Last addition to this - just because it was rather entertaining. We used this set up (20W panel, charger with relay cutout added, 50aH LiFePO4 battery, decent 9 litre 12V fridge) while camping over the last few days. We set up last Friday morning and packed up yesterday (Weds) afternoon. Without a word of a lie, the battery ran out of juice at the moment I was disconnecting it all yesterday! A fine example that sometimes we achieve engineering excellence through brilliance, and sometimes there's a hefty dose of pure dumb luck!!! 

I will try to pick up a slightly bigger panel if I trip over one somewhere; contrary to my expectations this setup was pretty much self sustaining in full sun (excess charge in the day balancing out the night), but in typical UK camping conditions - as we had this week - it would be nice to have a bit more oomph so it can last a week.

Cheers,

Andy

if its a peltier fridge they generally use about 5 amps at 12 volts (depening on the module) , maybe your solar is better than you think  or the fridge uses less power, you would only expect 10 hours on battery alone

Hi , no it's a proper compressor fridge so much more efficient: draws 2.2A but only intermittently. I tested the setup before we left (when we had a couple of really sunny days) and it pretty much averaged no power drain from the battery over 24 hours. I was getting between 0.5 and 1 amp into the battery from the panel, depending on the angle of the sun. While we were camping it would have been much less most of the time as it was either overcast or only intermittently sunny.

On battery alone it would last 2-3 days with the fridge set to 4 degrees C provided it was cooled down first (again I'd tested that beforehand - having bought all the parts of course we then had several days of rain, but at least it gave me a chance to try that out). 

Not an advert, there are other makes available which I know are as good (my daughter is an arctic researcher who uses various makes and models to carry her frozen samples!), but this is it: https://carfridge.alpicool.com/products/alpicool-c9pt Goes down to -20C if you want, it's a whole different league to the peltier effect boxes.

I'd tried with our peltier effect coolbox a couple of years ago and that just lead to some very overheated and unpleasant milk and margarine...

Hi , no it's a proper compressor fridge so much more efficient: draws 2.2A but only intermittently. I tested the setup before we left (when we had a couple of really sunny days) and it pretty much averaged no power drain from the battery over 24 hours. I was getting between 0.5 and 1 amp into the battery from the panel, depending on the angle of the sun. While we were camping it would have been much less most of the time as it was either overcast or only intermittently sunny.

On battery alone it would last 2-3 days with the fridge set to 4 degrees C provided it was cooled down first (again I'd tested that beforehand - having bought all the parts of course we then had several days of rain, but at least it gave me a chance to try that out). 

Not an advert, there are other makes available which I know are as good (my daughter is an arctic researcher who uses various makes and models to carry her frozen samples!), but this is it: https://carfridge.alpicool.com/products/alpicool-c9pt Goes down to -20C if you want, it's a whole different league to the peltier effect boxes.

I'd tried with our peltier effect coolbox a couple of years ago and that just lead to some very overheated and unpleasant milk and margarine...