Is there an adaptor to run 12v fridge from the mains?

[rubblequeen]

Hi, I have the usual 12v fridge powered by the leisure batteries. I have also the regular power sockets for when I am plugged into the land line in the marina.

There is an inverter for powering the regular sockets from the leisure batteries.

 

When not cruising the fridge quickly lowers the voltage in the batteries. I want to know is there some way of powering the fridge while in the marina from the mains lead.

Hope this makes sense

[David Mack]

Battery charger.

[nicknorman]

You would need a very beefy 12v converter to run the fridge directly from the mains - just for the few moments of startup surge. So as David says, the correct way to do it is simply to use a battery charger. This allows the batteries to supply the momentary peak startup demand and then be recharged by the charger. Use a proper marine or at least a multi-stage charger, not a cheapo car charger which will be unregulated.

[AndrewIC]

Shoreline sell such a thing, but it ain't cheap....

http://www.shoreline-marine.co.uk/spares/electrical-bits/ac-to-dc-power-converter-power-200

[ditchcrawler]

I only have a 4 amp charger but the few times I have had a mains hookup that charging the batteries will more than cope with the fridge running

[MtB]

You would need a very beefy 12v converter to run the fridge directly from the mains - just for the few moments of startup surge. So as David says, the correct way to do it is simply to use a battery charger. This allows the batteries to supply the momentary peak startup demand and then be recharged by the charger. Use a proper marine or at least a multi-stage charger, not a cheapo car charger which will be unregulated.

 

 

I'd have thought a cheapo battery charger connected straight to the fridge terminals (with no battery) would do the job admirably. The peak start up current on 12v fridges is regulated down unlike a 240vac appliance, so I've read on here a number of times over the years.

[Higgs]

Hi, I have the usual 12v fridge powered by the leisure batteries. I have also the regular power sockets for when I am plugged into the land line in the marina.

There is an inverter for powering the regular sockets from the leisure batteries.

 

When not cruising the fridge quickly lowers the voltage in the batteries. I want to know is there some way of powering the fridge while in the marina from the mains lead.

Hope this makes sense

 

 

I've been running my Shoreline 12v fridge from a 650w computer power unit for over two years non-stop. You can find instructions on YouTube, it isn't that difficult to adapt. The CPU runs cool and it caused no problems with the BSS in June. I'll have to check later but it's either a 20amp or 30amp inline spade fuse used. The CPU output is around 35 amps.

 

You have to bundle the 12v wires together. Check out the videos. The CPU is a Tesla, nothing-special unit, cost £26.00.

Edited August 11, 2016 by Higgs

[frangar]

What you need is a waeco MPS-35 rectifier. Works with any danfoss bd-35 compressor powered fridge & auto selects between DC & AC. The output is 24v but the BD35 is fine with that...the lamp in older shorelines might not be tho. They work well.

 

Cheers

 

Gareth

[Tony Brooks]

 

 

I'd have thought a cheapo battery charger connected straight to the fridge terminals (with no battery) would do the job admirably. The peak start up current on 12v fridges is regulated down unlike a 240vac appliance, so I've read on here a number of times over the years.

 

I doubt it given the problems when people do not observe use the recommended size of cable (1 sq mm CSA per metre between battery and fridge). This implies a large volt-drop on start up which in turn implies a large start up current.

 

I go with using a quality multi-stage battery charger to the batteries when on the mains, a 10 amp one would be more than ample and I suspect a 5 amp one would do. This means no alterations to the wiring and the "change over" from mains to 12V is automatic. KIS.

 

Another advantage is that the domestic batteries would be kept close to fully charged so would tend to last longer.

[nicknorman]

Anyway whatever the exact details of the startup current vs charger size, the point is that a battery charger only has to be able to cope with the long term average current drain (including thermostat off time) whereas a device directly connected has to be able to cope with the peak startup demand which is bound to be much more.

[Top cat]

Another solution could be to fit a solar panel to keep your batteries topped up wherever you are. For just the fridge 130W should do it for most of the year, 200W would be better for longer.

Back that up with a good 4 stage mains battery charger, my C Tek 20A unit is more than capable of keeping up with all our demands.

 

Top Cat

[Sea Dog]

As you may be becoming aware, you have a battery charging issue, not one of powering your fridge. Your fridge will be quite happy on your batteries. If you haven't got a decent charger already, you really should have if you want your batteries to last, so it'll be money well spent.

[frangar]

Personally I like the waeco unit...means I can leave the fridge independant of the battery's when I'm on a hook up...leaving rest of 12v off if I'm away....meaning if there's a mains failure I don't come back to a flat battery bank as I would do if running thro a charger.

 

Some people seem to be making this quite complicated when for £50 there is a ready made solution!

 

Cheers

 

Gareth