Thumper Pack

buy a quality battery and put it in an off the shelf marine battery box. ....... AND remember to restrain and ventilate this battery properly.

cheers

What size battery are you aiming for?
A 50litre fridge will use a reasonable amount of current ie, amp hours per day AND night if hot weather. More if used as a freezer.
The solar has to be able to run the duty cycle AND recharge all AH from the night use too OR the battery will go flat.
Warm weather and overcast may see insufficient charge to the battery, so some alternative may be required to keep the fridge /battery charged enough so battery damage doesn't occur. I presume you have a solar regulator for the panels.
A small battery AH capacity may not be sufficient, so rather than a thumper size you may require a THUMPER ie, bigger AH rating. Min 105AH.

That, with good sun and the panels would allow for continual use without battery damage or fridge stopping as a result of low voltage.

The panels will have to be aimed for maximum solar return.

Last time I checked, the Waco draws about 3.5 Amps when running. Multiply by about a 40% duty cycle and you are looking at draining 17 AH over night, very rough figures. That drain will increase during the warmer temps and increased use during the day.

I think the advice on a high quality marine or deep cycle around 100 AH is good advice. I'd be comfortable with the idea that 160 watts out there during the Peak Sun Hours will keep the drinks cold.

Iza

Hi Goldlink,

You know the old saying, "you get what you pay for"!
Sure, a cheap option is to buy a deep cycle battery and stuff it in a marine battery box. But, in reality you won't save all that much. Considerations on isolating this auxiliary battery from the starting battery with an isolator and a means of charging it when traveling need to be taken into consideration.

I can suggest two better alternatives for you to consider.
A Sidewinder Flyer "smart" battery box to which you add a battery of your choice.
The Flyer comes with it's own built-in isolator (optional model) and both Merit and Cigarette sockets to plug your devices into. It includes the correct size wiring cable to connect it to the starter battery. A suitable battery is an AGM style which is the safest to have in the rear of your vehicle.
ABR - Sidewinder Flyer

Another option is the genuine Thumper from the Home of 12 Volt.
These are very practical and again come with a complete charging kit
An 80Ah Thumper is a good size for a 50l fridge and is still portable enough to remove from your vehicle to place closer to your campsite, or use as a jump starter, or portable 12v supply for many other 12v devices. It is a fully sealed, robust solution in one "box".
Home of 12 Volt Thumper

Anything larger than an 80Ah solution, whether in one "packed" box such as the "Thumper", or a separate AGM battery and box such as the "Flyer", will render it virtually non-portable due to excessive weight.

I have a Flyer in the tub of my vehicle with a 100Ah AGM battery in it and it isn't portable. It stays where it is in the front corner, securely fastened down.
I also have my trusty 75Ah+ Thumper which I take on longer trips because it is portable and I use it for a multitude of uses.

Both these options work out about the same price and you would be looking in the order of $700-$900, (depending on size) when all features are taken into account, but you will have a sound auxiliary power source as a result.

Come good deals on what you need here . . .
Home of 12 V sale

Something like this would be perfect, and reasonable price . . .
120 amp/hr package

No association, was just clicking around to get a visual on the Thumper when I found this.

Hi Goldlink

I’ll preface my comment by saying this isn’t an exact science and requires assumptions to be made.

You have indicated that you might be “off-grid” for up to 5-days at a time, so in principal based on “back of the envelope” calculations perhaps something as small as a 50A battery will suffice. But you might want to give some margin and look at 80A.

Power Use

Fridge: 3.5A cycling for a total of 10 hours each 24-hour period in summer (Total 35Ah)

Power Input

2x80W Panels generating 3A each operating at 70% efficiency with a peak solar period of 7 hours in summer (Total 30Ah)

Let’s assume you use a 50A battery to run the fridge and it has a maximum discharge of 50%, giving circa 25A available.

Assume a full SOC at the beginning of a 5-day period.

Battery available: +25A
Solar input: +30A
Power draw: -35A

All things being equal you will have an approximate draw of 5Ah per day and if you have a 50A battery, this should give you up to 5 days “off-grid” before the battery requires an additional source of charging (eg: vehicle alternator or a generator).

Whilst there are a number of other factors that could influence the outcomes, hopefully this gives some guidance.

Cheers, Baz – The Landy

Yes Baz, so many variables.
The panels the OP has might not have output as stated, many ebay / cheaper ones don't.
My 100w folding blanket type puts out 6 amps in full sun, my 150w 9 amps, pretty much a tiny bit over specs they print.

I wouldn't depend on any sort of calculations, all it takes is some cloud and your solar input is halved, my 100w blanket output in heavy dark grey cloud is 2.5 amps, enough to keep up with my Technii fridge no worries, but then would drain overnight a fair bit.
If base camping, you must have over supply of daytime amps in from solar, or greater capacity to hold charge for a number of days use.
Then, the alternator can recharge it when on the move again, hence the link to a suited package as in my above link.

Personally I feel most people would not base camp totally for 5 days and not drive ANYWHERE for that time, even short explores of local tracks etc each day, or duck into town for some supplies, would be enough to greatly reduce the need for either more solar input, or larger battery capacity.

How much all these things relate to the OPs needs is like that proverbial piece of string.

Personally, I wouldn't like to go less than say a 100 amp/hr AGM battery with 160w solar, even if you could cope with half that capacity over say 5 sunny days.

Me, I don't think I've ever camped that long !!
More daily touring moving along to a new place daily.
I never need solar in this situ, but have hooked it up if staying somewhere for a day or three, about my max attention span without going somewhere :)

hi
Reality needs to be adhered to here .
PSH is Peak Sun Hours ,anything else bonus .
Average Australia is 5.5hrs per day of 100 % production of solar
160watt = max output = 9ahr
5.5 hrs x solar production 9ahr
=49.5ahr minus electrical losses etc
49.5 - 20% = 39.6 ahr

losses can be cable size to small ,controller type ,litte cloud etc etc etc

50lt fridge can draw upto 50ahr in a 24hr period
[very hot and opened frequently ups the on time cycle]

In very moderate weather 30ahr /24hr period

At least 160 watt solar
At least 100ahr battery

Goldlink,

Interesting that you haven't commented/thanked any of the respondents, who have gone to some considerable lengths to try and give you advice.

Hoping this was not a troll question.

Thank you to everyone that has assisted with my question, sorry I havent acknowledged the great research and info that has been given, just got home from work. Now to do my homework, looking forward to my impending camping trip hopefully with a cold fridge !

Alternative Thinking
Swampy had some good points and he noted those are average figures for solar, could be less sun = less power. I note that the Thumper systems use traditional lead batteries so get heavy fast. Running batteries down to low voltage significantly reduces their life. Remember lead batteries have to have oversize ratings as the discharge "curve" is basically a straight line from full to minimum voltage, so the rating of 12 v is some where along the middle of that slope.
Perhaps you should look at LiFePO4 batteries as they produce relatively constant voltage from full to minimum charge (most good systems have high/low V protection, same concept as Thumper), just like your portable power tools. They are dry type, chargeable from the truck and weight 1/3 or less of a comparable lead chemistry battery, and a smaller lithium battery equals a lead battery in rating.
Probably kick up a lot of dust with this post!
Hauling unnecessary weight is a no, no - IMHO.