Technical (a bit) battery/fridge question

[pelissima]

impressed

Ah! my air-cooled one runs (at 38Cambient) 20% of the time - takes 4.5amps on start-up and 2.2 amps running.

Always said air-cooling was more efficient ;-)

2.2 amps running,... Ouaouuuuu

Pls give as much details is possible on this.
Mine uses a BD35 and a very old electronic board drawing 4.something, at startup even more.
fair winds
george

 

[Chris_Robb]

Well guys - all my frailties regarding anything of a practical nature are now well exposed - I went the arts route in school !

The manual went to some length to explain how to hang the door from the right or left hand side but does not go into details like power consumption (to be fair it ignores it in a very wide variety of European languages)

I got the 3.8 whatevers from a verbal enquiry but obviously bloomered it up.

The 'fridge is a Engel SRBD and makes short work of an 85AH battery. Current (ha !) practice is only to run it when the engine is running but that is far from satisfactory. Seems a shame to get a generator just to keep a few esentials cool though.

1 - a front opening fridge is not the way to go, - all the cold air falls out every time it is opened.
2. Standard fridges come with 2 inches of insulation, which is the main problem, Its just not enough. Ideally 4 inches alround. We get away with 3 inches on 2 sides and 4 on all the others. We have 2 by 85 watt solar panels which just keep pace when running as a fridge, the fridge draws nearly 7 amps (at 12 volts) and will if wanted run as a freezer at -20deg.

3. Cooling of the compressor - air cooling requires a large volume of air to be available - normally inside the cabin which makes things even hotter.


In short - there is no alternative to a well insulated fridge - top opening, that is if you don't want to charge everyday. Longest I have been without charging was 1 week and at the end the batteries were almost fully charged.

 

[affinite]

Just a thought but ...

Is there any way to convert an air cooled compressor to water cooled without replacing it completely?
Vyv - Ive toyed with the idea of replacing my air cooled compressor with a water cooled one like yours but I was wondering if there was a way of simply pumping sea water around the air cooling fins so that the air would be cooled before entering the rad ?

 

[Heckler]

Is there any way to convert an air cooled compressor to water cooled without replacing it completely?
Vyv - Ive toyed with the idea of replacing my air cooled compressor with a water cooled one like yours but I was wondering if there was a way of simply pumping sea water around the air cooling fins so that the air would be cooled before entering the rad ?

If you are pretty good with your hands and can evacuate and charge a fridge system then whats wrong with making an external heat exchanger? Years ago I had a converted ships lifeboat with a Meadows petrol engine in, all it had as a cooler was a piece of 3/4" copper pipe run along side the keel externally, about 9 feet of it. It got rid of the heat from the engine no prob.
Basically some 3/8" copper tube, made up as an intercooler, you do the research for optimal size! Drill thru your hull, place outside, then connect the existing pipes that go to the condenser, evacuate and refill and away you go, no need for a pump a la vyv cox.
Stu

 

[charles_reed]

2.2 amps running,... Ouaouuuuu

Pls give as much details is possible on this.
Mine uses a BD35 and a very old electronic board drawing 4.something, at startup even more.
fair winds
george

Standard ASU unit with the fan unit replaced by a 100mm 4 watt computer unit.

The secret is keeping the lid airtight - I use a towel.

 

[BigART]

I have a 'fridge that plays heck with my batteries espcially on hot days (natch'). It has a consumption of 3.8w.
I have found a solar panel that claims an output of 8w. I know that this is a maximum but there seems a good margin, and 'fridge current requirement should rise with solar output.
This just leaves the battery to cope with the overnight running when no-one is opening the door to remove beers etc. and, hopefully, the compressor will be running less.

Am I clutching at straws ?

Assuming you mean 3.8 amps, yes, you will struggle with a 8 watt panel.

Think in terms of about ten times that size and you would be closer. We have 180 watts of panel and that keeps up with 24 hour running. In northern climes with low sun angles, and a grey day or two, even this does not suffice. A good wind generator will help as they can work 24 hrs a day instead of the 8 hrs that any sun might be at a high enough angle. Sorry about the bad news. :-(

 

[whiteoaks7]

Fridges

Maybe you need to dodge the question of sourcing amps and look instead at the mechanics: (a) how much insulation there is around the fridge and if you have space add more - much much more - don't have space have insulation! (b) are you getting the heat away from the fridge - if the condensor can't get rid of the heat the fridge will just keep on whirring. Add a computer fan maybe (PBO carried my article on this a while ago but the essence is just get rid of the heat by feeding the condensor with cold air and blowing the hot air outside the boat). If you have perfect insulation and perfect cooling of the condensor you can run your fridge on a very few watts. If you improve these two factors you'll probably find you are better off leaving it run at night.

Cheers, Dave Berry

 

[Loggo]

Thanks Dave Berry - I need to start with working out how the warm air is removed from the area of the fridge. I am not with the boat at the moment but I'm damned if I can remember any vent.