12 volt coolbox could it be run off a solar panel....

[Wansworth]

And if so what size of solar panel, thanks.

 

[pcatterall]

Off the top of my head.......no!! you would need a battery of some kind to balance out the input if for no other reason. Those cool boxes use up to 5amps ( mine is around 3.5 amps) With a very small battery ( motor cycle size 20 amps) you would still need a solar panel which would supply the required 5 amps. This would be a large panel. For example my 2 panels have a combined area of around 6 square feet and produce 5 amps but only when the sun is at the optimum position!

 

[VicS]

And if so what size of solar panel, thanks.

Pretty big one. Those Peltier element cool boxes take 4 or 5 amps continuously.

I think you'd need a battery in the system too so that it would keep running at least for part of the night

Its going to be a problem on dull days too.

I reckon about 250 watts

My logic ( very approximate): 5 amps = 60 watts at 12 volts. Probably need to double that for use in UK/ UK weather = 120 watts

that'll give you about 8 hours of operation. Double that to give another 8 hours battery supported = 240 watts ...call it 250.

Going to need a battery of 90 Ah capacity or more and solar panel controller that will also prevent over discharge of the battery.

 

[Wansworth]

thanks...... now the fridge in the yard has been designated communal my cheese needs to be kept in the private sector along with other perishable stuff.

 

[ex-Gladys]

Compressor cool box is the way to go. Mine uses an average of 0.8A per hr. It runs for about 5 mins every 40 min at about 5A. My 2x45W panels easily keep up most of the time, but it's off a 330AH battery bank

 

[PaulRainbow]

My solar panels more or less keep up with a compressor fridge. Depends on how much Sun we get and how much i use on the FM radio, lights and water pump.

 

[PaulRainbow]

My logic ( very approximate): 5 amps = 60 watts at 12 volts. Probably need to double that for use in UK/ UK weather = 120 watts

that'll give you about 8 hours of operation. Double that to give another 8 hours battery supported = 240 watts ...call it 250.

There was an article in one of the YM supplements last year by Nigel Calder, he said :

"I like to work on the relatively conservative assumption that on average I will get the equivalent of four hours of full-rated output a day"

Probably gives a decent rule of thumb for working things out.

EDIT : There's an article by Calder here :

http://www.oceannavigator.com/January-February-2012/The-cost-of-energy-on-boats/

 

[Spuddy]

My boat has a cool box linked to battery via a clever switch that stops current when battery voltage drops below summat I've forgotten. It's only a little box and came with boat so I know no more. Worth trying caravan suppliers. Battery charging is by Rutland wind gen so probably better than solar in UK to keep things topped up

 

[VicS]

There was an article in one of the YM supplements last year by Nigel Calder, he said :

"I like to work on the relatively conservative assumption that on average I will get the equivalent of four hours of full-rated output a day"

Probably gives a decent rule of thumb for working things out.

EDIT : There's an article by Calder here :

http://www.oceannavigator.com/January-February-2012/The-cost-of-energy-on-boats/

Double up on my estimate then! It all works out too expensive.

I reckon the way forward for Wansworth is a good size battery and a charger to match. Recharge the battery each night from the marina shorepower. and start each day with a well cooled coolbox.

 

[PaulRainbow]

Double up on my estimate then! It all works out too expensive.

I reckon the way forward for Wansworth is a good size battery and a charger to match. Recharge the battery each night from the marina shorepower. and start each day with a well cooled coolbox.

Be the cheapest option for sure.

 

[Pete7]

Battery charging is by Rutland wind gen so probably better than solar in UK to keep things topped up

That would depend on a number of things like the size of the solar panel but I am willing to bet pound for pound solar is the way forward in the UK, especially if the majority of use is during the summer.

 

[thesaintlyone]

The trick is to add a mono flexible solar panel connected to your house Leisure battery easy enough and that will trickle charge the house battery make sure you buy a controller with LCD Display which will show you the required info.
Panel prices are not too shocking 100w mono flexible panel on eBay £110 with an LCD controller running at £15.
All connected with Twin core from the chandlery

I only have a small 25w panel on the jouster which keeps me in Cabin lights, Nav Lights, 12v cigarette lighter point for Hand held VHF (charges whilst I'm away) and mobile phone and Nasa Target depth.
Just leave it on the cabin top unfixed.

There is always a big debate on solar and its usefulness/generating capabilities in the UK but the reality is the above set up works for me quite sufficiently for me will probably go for a bigger 100w panel when i get a bigger boat for no reason than I can.

Its all about your consumption

 

[charles_reed]

Short answer - it depends on many factors but unlikely to be feasible in the UK.

Has to be a compressor coolbox, needs a battery in circuit (for the night). My 320 watts of PV @ 39N with an MPPT controller easily keep pace with the box, once it's down to temperature.
My fridge compressor has a start current of 5.5 amps and a run current of 4.0 amps, all @ 12.5v.

Don't know that the theories expounded on the chain are particularly fact-based!!

 

[charles_reed]

That would depend on a number of things like the size of the solar panel but I am willing to bet pound for pound solar is the way forward in the UK, especially if the majority of use is during the summer.

