powering up the portable freezer

Submitted: Saturday, Feb 09, 2008 at 10:20
ThreadID: 54385 Views:2946 Replies:10 FollowUps:12
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hi, we are looking at buying a portable freezer, I'm guessing around the 31 to 50 litre size. we were looking at a waeco then the chescold and now the evakool seems to be the best on what I've read up. my question is what sized deepcycle battery and solar panel would you say we would need, the evakool seems to have the less battery drain than the others. we are looking for something that will keep the freezer powered up for around a week of 'bush type camping'. we intend on only using it only as a freezer so it wont be opened all the time, properly only once a day. also do you think that the price of the extra battery and solar panel would workout cheaper in the longrun than filling a gas bottle every month if we got a 3 way freezer?
our intentions are to travel around this great country and to bush camp most time with staying in a caravan park around once a week or so, when possible.
thanks for your help which I'm sure i will get going by my previous experiences Chris.
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Reply By: Notso - Saturday, Feb 09, 2008 at 11:54

Saturday, Feb 09, 2008 at 11:54
I've had an evakool for 8 years now and it has been excellent.

I did an exercise a bit like what you want a while back and was going to buy 2 X 80 watt panels. Currently have a Sealed lead Acid 100 AH battery but can't afford the panels yet.

I can get about 3 days out of the battery before it needs charging. Even if you do buy the panels there are times when you won't get any sun, or enough sun so would have to be prepared to top up your battery some other way if needed.

I use a cheap genny with a charger at the moment but find I hardly ever use it as I seldom camp up for more than a couple of days without power.
AnswerID: 286518

Reply By: bbuzz - Saturday, Feb 09, 2008 at 13:55

Saturday, Feb 09, 2008 at 13:55
I had a Waeco 45 abd sold it as the battery management and costs of solar were going to be too much. Am organising a 3 way fridge and will camp in the bush using gas. Easier, cheaper and works the same. Have the dual battery in the truck so can keep the temp up while travelling.
AnswerID: 286535

Reply By: Russ n Sue - Saturday, Feb 09, 2008 at 14:26

Saturday, Feb 09, 2008 at 14:26
We are doing what you intend to do right now. We run a 50l Waeco as a fridge and a 40l as a freezer. We have no generator to run as backup. The last couple of months have been a good test for our setup as we have been at NE NSW and SE Queensland while all of this this rain has been falling.

We run two 123W Sharp solar panels and 300A/H of storage. Under sunny conditions we can run the fridges and a couple of 12V fans, lights and two laptops day in and day out. Generally our State of Charge of our batteries drops by about 18% overnight. This means that we could run the two fridges and not much else for about three days without any sun. (I don't want to discharge more than 50% as the wear and tear on the batteries is too great.)

What I've found is that even on cloudy days we get some current out of the panels. It varies but often as not, over the whole day we at least make enough power to cover the freezer operation. The end result is that once only did the state of charge of the batteries drop to my arbitrary cutoff point. We then got a couple of good days where there was plenty of sun and our solar regulator went into Boost mode and we got back to 100% capacity.

Worst case is that I could charge the batteries with the vehicle but we never got to the stage where I thought I should do it. If you are like us and will being travelling Oz in such a way that you will hopefully have good weather most of the time, then a setup like ours could be OK for you.

The catch: we are going to be travelling indefinitely, so we though that the expense was justified when spread over a long time. If you only intend to travel for a year or so, it might be a lot of dough that you'll outlay and then either have to sit on the goods or try and sell later to recoup.

To give you an idea, the two solar panels were about a grand each. The regulator was $300.00, the batteries are AGM and were nearly $500.00 for the lot. We purchased a three-stage battery charger for when we do have mains power available and it was all-but $500.00 as well. I also used very heavy cables for everything - the largest size that would fit into 50Amp Anderson plugs for the solar panels and even heavier for connecting the batteries together and to the solar regulator. You could buy a lot of gas with that kind of money.

The benefits of doing it our way are that we have no ongoing operating costs and we don't need to carry a generator, fuel, oil, spares etc. Solar is also totally quiet. The drawback is the initial outlay. You would not have to go to the extremes that we did but from experience I know that you would need at least two 80W panels and to be safe, at least two 100A/H batteries. Remember that the more deeply you discharge batteries, the shorter their life expectancy becomes. I'm aiming the get about seven years out of ours by limiting the depth of discharge to no more than 20%. You can't avoid buying a solar regulator but there are cheaper ones than the one we got.

It's up to you but at least you have a case-study now to give you a starting point.


