This is a question mainly for Whenarewethere, as I believe you have a smaller portable 2 way fridge/freezer. As I have only ( and only needed this up till now), an 38ah Gel battery, what size Gel battery( it is the only type I wish to use) would I need to run a 2 way  25 lt F/Freezer and  average size of portable solar panels?. Currently have an 80 watt portable quality panel of 12 years vintage.  I currently use a 3 way Portable Finch fridge of 08' vintage, and it works pretty well except in summer on 240volt, as it is currently being used in the house now for xmas. It warms up inside if I put room temps food in it, and takes at least 3 hours to get back down to  2 degrees, to boost it I have to put ice bricks in it. It is rare that we camp in the warmer months so the 3 way works okay for us generally. In warmer months on gas it is quite cold, so not the same problem as on 240. Any advice welcomed and thanked..........  APOLOGIES THIS POST SHOULD HAVE BEEN PUT INTO TECHINICAL SECTION

Have a read of this thread, to the bottom of the page. You will see the energy & time involved cooling 10kg of water.

https://thegreynomads.activeboard.com/t65059593/extra-fridge-insulation-wattage-test/

80 watts or solaR is enough for the fridge. More solaR allows you to charge batteries up quicker.

I would double the 38AH, then you have more leeway with inclement weather. I use Gel batteries, started with 2 x 26AH which was ok, added a third battery for more reserves. Then added a fourth battery. The fourth battery wasn't really necessary, but it just provides more flexibility. We don't bother using the solaR panels for 4 days. 

I have 120 watts of solaR, it's more than we need, but again, it allows a bit speedier charging. Together with top quality wiring we are not wasting any resources.

Insulate the fridge, get a cover for it & a grey foam sleeping mat for Macpac, to look the part. Cut it up & stuff around the fridge inside the cover.

Adding extra insulation effectively is no weight & you in effect are adding battery capacity.

I have the 28L Waeco which is now replaced by a 25L unit. 

I'm taking home made ice to the relatives tomorrow & will fire it up first thing tomorrow morning at -18°C or less -22°C. I have had it down to -25°C according to other thermometers. The little fridge works far better than our Westinghouse home fridge, for a given volume.

You could stick an additional computer fan on the outside for better cooling.

These fridges can do about 48°C below ambient. Put it in a cooler place in the house so it works better & a bit quicker.

A the end of the day it is all common sense. Start with additional insulation on the fridge. Also under it so the cold doesn't drop out of it.

The Waeco fridge lid is apparently hollow. I want to fill it but haven't got around to it. Just another one of those little sub projects to push the limits of efficiency.

If you have any questions please ask.

This is a 2 year old 22L Brass Monkey fridge used in my car over a 9hr trip. Was set a 0DegC & set on Economy. So far Im happy with it.

Still using the Waeco 28L model. It was the only fridge that fitted height & length, had to remove the handle so the boot closed. Height is a whisker tight with the cover.

I stuck the thermometer on the coldest part of the evaporator panel. I'm pretty happy with -26.8°C with an ambient temperature of 27.6°C. The home made ice cream was nice!

I wouldn't be surprised if all these fridges used the same guts & put their own case around it, badge engineering, & some may add a few features.

We mostly sleep in the back, fridge sits on passenger seat & everything else stuffed up front, seats are moved & tilted forward, 1.85m length to sleep. Use Thermarest mattresses. Works really well. Use window socks for warmer weather ventilation.

Disadvantages: rearrange the car twice a day, 20 minutes each time. If there is too much rainy weather is does get tedious. Two trips we have returned home sooner due to excessive rain. 

An older photo but in principle the arrangement in the back of the car. Up to 80L of water, 8 x 5L in photo.

I am still amazed how much we can pack in the car with careful arrangement, buying products to fit a space, or modify them.

The small fridge loaded with food is just light enough to be moved twice a day.

We live in the city in a Unit that was built in the 1950s, small garage 4.95 long, can only open driver's door to first notch, height clearance 1.86m. Street parking is a disaster, parking permit is required & a trailer permit is $500pa when I looked a few years ago.

This is the 22L Brass Monkey i have, they are simmilar to every other 12-24V compressor fridge.

Thank you for the internal photos of the Brass Monkey. The condenser is a basic wire condenser with very little surface area.

The Waeco has an aluminium fin condenser which provides a huge surface area for cooling.

I replaced the fridge's 92mm fan with a 120mm fan which has a higher volume of air flow & pressure.

Interesting all the Waeco fridges i have 80L upright, 40L & 50L portables all have this type of condencer with Secop or Danfoss compressors.

This Waeco upright fridge has fins. Saw it in the shops earlier this year.

This is where our 28L sits overnight, we make sure the vents are not blocked.

Well, I may not have to get a brass monkey, went to the tip today, and found an old waeco, of at least 10 years vintage, with plugs and both 240/12 volt. Condition quite good, wasn't thrown, was just sitting there, outside the tip, where people leave stuff, if it is any good. Our tip is unmanned so normally everything gets crushed and shredded. I cleanedt it out. It is about a 30lt size but that section where the label is is worn off. It is currently on 240 volt, and cold sitting at 2 degrees. Haven't tested it on my test 12 volt battery yet, but even if this doesn't work, I should be able to fix it. If it is not worth fixing on 12 volt, if it doesn't work, it will be my shed fridge and my xtra xmas, festivities  fridge. This is just plain luck considering I was going to buy a new fridge early next year. Now all I have to do is win the Lotto on Saturday night, and this week will be complete.