An interesting point - TCO of PV panels is easily the lowest - about 18% per KwH, but the sunlight is the missing factor in the UK. Even in the Med, I'm hard-pressed to find sufficient room on a slightly larger boat than yours to hang an adequate area of panels.
Having said that, the latest generation of panels are about 18% efficient, more than twice that of original monocrystalline.
I'd rule out amorphous panels for anything but temporary, low-power charging.
In UK (and the Aegean) a balanced mix of wind and solar power is probably the optimum answer. Say 300-500watts of solar and a 300watt wind generator. That would allow use of fridge and laptop. Those two are 80% of total, anchored, use on my boat.

 

[Spi D]

Also consider the type of battery as it is going to be drained completely (or until voltage limiter kicks in), which only few batteries will tolerate over time.

Charge after deep discharge takes a loong time so will challenge the equation further.

 

[AngusMcDoon]

And if so what size of solar panel, thanks.

If you go small you can do it despite what the naysayers here say.

I have a compressor coolbox. It's a CF18 - only 18 litres capacity. In the not steamy Scottish climate it uses about 500 mA averaged over a day. I try to open it only 3 times a day. It's set to 4 degrees C. I mostly put already cooled items in it - I'm not trying to chill down loads of beer for example.

To power it I have 2 30W Spectraflex amorphous panels which do better in grey weather than crystalline, connected through a controller to 140 Ah of batteries. My engine charging is only from an outboard so that doesn't provide much. My coolbox runs continuously. I have not been connected to shore power for 5 weeks now. My battery voltage drops to about 12.7 overnight but climbs back to 13.7 during a grey day or to the 14 V controller cut off point if the sun shines.

I'm at 58 degrees north. The comment about it not being feasible unless you are in the Med is not true. At northern latitudes although the solar power available is less the air temperature is much lower so a fridge has much less to do. A normal daytime max here is about 16 C.

Although it works my installation is not cheap. The 2 panels, the coolbox, battery & controller cost about £1k, although of course most of that powers more than just the fridge.

 

[VicS]

If you go small you can do it despite what the naysayers here say.

I have a compressor coolbox. It's a CF18 - only 18 litres capacity. In the not steamy Scottish climate it uses about 500 mA averaged over a day. I try to open it only 3 times a day. It's set to 4 degrees C. I mostly put already cooled items in it - I'm not trying to chill down loads of beer for example.

To power it I have 2 30W Spectraflex amorphous panels which do better in grey weather than crystalline, connected through a controller to 140 Ah of batteries. My engine charging is only from an outboard so that doesn't provide much. My coolbox runs continuously. I have not been connected to shore power for 5 weeks now. My battery voltage drops to about 12.7 overnight but climbs back to 13.7 during a grey day or to the 14 V controller cut off point if the sun shines.

I'm at 58 degrees north. The comment about it not being feasible unless you are in the Med is not true. At northern latitudes although the solar power available is less the air temperature is much lower so a fridge has much less to do. A normal daytime max here is about 16 C.

Although it works my installation is not cheap. The 2 panels, the coolbox, battery & controller cost about £1k, although of course most of that powers more than just the fridge.

Agreed a small compressor type of cooler such as the Waeco Coolfreeze range makes the idea a practical proposition.

 

[ghostlymoron]

Don't forget that, in the UK , you don't really need much cooling overnight provided it's cold at sunset and you don't open the lid too much, the contents will remain cool till morning. Even in the south of France , we found we could turn the Waeco off overnight without it warming up much. (The reason for this was that the noise of the thermostat switching over kept the occupant of the aft cabin awake)

 

[Sailingsaves]

My boat has a cool box linked to battery via a clever switch that stops current when battery voltage drops below summat I've forgotten. It's only a little box and came with boat so I know no more. Worth trying caravan suppliers. Battery charging is by Rutland wind gen so probably better than solar in UK to keep things topped up

clever switch = VSR - the orange one is good. Stops the leisure battery draining the cranker; or can be configured to do a few other things.
https://www.google.co.uk/search?q=S...69i57j69i59.6498j0j7&sourceid=chrome&ie=UTF-8

 

[William_H]

Firstly as said your peltier type cool box is not worth trying to run on solar. They are just too inefficient.
A compressor type fridge is the way to go. The Waeco small fridges seem to be able to run on 12 or 24v battery automatically selecting supply voltage. Unfortunately mine has an auto selected low voltage cut out so it will stop draining a battery. This is good but can't be selected off. It seems to me the fridge should be able to run straight off a solar panel whose voltage might vary from 20 volts down to perhaps 12v. But the under voltage cut out would stop it.
So one would need a buck regulator that will handle the 3 or 4 amps giving 13v from a 80 or 100 w panel if you want to run it without a battery.
You would probably need to run the fridge as a freezer to get it cold for the overnight and certainly my CF18 would need more insulation.
So yes it could be done without a battery but for most of us a battery is the more convenient way to go for boating or camping as we then have a supply for lights etc. olewill