w power consumption. Starting to think this is the power drain issue. Will have to work out the amount of power relative to time/volts this uses.
Is there a simple equation for this? (Homework reading of (Wotever's Battery Charging Primer )
IF the fridge power consumptiom is the issue. How else do you keep food cool apart from canal storage.
As my wonderful wife tells me - life afloat isn't easy or glamorous, just a great life (if you have funds to B O A T)!