Solar panel and fridge

[Amarillo]

I am now convinced that we as a family of four will be able to tour without the need for a roof box, so are now contemplating solar panels to extend time off-grid. Is 100w sufficient for night-time lighting, running a coolbox and charging phones, laptops, etc, or should we be going for 200w?

On a three night trip to Swanage, it became apparent that our old 3 way (12v, 240v & gas) fridge was not appropriate for an extended tour, so we are in the market for an electric (12v & 240v) coolbox. We are looking at the Mobicool U32, at £55 is appears to be excellent value for money. Is there any good reason why we should spend more than twice the money and buy the Mobicool G35?

 

[2into1]

You should spend 7 or 8 times as much and get a compressor fridge, such as a Waeco. The thermoelectric ones you've linked are severely limited in what they can do in hot weather, and burn more juice than the compressor models.
I don't think 100w is enough (if you can do more) although the specialist on here (Roger donahue?) has data suggesting it is.

 

[WelshGas]

I am now convinced that we as a family of four will be able to tour without the need for a roof box, so are now contemplating solar panels to extend time off-grid. Is 100w sufficient for night-time lighting, running a coolbox and charging phones, laptops, etc, or should we be going for 200w?

On a three night trip to Swanage, it became apparent that our old 3 way (12v, 240v & gas) fridge was not appropriate for an extended tour, so we are in the market for an electric (12v & 240v) coolbox. We are looking at the Mobicool U32, at £55 is appears to be excellent value for money. Is there any good reason why we should spend more than twice the money and buy the Mobicool G35?

Are you planning on using the Coolbox outside the vehicle on 240v?

 

[kave]

I would buy as large as you can fit just to be safe.
For 55£ I dont think you get a proper compressor coolbox, the cheap ones sucks battery and are quite ineffective. I bought the Waeco cfx28 which seems to be the best energy wise at the moment.

 

[MattBW]

For me it depends on several things:

1) What kind of fridge you have, I think that make is cheaper because it is an absorption fridge and they aren't very efficient on 12v. Usually these types (same as a three way in a camper) are designed to be on 12v only when driving along. These will run down a battery pretty quick. Probably more reliable on gas if you dont have hookup. Compressor fridge is probably what you need for off grid and to complement a solar panel..

2) What time of year you want to camp, 100w as Roger will probably agree is ok in summer and may result in off grid.

3) Your battery capacity, as SE has good battery capacity, anyway, depending on how long you stay away, you may have enough with the right fridge. If you aren't going for too long a smaller panel may just extend your range enough.

There is a speadsheet on here somewhere that I used to work out the average power consumption of my devices and input my battery capacity to work out how long I could stay off grid.

E.g on my old t25 with my 80w panel, it was off grid indefinitely without a fridge. With my compressor fridge the stay was 3 or 4 days without solar to 5 or 6 with solar (one battery). Cloudy day or poor weather and it quickly declined. This was for a CF40 waeco if I had gone for a CFX28 I would have got a few more days.. I seem to remember I calculated I needed a 120w panel in good weather to not need hookup.

If you want truly off grid, 200w is probably good most of the year round and will give you more than you need in good weather and hopefully that would mean enough in the not so good.

Then there is the matter of fixed or folding. Now fixed is massively convenient, on all the time, doesn't take up space. It is however on your vehicle and sometimes you have to park out of the sun (or its too hot to park in it) However a folding one can be placed in the sun with the van in the shade, it can also be moved to face the sun at an optimal angle meaning its probably working more effficiently than a fixed one.

The downside of a folding or portable panel of course is that it needs storing, can get in the way and is of course insecure. Again having 200w capacity for me could potentially counter some of the downsides of a fixed panel when not in ideal locations.

It's a matter of what is best for you.

 

[MattBW]

I agree with the others however, those fridges will be good on 240v and gas but not really on 12v. 12v should really only be when driving along to keep it cold until you arrive.

 

[Amarillo]

Excellent advice as ever here.

It looks like we'll be going for a 200 watt solar panel fixed to the roof rails and a Waeco CF or CFX fridge.

We will be camping on our year long tour of Europe throughout the year - summer northern Europe, winter southern Europe - typically staying on campsites 1 to 7 nights before moving on. We will also be staying at self catering accommodation, typically 7 to 14 nights at a time where we hope to hook up, and very occasionally we will stay in hotels, usually overnight only.

 

[MattBW]

All those fridges will have detailed power useage stats available, so you can get an idea of what it will use on average. Panels will also have the same stats for power output.

 

[Bramco]

Tom, we spent 6 weeks on a trip to Italy with just a cheap 12V/240V coolbox but then there were just the 2 of us, so beer, wine and whatever else needed cooling. We did this without a solar panel but were mainly on hookup. The great advantage of this type of coolbox is not only the price but with the right size you can fit it in a 2 seat Beach between the passenger seat and the box thingy. We spent a couple of nights wild camping and had no problem with it running down the leisure battery.

It was pretty hot while we were there and the coolbox coped admirably.

Since then we were recently away without hookup and after 2 or 3 days we needed to do a run to charge up the leisure battery. I've since installed 100W of solar so when we're away in the future we should be able to last longer.

I'm guessing you'll be on sites with hookup mostly as you'll also need the other facilities, loos etc. So you could maybe manage with just a coolbox. One thing you might do is to try it for £55. If you decide you need something chunkier you'll be able to buy a Waeco on your travels and probably a lot cheaper on the continent. Just a thought...

