deep cycle batteries

It'll be less than 195Ah Alex, unless your current draw is very small indeed. Deep cycle batteries are usually rated for their C/20 rate (or C/15 or C/10) = how many amps the battery can supply for 20 (or 15 or 10) hours when fully charged. That figure is obviously larger for the bigger capacity battery, so the smaller battery gets drained well before the bigger one when you run your fridge.
When you get to recharge them, the one that's drained more will soak up most of the charge initially and the bigger battery most likely never gets fully charged.

In other words, its not a good idea what you are doing. The only way batteries in parallel are remotely happy is when both are exactly the same type and age. I do that sometimes with my boat's two indentical batteries, when I need extra power for a short time. They get charged separately from solar panels, only if I connect the 30A genny they are switched in parallel for charging and then only for the first part of the charging cycle.

Klaus

This is a bit of a contraversial one, however from my understanding as long as there is a higher voltage than the batteries charge avaliable to them then both batteries will take what they need. If both batteries are linked in Paralell then they are both going to be at the same voltage when resting anyway as they would have equalized themselves.

ie. Battery A at 12.1V, Battery B at 12.1V Alternator supplying 14V both batteries will charge from that at their own rates. Obviously the bigger battery is going to draw more amps from the alternator than the smaller because it need more power to be put back into it.

Now the only time this becomes a problem is when the charge is stopped (ie engine is stopped). One battery may have charged up to 12.4v (probally the smaller one as it would charge faster) and the other battery may have only got to 12.2V (as it's bigger and takes longer to charge). So when the charge is stopped, the batteries will equialize again. (not real good for either as the load on the smaller one will be large as the bigger one trys to suck the life out of it and the bigger one will get a surge of power from the smaller one which then puts a strain on it.

But hey, lot's of vehicles are setup this way (including mine) and apart from decreasing the life of your batteries a small amount, it's not going to do any other harm. And IMHO the heat generated under the bonnet of a Turbo Diesel 4by working hard in an Oz summer is going to do much more damage than the above proccess anyway. But the extent of it will obviously depend on several things, a) how bigger difference there is in the batteries capacity. b) How long you reguarly charge them (drive the car) before stopping the charge.

If the batteries are similar in capacity the voltage variation between the two would not be that great anyway.

Others opinions may, no WILL differ. ;-)

Jeff M is correct.

Each battery will draw charge current according to its needs. If you don't believe me go to my website (as above except www.) and click the Link to Ample Power Company (a leading US maker of three-stage chargers etc). You will find they say almost exactly the same.
Collyn Rivers