Running a 12V fridge from 240V supply?

[Andrew Instone-Cowie]

Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

Why? The two "usual" options seem to be to get a 240V fridge and run it
off an inverter when not connected to the shoreline; or run the 12V
fridge of batteries but leave the charger switched on.

I suspect that the former would take more out of the batteries when
running off the inverter than would a straight 12V fridge. In other
words, it would be less efficient at times when power is at a premium.

If I ran the fridge from batteries and left the charger running, should
the mains fail for any length of time then the fridge would flatten the
batteries to the point at which the low voltage cutout cuts out, andthe
charger surge when the power came back on would almost certainly trip
the shoreline breaker. Losing whatever is in the fridge would be the
lesser of two evils compared with seriously flattened batteries.

So is there such a gizmo?

Andrew

[Gibbo]

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?
Why? The two "usual" options seem to be to get a 240V fridge and run it
off an inverter when not connected to the shoreline; or run the 12V
fridge of batteries but leave the charger switched on.
I suspect that the former would take more out of the batteries when
running off the inverter than would a straight 12V fridge. In other
words, it would be less efficient at times when power is at a premium.
If I ran the fridge from batteries and left the charger running, should
the mains fail for any length of time then the fridge would flatten the
batteries to the point at which the low voltage cutout cuts out, andthe
charger surge when the power came back on would almost certainly trip
the shoreline breaker. Losing whatever is in the fridge would be the
lesser of two evils compared with seriously flattened batteries.
So is there such a gizmo?
Andrew

The early Batts dual voltage fridges were a 12 volt fridge with a 230
volt to 12 volt DC power supply for running from 230 volts.

There's nothing wrong with your approach. I suspect if you have a look
round ebay you'd find plenty of suitable power supplies going cheap.

Look at the rating of your fridge and work out what current you need.
Then allow about 7 times that for the start up surge. The PSU only
needs to provide that for a split second to fire up the compressor.

A quick glance at ebay found this which would probably do.

http://cgi.ebay.co.uk/Switching-Power-Supply-Ham-CB-Radio-10-AMP-13-8-VOLT_W0QQitemZ330000304334QQihZ014QQcategoryZ48708QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Gibbo

[ditchcrawler]

Post by Gibbo

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

There's nothing wrong with your approach. I suspect if you have a look
round ebay you'd find plenty of suitable power supplies going cheap.
Look at the rating of your fridge and work out what current you need.
Then allow about 7 times that for the start up surge. The PSU only
needs to provide that for a split second to fire up the compressor.

snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

[Andrew Instone-Cowie]

Post by ditchcrawler

Post by Gibbo

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

There's nothing wrong with your approach. I suspect if you have a look
round ebay you'd find plenty of suitable power supplies going cheap.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

That looks like it might be just the job!

Thanks
Andrew

[Uncle Marvo]

Post by ditchcrawler
snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

That scares me. Because something says "boat" or "marine" means, normally,
that its price is made for the job, not the kit.

JMHO

[Gibbo]

Post by Uncle Marvo

Post by ditchcrawler
snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

That scares me. Because something says "boat" or "marine" means, normally,
that its price is made for the job, not the kit.

Yeah, I was a bit confused why he seemed more interested in the one at
80 quid rather than the one at 15 quid. Maybe if we sent him a sticker
saying "Marine" he could stick it on the one on ebay and feel better?

:-)

Gibbo

[Uncle Marvo]

Post by Gibbo

Post by Uncle Marvo

Post by ditchcrawler
snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A
transformer, bridge rectifier and a bit of smoothing (caps) is all
you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

That scares me. Because something says "boat" or "marine" means,
normally, that its price is made for the job, not the kit.

Yeah, I was a bit confused why he seemed more interested in the one at
80 quid rather than the one at 15 quid. Maybe if we sent him a sticker
saying "Marine" he could stick it on the one on ebay and feel better?
:-)

Good idea. I have a similar system on the motorbike (probably bored you with
it before).

I am having some "Lucas" stickers made up too, they prolong battery life :-)

BTW, if anyone wants any electronic bits and pieces I almost certainly have
them, worth asking. They'll be free apart from P&P, I just can't bear to
throw them away. There are circuit diagrams all over t'internet for useful
things you can make even cheaper than you can buy them from eBay. There's
about a cwt of junk in my office, all for the taking.

No, I haven't got a ready-made cutout that works at 14v. Yes, I have got the
bits to make one.

[Andrew Instone-Cowie]

Post by Gibbo

Post by Uncle Marvo

Post by ditchcrawler
snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

That scares me. Because something says "boat" or "marine" means, normally,
that its price is made for the job, not the kit.

Yeah, I was a bit confused why he seemed more interested in the one at
80 quid rather than the one at 15 quid. Maybe if we sent him a sticker
saying "Marine" he could stick it on the one on ebay and feel better?

Assuming I'm the "he", cos the former will (probably) fit behind the
fridge, the latter won't. Because the former has a degree of automated
switchover that the latter would involve me mucking about with 240V relays.

I agree about the price though :-(

But then again my idea of a leisure activity involves leaving a large
piece of steel outside in all weathers half immersed in water, and
trying to stop it going rusty, which probably suggests a money/sense
ratio somewhat greater than 1.

Andrew

Post by Gibbo
:-)
Gibbo

[Andrew Instone-Cowie]

Post by ditchcrawler

Post by Gibbo

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

There's nothing wrong with your approach. I suspect if you have a look
round ebay you'd find plenty of suitable power supplies going cheap.
Look at the rating of your fridge and work out what current you need.
Then allow about 7 times that for the start up surge. The PSU only
needs to provide that for a split second to fire up the compressor.

snip

Post by Gibbo
Or you could roll your own. Nothing celever is needed. A transformer,
bridge rectifier and a bit of smoothing (caps) is all you'd need.

Or one made for the job at
http://www.boatfridge.com/index.asp?display=main&productID=44&Col_Category=Power+Converters+AC%2FDC

In case anyone is interested, I asked them whether it was suitable for

Post by ditchcrawler
If it says DANFOSS BD3F or BD2.5F 12 Volt then our unit won't be suitable.
If it says DANFOSS BD35F 12/24 Volt then our unit will be suitable.

Andrew

[ditchcrawler]

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

Just been to Lidl and they have a 13 volt 5 amp supply for £9, I would have
thought that would run a 12v fridge with ease. 13a mains plug one end and
cigarette lighter type socket the other

[Uncle Marvo]

Post by ditchcrawler

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some
sort of power supply adapter from a 240V shoreline?

Just been to Lidl and they have a 13 volt 5 amp supply for £9, I
would have thought that would run a 12v fridge with ease. 13a mains
plug one end and cigarette lighter type socket the other

[awaits comments from Electrickery Merchants before dashing off to Lidl.
That would make a most handy extra beer fridge, under the bed, and there's
always fridges on freecycle]

[Gibbo]

Post by ditchcrawler

Post by Andrew Instone-Cowie
Would it be a feasible proposition to run a 12V fridge via some sort of
power supply adapter from a 240V shoreline?

Just been to Lidl and they have a 13 volt 5 amp supply for £9, I would have
thought that would run a 12v fridge with ease. 13a mains plug one end and
cigarette lighter type socket the other

5 amps will run a normal 12 volt fridge once it's running.

I see 2 possible problems:-

1. "5 amps" may in actual fact be 5 "Oriental amps". They seem to be
somewhat smaller than our "European amps".

2. If it's just a transformer and rectifier, then it will probably
handle the start up surge. If it's a clever regulated supply then it may
not.

Only way to be sure is to try one.

At that price I think it's cheap enough to try.