AnswerID: 286537

Reply By: gonebush SA - Saturday, Feb 09, 2008 at 15:06

Saturday, Feb 09, 2008 at 15:06
hi again, while we are on the subject when joining up the deep cycle batteries do they have to be the same amps? as we have already got a 40a/h and wondered if we can buy say an 80 a/h and connect them together.
thanks a lot for the import so far it's certainly food for thought and now getting our brain thinking of the 3 way again.
thanks again Chris.
AnswerID: 286544

Follow Up By: Russ n Sue - Sunday, Feb 10, 2008 at 11:11

Sunday, Feb 10, 2008 at 11:11
Hi gonebush,

there is always a lot of conjecture about this but the short answer is no, it doesn't matter. When batteries discharge, their internal resistance changes. The overall effect is that a battery of smaller storage capacity will change its internal resistance quicker than one of larger capacity. Its ability to deliver current reduces (but doesn't stop) and you get a proportionate amount of current from each battery and their state of discharge stays about the same.

If you know anything about Ohm's Law it is easier to understand.

What you should do is keep the type of battery the same. For example if you already have an AGM battery, be sure to buy an AGM additional battery. You would not add a Calcium battery to an AGM battery for example. This is because they have different charging characteristics and different float voltages.

Just as an aside, we have been travelling for 8 months now and have talked to a lot of people and one thing we have picked up is that gas fridges really struggle once the ambient temperature gets up to the mid thirties. I don't have a gas fridge so I can't back this up with personal experience, but it is a pretty common talking point amongst those who have got them.


FollowupID: 551877

Reply By: Mike Harding - Sunday, Feb 10, 2008 at 11:28

Sunday, Feb 10, 2008 at 11:28
Chescold, green ($1000) or blue ($1300). Unless you are prepared to spend lots of cash on batteries (which wear out and/or fail) and solar panels or are prepared to run a gen for some time each day then 3 way fridges are unbeatable for stays of more than a few days in the one spot.

My blue Chescold is currently sitting at -19C (26C ambient in my garage) and held -12C and better on the 40C+ days we had last month.

Mike Harding
AnswerID: 286669

Follow Up By: Russ n Sue - Sunday, Feb 10, 2008 at 12:21

Sunday, Feb 10, 2008 at 12:21
G'day Mike.

Interesting comments. When we were getting set up to travel I did a lot of research about refrigeration and safe storage of foods. (Nothing worse than being laid up with food poisoning in a tiny camper trailer!)

As I stated in my first submission to this thread, we run a separate fridge and freezer setup. We monitor the temperature of each separately with commercial grade themometers that we got from a food wholesaler. These are the type where the thermocouple is inside the fridge and the digital display is on the outside, so that you don't have to open them to get a reading. We found that the Waeco 50l fridge can maintain about 3 degrees C by having just the second temperature setting selected. The freezer maintains -17 degrees C on its coldest setting but only manages -12 degrees on the setting before that.

This means that the duty cycle of the fridge is pretty low, but the freezer runs almost continuously. We do this because to keep food safe, a fridge should be kept at below 5 degrees and a freezer below -15 degrees. Check out page two of the link safe food storage temperatures for further info.

The guy I used to work with could never get his three way fridge below -15 degrees on gas! Even in mild ambient temperatures.

I am no expert on food safety but I suspect that if you were keeping food in a freezer for a relatively short time, -12 degrees would be quite safe. We store stuff for three to four weeks at a time, so I'm not prepared to take the risk.


FollowupID: 551883

Follow Up By: Mike Harding - Sunday, Feb 10, 2008 at 12:44

Sunday, Feb 10, 2008 at 12:44
Hi Russ

I checked out the food thing and my research indicated that ideally frozen food should be at -18C or better but there is no significant danger of bacterial growth at better than -10C. I suspect you'd be far more likely to encourage growth during poorly controlled defrosting.

>Nothing worse than being laid up with food poisoning in a tiny camper trailer!

Oh yes there is! Being laid up with FP in a swag! :) I believe the culprit was a tin of tuna - newly opened!

>The guy I used to work with could never get his three way
>fridge below -15 degrees on gas!