 

[Roger Donoghue]

With a coolbox a solar panel ( or two) has no chance of keeping up. You do have to have a compressor fridge. Expensive but vital. There are portable ones for around £350 if you shop around.

Coolboxes run at around 4amps all the time. Compressor fridges run at around 4 amps but only some of the time.

Once you have a compressor fridge a 100W system will keep up with:

Fridge set to medium (much more and you are throwing away a lot of energy on not a lot of difference in temp)
Charging a phone or two
Some music
Lights and water pump
Charging a tablet as long as it's in the day time. (or night time if you have 2 batteries)

This is in good weather. Bright. Some clouds are not a problem but grey gloomy skies are.

Once you add more phones, a laptop, those kind of things, you might want to look at 200W. Bigger systems also cover you better in "mixed" weather

Also the health and capacity of your leisure batteries is important. A dual battery setup with 100W of solar will perform siilarly to a 200W solar system with one battery - in as much as the dual battery system will get you through the nights with ease, then being refilled during the day via solar, and having the capacity to store lots of excess/unused energy ready for the next night, whereas a single battery system is limited by how much the battery can make use of the day time sun. Often a lot of charge is thrown away as the battery gets full by late morning.

Single battery systems are fine mind you. You just have to be a bit more careful at night time - avoiding charging laptops etc until the sun is up!.

 

[Bramco]

Roger,

Great summary but I would question your conclusions a bit.

Our coolbox is a cheapo from Lidl and is rated at 70watts and we have a 100W panel on the roof. This is on a Beach, so no water pump to power and only one battery. Without the solar we'd manage 2 or 3 days without hookup or driving before the leisure battery was running out of steam.

With the panel we can last much longer which is enough for us, we generally move on after a few days. So the driving recharges the leisure battery.

The coolbox suits us as it sits behind the passenger seat in front of the storage box which is very convenient. Rather than a compressor fridge which wouldn't fit there and would have to be in the boot.

Also, I'd question whether the coolbox is drawing a full 4Amps (using your example). Most of these coolboxes have a dial to set the temperature and in the UK at least you don't want to have it set too high as everything freezes up (ours is rated to cool to 20C below ambient). I'll admit it takes a bit of jiggling to get the setting right depending on the temperature but if you have it set at halfway then it won't be drawing the full current.

So while a compressor turns on and off, a coolbox set at halfway will draw power all the time but at a reduced load. Which would make them similar in usage for similar specs. The Waeco coolboxes are rated at 47W about the same as the CF40 which a lot of people have, so it would be good to do a test to prove or disprove my assumption that the coolboxes draw less when set lower.

So personally a £35 coolbox rather than a £350+ Waeco will give us similar performance. £300+ buys a lot of pub lunches!

PS also by charging phones and tablets from the USB on the dash, i.e. the main battery you can reduce your impact on the leisure battery(ies). Phones and tablets don't use very much at all. Now if you want to run a TV etc. then you'll need a portable generator.......

 

[Roger Donoghue]

Trust me, the coolboxes draw much much more than compressor fridges. There is a reason they are £350 + and coolboxes are £35

I have seen numerous customers who have come to me with a dead battery and a coolbox. A normal coolbox (4 amp continuous - they never have a thermostat) will flatten an 85Amp hour battery in about 16 hours at the most. With dual leisure batteries, say 220Ah in total, I'd expect around 2.5 days ish.

Most coolboxes don't come with a dial. Most coolboxes come with an on/off switch.

You can't "freeze everything" in a coolbox unless the ambient temperature outside is less than 17 degrees, because that's the max they can lower the internal temperature. What does happen is the Peltier heat exchanger in the lid starts to form ice (frost up) when left running for too long, and that will freeze items that are touching it.

When these coolboxes are running in the summer they have to work 100% of the time to reach their specified temperature drop of 17 degrees (or approx half the time for 11 degrees - at a guess)

It's great that your coolbox works for you, but a fridge it is not. Your coolbox has the (unusual) feature of an eco mode., where once you turn the dial down, it will take the temperature inside 8 to 11 degrees cooler than outside. If you turn it to "max" it will take it 17 degrees lower than outside, and draw 4 amps continuous. They don't specify what power it uses on eco mode, but it would be fair to assume somewhere a bit over half, lets say 2.5 amps. (this is the spec for the Lidl Rocktrail coolbox)

http://www.lidl-service.com/static/17355662/70350_DE.pdf

If you are happy with moderately cooler items then this is a great way to save money. If you want properly chilled items, and perhaps ice in the ice tray, then you need a compressor fridge. I really have lost count of how many customers I've spoken to who've killed their leisure battery by using a cool box.

They certainly have their applications - it works for you clearly, and I used to use one camping. I'd put blue plastic ice blocks from the camp site freezer in each morning to give it a head start, then run it off my car battery, with a 40w solar panel to help during the day, then turn it off at night (camping in france). The one occasion I forgot to turn it off I hade to use the solar to charge the car battery for an hour to give it enough juice to start... (this would have been a small 75Ah battery in an MX5 - campinng in France)

You can also happily run a TV off leisure batteries with solar.

I certainly would not recommend charging tablets from the starter battery unless you are running the engine every few days. It's a very easy way to get caught out. Tablets use 2 to 3.5 amps for a good few hours.

 

[hirsty]

As you're going to be living in it four-up Tom I agree bite the bullet on both counts - there'll be grey wet day somewhere along the trip when the site shop is shut & you're *so* glad to have charged iPads & cold milk / Sauvignon on tap.