Whats needed to run a 12 Volt fridge?

[Brett]

I'm about to buy a 12 volt compressor fridge but I'm not too sure what if anything I need to do to power it.

I've got the standard 2 battery 12/24V starting arrangement in my 80. Can I connect the fridge to the Power supply JB under the bonnet or do I need to add in a third battery/wiring/split charge relay etc?

 

[Gav Peter]

The quest came with a cigarette lighter fitting - bam, straight in there...

Didn't stay cold like but...

Which one are you going for Brett?

 

[Chris]

OK, the obvious answer is of course 12v. But if you run it directly from one of your main batteries the danger is that you can flatten one of them so that you can't start the vehicle - yes? That's why most go with a third independent battery. Now, if it's a good fridge, it should come with a voltage sensing system that shuts the fridge off if the supply drops to - say 11v so that you can still crank your motor. I would not want to go directly without some kind of protection. You could fit a simple voltage sensing relay in there somewhere if your fridge doesn't have that already.

So you don't HAVE to have a third battery, but you do need protection. There are devices out there I know. Someone will have a link I am sure.

Chris

 

[Brett]

Which one are you going for Brett?

Probably the Kampa 55 litre job.

OK, the obvious answer is of course 12v. But if you run it directly from one of your main batteries the danger is that you can flatten one of them so that you can't start the vehicle - yes? That's why most go with a third independent battery. Now, if it's a good fridge, it should come with a voltage sensing system that shuts the fridge off if the supply drops to - say 11v so that you can still crank your motor. I would not want to go directly without some kind of protection. You could fit a simple voltage sensing relay in there somewhere if your fridge doesn't have that already.

So you don't HAVE to have a third battery, but you do need protection. There are devices out there I know. Someone will have a link I am sure.

Chris

What I was thinking though Chris, is it overkill to run a third battery to power something that's only pulling a load of approx 2.5A/hr?

With a third battery you've then got to charge it (additional load on the alternator) I was hoping I could run some suitable cabling from the power outlet jb under the bonnet to the boot & add in a connector for the fridge?

 

[Chris]

Sorry Brett - thought I'd been clear. No, you don't need a third battery, but if you don't you can flatten you starting battery and be stuck somewhere. So, you either get a fridge with built in protection to stop it flattening your battery OR you fit a separate device in line to protect your battery. The JB under the bonnet is powered from your starting battery and doesn't have any protection in it to prevent too much power being drained out of your battery. It's fine saying that the fridge doesn't drain much, but it still drains and if it develops a fault it could flatten your starting battery overnight



That make sense?


Chris

 

[Jon Wildsmith]

It depends a bit on how you will use the fridge e.g. you might only ever have it on while you're driving plus very short periods with the engine off in which case your standard batteries are fine. If you're going to park up for longer periods especially during the day time (say 8 hours plus) then the existing batteries might struggle to cope with running the fridge at a high enough voltage to avoid its low voltage detection tripping in. Also if your batteries are getting on a bit / not in tip top condition, they may be doing fine just for starter duties but be not very good with a more constant drain on them. Providing your fridge has a low voltage cut out there's no reason you couldn't experiment though and see how it goes?

 

[Gav Peter]

Pack a coule of sets of jump leads too!!!

 

[Lorin]

So you don't HAVE to have a third battery, but you do need protection. There are devices out there I know. Someone will have a link I am sure.

Yep, here's one http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWAX:IT

Should be perfect for what you need Brett

 

[ignat]

Looks like the Kampa 55 Litre already has "Battery discharge protection "

Not sure how it operates comapred to the Waeco:

Battery protection is built into all of our compressor fridges. The fridge is not allowed to run lower than 10.4 volts because most common lead acid batteries in cars can be seriously damaged or destroyed by allowing them to become completely flat or completely discharge, not to mention the extreme inconvenience caused by not being able to start your car! Also, if the supply voltage from the battery becomes too low, electronics and motors tend to overheat. This occurs with all electronics and all motors no matter who the manufacturer is. And that is why we do not allow this to happen to WAECO products.

Basically, in most situations you should run your fridge on the LOW setting - this will allow your battery to run down to 10.4 volts then the fridge will cut out. On HIGH, the fridge will drain your battery to 11.7 volts then shut off. Therefore your fridge will run for longer on the low setting.

 

[Jon Wildsmith]

Don't set it on LOW if you're using the starter batteries, that's much too low to still start the engine, put it on high and expect it to only run for a fairly short time without the engine running. The size of cable you use to power it will have an effect on this as well with thinner cable having greater voltage drop which the electronics will see as a lower battery voltage.

 

[Brett]

Thanks for all the replies chaps, definitely clearer on the electrical side now

Although, I've bought the Kampa 55 this afternoon, I've had it running off the mains charger & it gets lovely & cold very quickly but, the buttons on the control panel don't work So it's going to have to go back.

Shame as it seems reasonably well made but this has put me off. I guess the Engels & Waecos are more expensive for a reason.

Oh well, another case of if something seems too good to be true it usually is