PLUGGING IN A 12 VOLT FRIDGE

[norsey]

My portable fridge can run off a 12v battery and I need to attach it to the cigarette lighter on the car. My problem is that I have a suitable plug to attach to the fridge but There is no indication on the socket about + and-.
If I connect it the wrong way round will it damage the fridge? If so, do you know how I can find out which is the + pin and which is the - pin on the frige socket?

Thanks

 

[bernardgreen]

If so, do you know how I can find out which is the + pin and which is the - pin on the frige socket?

Yes I know.... read the instructions and / or user's manual. If you didn't keep it use Google to locate a copy of it.

And also use a voltmeter to check the polarity of the cigar lighter socket in the car. Just in case your car is one of the few that do not have a positive centre pin.

 

[ELZ4742]

on the lead, is the plug on the fridge side symetrical? i.e can it be plugged in either way round?( mine uses a stereo '8' type) if so, it doesnt matter which is the + and which is the -

 

[ericmark]

There are two types of 12v fridges one uses gas and an element and it would not matter if either way around and the other uses a French invention and a semi conductor and swapping + and - allows one to warm or cool items and often there is an option to connect either way around according to if food is to be kept cool or hot. One was called Sunny-Cool.
Some because of fans can only be used one way around but with most no harm would be done getting it wrong.
Most cars are negative earth so centre of cig lighter is Positive. Very old cars were negative earth then it was realised the spark works better going from hot negative to cold positive so the were swapped so old cars are positive earth. Then it was realised this caused more rust and it was possible to have a positive earth for spark plugs but still a negative earth for rest of electrics. This was all before days of alternator. Although some early alternators were produced for old cars today all cars use negative earth as hard to find alternators, radios etc. to work with positive earth.
Likely there will be an exception some where but I don't know of any and I would expect all cars from 1980 onwards are negative earth.

 

[Grizzly]

the other uses a French invention and a semi conductor...

A Peltier element: Thermoelectric cooling

 

[IJWS15]

If it is like ours (cold box that will heat) the 12 volt plug will only go in one way round so it does matter.

 

[echoes]

Keep a spare fuse handy for your cig-lighter circuit - I only mention this because a friend set off on a trip of Europe with a sat-nav and a plug-in fridge. The fridge blew the fuse, he couldn't charge his sat-nav and his 'back-up' map was a single side of A4 covering all of western Europe. He got very, very lost in northern Spain...

 

[ban-all-sheds]

As well as losing power to his satnav did he also lose the power of coherent thought, thus rendering himself unable to go and buy a ******* road atlas?

 

[echoes]

As well as losing power to his satnav did he also lose the power of coherent thought, thus rendering himself unable to go and buy a ******* road atlas?

Precise as ever, b-a-s!

 

[ban-all-sheds]

If it is like ours (cold box that will heat) the 12 volt plug will only go in one way round so it does matter.

I've got one of those, and IIRC the power cord is a bit like a C7-PW.

But I do know that for "heat" and "cool" you should really read "will keep warm for a little bit longer than a plain insulated box" and "will keep cool for a little bit longer than a plain insulated box". If you put something cold in it will never heat it, or vice-versa.

 

[ericmark]

Depends on model. In Algeria back in 1980's we had one for snake bit serum. As we stopped working in area where there was a chance of snake bit we re-allocated the unit to keep our bacon in and it kept it frozen solid from fresh as we did not freeze until we got to camp.

However the cheaper units I have used would only cool and not freeze and after the first one I used I was disappointed. Most seem to have unit built into lid and very poor.

 

[ban-all-sheds]

Bacon in Algeria?

That's not very sensitive...

Anyway - what you had was a proper fridge - what I've got, and I'm sure norsey has got, is a UK leisure market powered coolbox.

 

[IJWS15]

As is mine but the plug does not have a square end like your picture, it only has the "cutout" between the pins on one side, the other side is flat.

 

[ban-all-sheds]

I'm just going by vague memory - mine's in the far reaches of the loft as I didn't use it this year - all I know is it's got some sort of polarised plug which I thought had one square end.

Bought the thing in Halfords a few years ago.