They need good ventilation (ideally a computer fan above the heat exchanger) and should be kept in the shade. Also note that many temperature measuring devices are inaccurate. There is an easy and very accurate technique to establish 0C and 100C in order to check your thermometer - unfortunately that doesn't mean it will still be accurate at -20C but it's a start:

Thermometer calibration

If one is on the move daily (vehicle charging) or is prepared to go the solar route then a compressor fridge is the better option but otherwise for those of us who stay in remote spots for many days or weeks I'll stick with the 3 way :)

Mike Harding
FollowupID: 551886

Follow Up By: gonebush SA - Sunday, Feb 10, 2008 at 13:03

Sunday, Feb 10, 2008 at 13:03
hi, those temp reading that you gave out with your fridge- was that running on gas or 240? our experiences with 3 way fridges in the past is that they seemed to get the coldest on gas. we have a 3 way fridge (not a freezer) and when the temp got around 40plus we put a small desk fan at the back of it and nearly froze the drinks. on our caravan fridge we already have a computer fan hooked up to a small solar panel so that it gets the benefits of the fan when it's hot.
thanks Chris
FollowupID: 551891

Follow Up By: Mike Harding - Sunday, Feb 10, 2008 at 13:19

Sunday, Feb 10, 2008 at 13:19
Hi Chris


During our January hot spell (40C+ for quite a few days) the fridge (blue Chescold) was running on 240V in my garage (acts as a beer fridge). Like you I have always thought they always did better on gas (I'm sure my elderly Finch did) so I switched it over to gas for a couple of days but the temperature was the same as 240V. I did have two small computer fans sitting on the top of the vent to help it along on both gas and 240V.

Mike Harding
FollowupID: 551897

Follow Up By: gonebush SA - Sunday, Feb 10, 2008 at 13:29

Sunday, Feb 10, 2008 at 13:29
hi, just a thought, you said that you have 2 small comp. fans on the top of the vents, from all our mucking around and what we have been told the fans work a lot more efficient if they are the bottom or the side to blow cooler air past it instead of the hot air back over it because the heat rises.
FollowupID: 551902

Follow Up By: Russ n Sue - Sunday, Feb 10, 2008 at 13:36

Sunday, Feb 10, 2008 at 13:36
G'day again Mike,

thanks for the info re: calibration. I had them tested at the lab at the company I last worked at and they were accurate back then (within one degree over the entire working range). Also I swap them over periodically and see if they cross-check and so far they've been reading the same.

I'm not sure whether to thank you for the news about the tuna though - I eat a fair bit of the stuff.

I'm sure you are quite correct about the thawing. We thaw in the fridge and if room does not permit, at least in an esky bag. We often commence cooking stuff before it is thawed completely and just allow extra cooking time.

We also tend not to eat frozen seafood products, preferring to catch our own or go without.

It's a tricky business staying healthy on the road!


FollowupID: 551904

Follow Up By: Mike Harding - Sunday, Feb 10, 2008 at 13:37

Sunday, Feb 10, 2008 at 13:37
I'm sure you're correct about the positioning of the fans, it's simply that I haven't gotten around to fitting the properly. I did have them in "suck mode" (so to speak :) though so they were pulling air through the heat exchanger.

Mike Harding
FollowupID: 551905

Follow Up By: Mike Harding - Sunday, Feb 10, 2008 at 13:48

Sunday, Feb 10, 2008 at 13:48
Hi Russ

>It's a tricky business staying healthy on the road!

As you say; thawing in the fridge is ideal - but you do have to remember to start it about 24 hours before you want to eat.

I think the major issue is simply keeping normal good kitchen hygiene standards (as you would at home): hand washing, uncooked food separate from cooked, don't cross contaminate with knives, chopping boards etc.

I've recently started to take some plain A4 paper with me - you might well ask why!? Washing up a chopping board which has had raw chicken cut upon it is very hard and I'm unconvinced the temperature of the washing water or the detergent will kill the bacteria properly. Before starting to chop the chook I place a piece of paper over the board and that keeps much of the chook deposits off the board - subsequently burn the paper and the board is much easier to wash up. It doesn't totally solve the problem but it helps.

Mike Harding
FollowupID: 551913

Reply By: gonebush SA - Sunday, Feb 10, 2008 at 13:43

Sunday, Feb 10, 2008 at 13:43
hi again, I've done a bit of checking up in previous post about the chescold and kept seeing that they can run for around a month on a 9kg gas bottle the today i found a few that said they last 2 weeks and 2 days as there is quite a difference can anyone tell me how long a 9 kg gas bottle lasts using as a freezer.
thanks again Chris.
AnswerID: 286690

Reply By: Mainey (wa) - Sunday, Feb 10, 2008 at 13:56

Sunday, Feb 10, 2008 at 13:56
first things first... the FRIDGE
Best "performance" results come from a fridge with full length and full width cooling plate area, this will cool down much quicker than a smaller plate which is set in one end or one side and end only because the refrigerant is cooling the entire area at the same time, not from just one end or side.

Solar and Batteries
You need to know the total Amps you will use in a 24 hr day.

