How much...

[warlock]

12/24v fridge draw in 12 v mode?

 

Hi all,

I know these values can vary, I was just wondering if anyone could give me an average figure. The reaason I ask is because I bought a 12v 5A PSU to run my fridge from the mains with. After 2 months it's been baked and I think it was because I've been over loading it. Before I lash out another 30 bills I wouldn't mind an average current figure so the replacement will be rated high enough.

Cheers, Rob

[chris w]

My 12v fridge draws about 4 to 5 amps on a 50% duty cycle approx. However, I read about some fridges drawing 7 or 8 amps and all fridges will momentarily draw a large current as the motor starts up. I would advise to get at least a 10 amp supply; a 5A power pack will always be marginal.

 

Why not get a new PC power supply from Ebay for around £10-£15. This will be more than adequate for the fridge.

 

Chris

[Tony Brooks]

12/24v fridge draw in 12 v mode?

 

Hi all,

I know these values can vary, I was just wondering if anyone could give me an average figure. The reaason I ask is because I bought a 12v 5A PSU to run my fridge from the mains with. After 2 months it's been baked and I think it was because I've been over loading it. Before I lash out another 30 bills I wouldn't mind an average current figure so the replacement will be rated high enough.

Cheers, Rob

 

 

Danfoss told me to assume about 38 amps upon start up for cable calculations, so if your fridge has a Danfoss compressor you have the answer.

 

Tony Brooks

[DHutch]

Our 24v Engle draws just a shade over 2amps, which for a comparable 12v tallys well with chris's 4-5amps.

 

Computer power supply might do it, but at the same time ive had bad expernce with using them as 12v supplys before now. Although rated at about 20amps down the 12v line i killed one drawing about 6, and had to put a bit of a resistor accross the 5v line to get it to work with that.

 

Maplins do a nice serise of 13.8volt units in 4/6/8/10amps or somthing like that, there 10amp one is about £40, continuosly rated at 7amps, 10amps at 50% duty cycal. and 12amps peak. Very solid units.

 

- Alternativly, shoreline to a box for exactly that for there fridges. Costs £90, but its always an option.

 

 

 

 

Daniel

[stuart]

Why not get a new PC power supply from Ebay for around £10-£15. This will be more than adequate for the fridge.

 

 

Also available for a meagre £6 brand new - http://www.ebuyer.com/UK/product/20083

[Norman Bond]

OK, I'll admit it. I think I am missing something here.

 

12 volt fridge that takes 4-5 amps when running, but anywhere up to 38 amps to start up. What you really need is a way of supplying a steady 5-6 amps and a way of storing some of that excess power so that it can be supplied in a rush when needed. Some type of current reservoir - like a big rechargeable battery.

 

So connect your fridge to a car battery and put a trickle charger on it to keep it topped up.

 

Even better, put the battery away in something like an engine room and join it to the fridge with heavy gauge wiring. Better still have a big bank of batteries all joined together so that there's a massive current reservoir available and stick a small, cheap, efficient trickle charger on them just to replace the fridge current.

 

Damn. Will somebody PLEASE tell me what I am missing. I know there must be something and it is driving me mad trying to work out what it is.

 

 

 

Norman

[SoggyMoggies]

It does seem strange to take 12V from your batteries, via an inverter to get mains voltage, then go through a transformer to get 12V again. One reason is that the 38A will give rise to a pretty big voltage drop over the length of a boat, which means you'll need much heavier wiring. Another is that the battery voltage is liable to vary depending on their state of charge, or whether they are being charged, and the equipment connected to it may not work over the whole range of voltages. It will often be better in practice just to power everything off the mains, even if it is rated at 12V.

[pagan witch]

I may be missing sometheing here too but agree that taking 12v, turning it to 240 then dropping it back down seems daft.

 

Assuming that you have 240 available why mess about at all. Buy a decent mains fridge (about 1/4 the price of 12v jobs) and run it from an inverter if needs be when you have no mains.

 

We run like this with no problem and it has the added bonus of not needing to run BIG cables to avoid voltage drop.

[chris w]

Rob

 

Do you not have a multi-stage mains battery charger? The good makes (eg: Victron, Sterling, Mastervolt) will act as a power supply for all your 12v accessories and will run your fridge with no problem.Which battery charger do you have?

 

Chris

 

Computer power supply might do it, but at the same time ive had bad expernce with using them as 12v supplys before now. Although rated at about 20amps down the 12v line i killed one drawing about 6, and had to put a bit of a resistor accross the 5v line to get it to work with that.

 

Daniel

 

With computer power supplies all lines must be active for the unit to function correctly, ie: you must put about a 10 ohm 10W resistor on the unused 3.3v and 5v rails.

 

Chris

Edited August 12, 2007 by chris w

[warlock]

.....Maplins do a nice serise of 13.8volt units in 4/6/8/10amps or somthing like that, there 10amp one is about £40, continuosly rated at 7amps, 10amps at 50% duty cycal. and 12amps peak. Very solid units.

 

- Alternativly, shoreline to a box for exactly that for there fridges. Costs £90, but its always an option.

Daniel

Cheers for all the info guys, It was one of these units I had, rated at 5 amps, 7 at 50% duty cycle and 10A peak if memory serves me correct. I just don't think it was quite hard enough so I'll get a 10A next time.

I may be missing sometheing here too but agree that taking 12v, turning it to 240 then dropping it back down seems daft.

 

Assuming that you have 240 available why mess about at all. Buy a decent mains fridge (about 1/4 the price of 12v jobs) and run it from an inverter if needs be when you have no mains.

 

We run like this with no problem and it has the added bonus of not needing to run BIG cables to avoid voltage drop.

I'm not..I've a 12v fridge that I'm running from the 240v mains on Colin as I live on him, running the fridge from the batteries empties them in a matter of days and as there's no charging system on board apart from the alternator it's the easiest/cheapest way of having a fridge.

 

Ta muchly, Rob

Edited August 15, 2007 by warlock

[bramley]

mate, i said before, just hook up a battery charger, only small one will do, it will top them up to the neccecerys runs of the mains, like i used to the engine was only started for water,