12 volt Fridge - how much power do they use

[Martin Megson]

Hi,

I have a 12 volt "Coolmatic" fridge which is 10 years old and I think is getting past its best. It works but is quite noisy.

It draws a current of around 3.8amps, which does not seem excessive but it is running for around 60% of the time. That is to say it will run for around 12 minutes, switch off for 10 minutes and so the cycle repeats. I'm thinking of replacing it and I see that similar fridges draw around 3 amps but I cannot tell from the specifications what percentage of time a modern fridge runs.

 

Please could anyone give me an idea of the percentage I could expect a fridge to run or alternatively an idea of the daily amp/hr usage.

 

 

[Phil Ambrose]

I have a Shoreline under counter larder fridge which has a 110 litre capacity which averages out at about 40 a/hr per 24 hours, would not be without it.

 

Phil

[mrsmelly]

Having had both 12 and mains voltage they both draw very similar amounts. If plugged in then mains is a no brainer, If not plugged in then for me mains through a good quality inverter is the way I always go.

 

Tim

[Ex- Member]

We have a 240v fridge which according to our amp meter draws just 1 amp when the motor runs. The amp meter seems accurate with regard to other items we've tested.

 

The fridge is A+ rated 117 KWH per year.

 

I reckon that's about 26 amps per day not including inverter which uses 0.2 amps. The fridge hardly runs though so It's a bit of a mystery why it uses so little power. It is always very full though.

[pelicanafloat]

The problem with a mains fridge is the start up current. When fitting out our boat we bought a Liebherr fridge freezer that was perfect until we went off cruising- ie, we actually started using it! The current draw was running at about 5amps, but the start up current could be in excess of 60amps. And we cruised, the battery bank would gradually lose its power, the voltage would drop and this coupled with a massive current demand meant that the start up current would increase. After a few months the batteries were knackered. Now, I'm not saying this applies to other systems, but it did apply in our case.

 

So we looked around and came across these people: Inlander, based in Birmingham.

 

http://www.12v-fridges.com/index.php

 

The danfoss compressor is quiet and for a large fridge freezer the current draw of about 3.5 amps is quite acceptable. Digressing, we have solar panels connected to the batteries and during the summer months they don't need much early morning sun to produce 5-6+amps, and this makes for a very happy lazy start to the day :-)

 

We bought our appliance about 3 years ago and it has been completely hassle free

Edited September 28, 2013 by pelicanafloat

[bottle]

Meggers

 

There are a lot of factors in the percentage running time of a fridge or freezer, ambient temperature, door opening, thermostat setting....

 

Just buy the best rated (A+++) that you can afford and work on 50% run time, it will probably be less than that though.

 

 

An aside,

 

We recently had trouble with our freezer and the only way it would run was to turn on the 'fast freeze' so to cut a long story short, it is now controled by a simple time switch that turns it on for 15 minutes once an hour, works perfectly.

[ditchcrawler]

 

 

We recently had trouble with our freezer and the only way it would run was to turn on the 'fast freeze' so to cut a long story short, it is now controled by a simple time switch that turns it on for 15 minutes once an hour, works perfectly.

I have a LEC mains fridge and cant find the thermostat, I suspect that the knob on that adjusts a timer of some description.

[Bro]

I'm sure it's been mentioned before but as fridges are a killer for batteries I'll repeat this tip for good measure:-

1. Keep fridge full as possible (if necessary fill with freezer packs to fill all spaces) to give max. coolable mass store.
2. When running the engine, turn fridge temperature setting to lowest acceptable level. Alternator will supply the power rather than batteries.
3. When engine is stopped, turn temperature setting to highest acceptable level. The large mass of cold store will take much longer to rise to the now higher temp setting than would otherwise be, thus the motor should be much delayed in cutting in and battery power is saved.
4. Don't open the fridge door any more than you really need to.

For me, when cruising, adopting this method of working made a significant difference to battery drain.

 

As an aside. Does anyone have views on the pros and cons of using one or two 12V cooler boxes rather than a pukka fridge in a boat mostly used for short leisure cruising trips (out for 7-14 days say) rather than as live-aboard?

[Ex- Member]

I'm sure it's been mentioned before but as fridges are a killer for batteries I'll repeat this tip for good measure:-

1. Keep fridge full as possible (if necessary fill with freezer packs to fill all spaces) to give max. coolable mass store.
2. When running the engine, turn fridge temperature setting to lowest acceptable level. Alternator will supply the power rather than batteries.
3. When engine is stopped, turn temperature setting to highest acceptable level. The large mass of cold store will take much longer to rise to the now higher temp setting than would otherwise be, thus the motor should be much delayed in cutting in and battery power is saved.
4. Don't open the fridge door any more than you really need to.

For me, when cruising, adopting this method of working made a significant difference to battery drain.

 

As an aside. Does anyone have views on the pros and cons of using one or two 12V cooler boxes rather than a pukka fridge in a boat mostly used for short leisure cruising trips (out for 7-14 days say) rather than as live-aboard?

 

We follow tips 1 to 4 although we also turn the fridge temp down when solar is running as well.

 

The cooler boxes from our experience are very 12v power hungry, especially the ones that have 240v capability too. Can be noisy as well. But for short trips with engine running the issues I mention wouldn't really matter.

[mrsmelly]

Mastervolt inverter. New mains fridge aaa rated......job done.

 

Tim

[trackman]

12V cooler boxes use a different, much less efficient technology than normal fridges. Avoid them like the plague, they will use far more power!

[smileypete]

With a mains fridge off grid, one important thing to bear in mind is inverter standby current.

 

If standby current is say 0.5A then that's up to an extra 50kWh a year!

 

So best have an inverter with a low power standby mode. There's cheap methods of getting round it otherwise, but they're not exactly 'plug and play'...

 

cheers, Pete.

~smpt~

[Taslim]

12V cooler boxes use a different, much less efficient technology than normal fridges. Avoid them like the plague, they will use far more power!

Wot he says but the (peltier effect?) devices have their place.

 

I have a small fridge type in the van and it keeps my drink cool in summer and (reverse the polarity) my pasty warm in winter.

 

It is power hungry so is rigged to only work when the engine is running.

 

I use a gas fridge in the truck but am comming round to #10 (mrsmelly) point of view 'cause the fridge is well efficient and cheaper than a 12 volt and the inverter can be used to do other stuff to.

Edited September 29, 2013 by Taslim

[Martin Megson]

Many thanks for the helpful replies.