I don't have to guess at the size and capacity for Solar panels and Batteries, as I use 2 x 100+ ah AGM batteries and 200+ Watt Solar system, the battery system * never * gets below 12 Volts running a fridge that draws 8 Amps.

That's a starting point, you will get away with lower capacities if using a fridge with a smaller power draw.

get the best - forget the rest lol

Mainey . . .
AnswerID: 286695

Follow Up By: Shaker - Sunday, Feb 10, 2008 at 15:12

Sunday, Feb 10, 2008 at 15:12
>>>>> Best "performance" results come from a fridge with full length and full width cooling plate area

Doesn't the Engel have a "cooling plate" completely around the inside.

Also nobody has mentioned Autofridge, arguably the best, albeit the most expensive.
FollowupID: 551929

Follow Up By: Mike Harding - Sunday, Feb 10, 2008 at 15:22

Sunday, Feb 10, 2008 at 15:22
Shaker: want to catch up end of Feb/Early March - I'm hoping to be prospecting around the Woods Point area?

Mike Harding
FollowupID: 551933

Follow Up By: Mainey (wa) - Sunday, Feb 10, 2008 at 16:32

Sunday, Feb 10, 2008 at 16:32
I know the ones I have seen don't have :-)
it was only on one side and one end, hence the post.

But, I have not looked at the new models.

Mainey . . .
FollowupID: 551951

Reply By: Member - Phil G (SA) - Sunday, Feb 10, 2008 at 22:35

Sunday, Feb 10, 2008 at 22:35
Gday Chris,
Theres plenty of good fridges out there. My view is:
- The only reason to get a 3-way is if you plan on staying camped in the one spot for a week or two at a time, and not be using your vehicle. They are finicky, don't work well in hot South Australian weather, have to be dead level (need spirit level) etc On 12volts they will use a minimum of 10amps per hour.

- You left Engel off your list, but I use two of them - sometimes one as a freezer, but mostly use them as 2 fridges (since I bought my own vacuum packing machine). I monitor the temp inside each, and like the way the Engels are so well regulated - you have infinite adjustment of the temperature, so the one with meat gets set to exactly 2 degrees, while the one I use as a cooler gets set to 5-8 degrees. If I use one as a freezer, it sits on about -18degrees. I have used it as a freezer in desert country in 45 degree heat and it kept freezing at about -8degrees. Snowys have the 40l Engels on special at $1050 for the 40litre with inbuilt temp gauge. Max power consumption is 2.5 amps per hour. Any compressor fridge will use heaps less power than a chescold 3way.
AnswerID: 286813

Reply By: meandet - Monday, Feb 11, 2008 at 09:21

Monday, Feb 11, 2008 at 09:21
G'day Chris

I don't know about your circumstances but do you need a freezer at all? We go to Cape Leveque each year for a month and stay in a beach shelter without power. We get a fair bit of meat cryovaced in Broome before we go up and sometimes there is some left when we get back and still ok. There is only 2 of us to cater for. We use a 40 litre Engel, dual battery 50 amp hr and 2 x 40 watt solar panels. We never run out of power and can have a couple of cold beers and a bottle of bubbly each day.

You should look at the Engels also before you make your decision on a fridge. Most people we encounter seem to be abandoning other brands and most now have Engels in the back. One particularly irate gentleman at C L had two units of one of the brands you have mentioned and both broke down. It was good for us because he was a good fisherman and had to give his catch away each day. Another guy, also at CL couldn't beleive how much longer he could get out of his battery when he replaced his same brand fridge which broke down with an Engel.

I know there is a lot of hoo/ha on this forum about fridge brands but my opinion is based on the experience of 6 trips since 2001 and no fridge problems.


AnswerID: 286838

Reply By: gonebush SA - Monday, Feb 11, 2008 at 15:08

Monday, Feb 11, 2008 at 15:08
hi again, we did think about an Engel but in searching out advice on all the different fridges we were told by someone that has a great deal of knowledge not to go near a new Engel with a 20 foot barge pole but if lucky enough to find on older one to grab it and never let go. the reason for this is now they seem to be made with less insulation and that not to leave the cover on to long because of condention is causing them to rust out, ie- one was returned less than 12 months old and totally rusted out. I'm not going to say who this was that told us but they had no reason to lie or stretch the truth, but as I'm sure you can understand it's a lot of money to us and we are trying very hard to get it right the first time, hence all the questions- experience is worth it's weight in gold.
and to answer do we need a freezer, well we are planning to do quite a lot of travelling and this would allow us to stockup were suitable, we have bought a vacuum sealer (not quite as good as cryovacing i know) but it still helps aswell as saving heaps of room.
AnswerID: 286886

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