as Dave states, you have left more unanswered questions than questions themselves,
 
(1) what size is the engel 
(2) what size and configuration is the second fridge
(3) what size are the dry cell batterys and how old are they, are they "holding" their charge 
(4) what is the starting voltage of the combined batterys after sunset (after charging has ceased but before power is drawn) 
(5) what is the combined power draw of BOTH fridges
(6) do you have a regulator 

I will attempt to gaze into my crystal ball and assume a couple of things
 
(1) engel is 39 ltr in which case it will draw 2.5 amps for every hour it is running, mine runs roughly half of a 24 hour period on a stinking hot day so we must assume yours does as well so that gives us a total of 30 amps in a 24 hour period not enough to affect the power input of your combined panels, it will run a hell of a lot less on mild to cold days 

(2) if your second fridge is an absorption then why are you running it off 12 volt, run it on gas
 an absorption fridge running on twelve volt will "run" continually, the heating element will quickly flatten your batterys and I think that this is what is going on

disconnect the fridge from the system and run it on gas and I think your problem will dissappear

(3) to answer 4 and 5 above please put some sort of monitoring guages on so that you have a "starting point" for comparison
 
I run my engel (39 ltr) and a couple of lights as well as a 300 watt inverter with tv and dvd easily off my 100 amp hour wet cell battery with only one 80 watt solar panel briefcase, 

we have stayed for a couple of weeks like this with no power loss to the battery you must start with a monitoring station, just a simple amp guage, this tells you what your batterys are doing, from there we can help you to fix any problems

run the absorption fridge on gas and I think all will be apples

-- Edited by dave06 on Monday 4th of May 2009 10:33:19 AM

something does not add up here, given that the fridges are the only things running then I see no problem powerwise

the engel, I know from experience consumes roughly 30 amps per day, the figure of 55 amps given for your waeco is "roughly" correct for a 24 hour period, I would actually state that consumption would be lower than that

given the batteries are three years old then they are coming to the end of their servicable life but still should last quite a while yet

disconnect all power draw, fully charge the batteries, take a reading before night then take another reading the next morning, there should be NO power drop or at least very little

if there is a loss of power then repeat the no power loss test using only ONE battery then redo the test using the other battery, if you have a substantial loss of power then one battery or the other is failing, replace the battery that is failing

this can be the only reason for such a massive power loss that I can see

the system that you describe should well and truly exceed your power usage

as I stated my system is far less powerfull and yet we can sustainably stay for an indefinate period, yours will far exceed mine

My immediate response was, your "low battery" isolator is cutting in, and shutting the system down.

This occurs when the batteries fall below a pre determined level. At that current draw it should not happen, unless you have a really dud battery.

I would check the connections to the battery, looking for a "dry" joint, or bad connection. Basically make sure the battery connections are clean, and make a good contact. These things will do as you have described. I prefer soldered joints as to crimp, as I have seen crimp just to the plastic shieth, and only a couple of strands of wire in contact.

If you are, like I, I would do a isolation test next - just connect the fridge to the battery directly and run it. This isolates all those bits in between.

Batteries are expensive to replace, so make sure it is not the battery to start.

be very cautious about adjusting the low voltage cut out, if you make the batteries go beyond a certain point then they will not "recover", I dont know what this point is, please read all relevent documentation concerning this before you adjust any of the settings

something somewhere is still not adding up to me, you say you have checked ALL wiring

I have left the cut out, seems to be cutting out at about 10.5V. I did the isolation test and both batteries held there charge for 12 hours. Set them up again last night and left on the batteries from about 8.30, checked a couple of times and at 5am the regulator was still showing 12v, then at 7.15 it was down to 10.7v and the poweer had cut out. I checked both batteries at that stage , one was still on 12v the other 10.7v. Seems the second is the problem, but if the wiring is correct then shouldn't it still draw on the stronger??  Seems I will have to get some professional advice and hope I don't get ripped off.

Thanks Dave , and also Dave & Bob. But they both look like new...........Cann't go on looks, I guess that applies to batteries as well.