I obviously missed this thread and the deleting of the first post makes much of the discussion meaningless but the inevitable result of any discussion on 12v fridges gets around to batteries and charging.
The greatest misconception is that solar panels charge at the rated amps and the amount of time they contribute then that if you use x amount of amps you only need to put back in the same amount, all the above are similar to the discussion of how long is a piece of string.
After many years travelling and relying on battery power I have been proved wrong so many times it's just not funny, my conclusion is in part that batteries must be kept fully charged, batteries depending on type need much longer than what the discharge rate was than what the charger rate is supposed to be to recharge.
As for fridges again the variables are just so many that it is almost impossible to give a simple answer but I prefer a fridge that is capable of providing a rapid drop in temperature, of course this will mean a higher current draw but for a shorter time the manufacturers give an amp rating per 24 hr average but it is meaningless even if you have figures used to obtain that result as in practice especially on a boat the factors are constantly changing but the lower you want the temperature in the cabinet has a very non linear effect on the amps used and therefore the supply required.
Imho the only way to be safe is to have multiple methods of charging, good meters and good batteries capable of holding enough charge in the worst scenario but most importantly the ability to be flexible.
We use two house batteries of 100ah and still have the original start /house battery 55 ah? (2006)as a starting battery, we can charge from two 65w panels, a Christy 50 amp honda powered charger, a C-Tek 25 amp charger and of course the 20 odd amps from the Etek which is variable depending on revs, we also use a 2000w pure sine wave inverter to power the C-tek from the trucks 12v when travelling ensuring that when we pull up for the night on water or land we are fully charged at least once a day.
If we are anchored for a period we will charge with the Christy in the morning to get maximum draw from the batteries and rely on the panels to hopefully reach float by dusk, the time we run the Christy depends on what the usage is for the previous night, from memory the panels put in about 24 amps on a normal northern australia dry season day.
Edit only once this year did the Christy stall ie have over 50 amps battery draw, usually it was 32 amps dropping to about 8 prior to switching off, these are the best batteries we have used and being calcium have a quick charge rate when needed.
http://www.ebay.com.au/itm/4WDEXTREME-1 ... 4ac1de4400
I often get the facts mixed up
I would be more inclined to think that I am wrong first - but I will check it out.
