OT - 12v Fridges

Mark Solesbury came up with the following;:

I'd give it a permanent feed ... and I'd have a second leisure battery to feed it from, wired in via a split charge relay so that when I drove anywhere it would get a charge boost, though it ought to last a weekend. Our 12v in the caravan, at only 90 Ah, lasts almost a full week running fridge, lights, and water pump without recharging.

Depends if you want a proper job or just enough for 1 weekends camping!

I personally would use a permenant fused live feed and, as you say, let the fridge thermostat do its work.

However, its what you connect it to that should concern you most.

I have a small coolbox type fridge (which is admittedly cheap and crappy but does the job on a cool-warm day). When running on a warm day it WILL drain the battery quite happily if it is working all day which couldl leave you stranded.

If its just for a one off I would suggest you dont leave it running for any more than 4-6hrs (to be safe and sure your car will start again).

If its for a more permenant solution, as someone else said a second battery and split charge is a must. Having said that, rather than shell out the £££'s for 2nd battery and split charge I swapped my bog standard battery for an Oddyssey PC1700. That will run the fridge all day and night and still start my 200tdi in the morning - perfect for what I need at the moment.

Others may suggest that a heavy relay for a couple of ££ is enough for a split charge system...I'm not too sure about that and hence did not go down that route.

Jon

Jon came up with the following;:

Hmmm ... thinking of doing similar to our 300Tdi, how do you get on with the 'bigger' battery? Is it worth the extra cost?

We only occasionally need the extra oomph of a larger battery, but when we do it's normally also at just a time when we'll also need to be sure we can start the engine the next day .. ;)

If possible plug it into the cigarette lighter. If you cannot, then use an ignition feed. If you leave it on all the time you will soon have a flat battery. When you mean camping are you going to use the 12volt supply on site or is a gas fridge as well? Mick

Battery is great. It has massive CCA's and also the ability to sustain light loads for a long period of time. The Oddyssey is like having an optima red top and yellow top all in one, only it can give a considerable more CCA's than the red top.

I thought long and hard beofre handing over the cash, but am now pleased I did.

Indeed. Isnt it always the same!

On or around Thu, 21 Jul 2005 11:07:13 +0100, "Paul - xxx" enlightened us thusly:

small commercial battery (644 or 645) will fit the 300 TDi, with about 1/4" to spare.

You need to re-route the wiring harness which runs around the end of the battery and you need to attack the battery holding clamp to make it fit. Neither job it difficult.

make sure you get the right battery (can't tell you right now, ours is out) as the wrong one has the terminals the wrong way round and the wires might not reach.

Connect it to a second battery running off a split-charge system, otherwise you risk not being able to start the truck when you come back to it.

Also ISTR that there are different types of batteries, those intended for starting cars which are designed for high current short duration use, and also "Leisure" or "deep discharge" batteries that are designed for medium-current long-duration use. Use of a normal car battery in a deep-discharge pattern apparently damages it, have a search for keywords like "battery deep discharge sulphation" for more info.

Sorry I didnt realise you where considering putting battery in a Disco...Size may well be important, its not such an issue in a Defender.

Austin Shackles came up with the following;:

Heheheh, that'd really piss me off if I did that ... thanks. ;)

Jon came up with the following;:

Cheers Jon, appreciated.

Jon came up with the following;:

Thanks anyway, Jon. No worries, my bro's a welder so we can fit almost anything in anywhere if we need to, IYSWIM .. ;)

to confirm....

It is only a one off weeked, the car is a brand new golf, so the battery/alternator is in good nick (i hope!)

I think i am going to run a live feed with a fuse..... its a new fridge 2, so the thermostat should actually work.....

Thanks for the advice!

Ideally ======= A permanent connection should be to a seperate 'leisure' battery being charged from a split-charger, solar cell or wind generator designed for the purpose.

OK-ish ====== Just connect to the cigarette lighter socket. Remember to unplug when the vehicle is stationary unless you want a flat battery.

Bodge ===== Don't plug it in. Pre-freeze the coolbox by filling it with what you'll be taking then stick it in the deep freeze with the lid off. If the coolbox isn't full then fill the gaps with those freezer ice packs. When at the site, drape a wet towel over the coolbox and keep it in the shade but open to the breeze. Re-wet the towel when it gets nearly dry.

so PDannyD was, like...

That's not a bodge! That's the *traditional* method (apart from the freezer bit). Had a similar system when I was a kid, with a saucer and a large pottery thing to cover a milk bottle. Water in the saucer, refill when dry. Milk never went off, despite not having anything resembling a fridge.

An' yer try to tell the kids these days...

Not to worry you but my car is a new Golf too!! In the boot is a permenant live cigarette socket. I just use that - works fine.

However, beware. Whether its right or wrong I dont know, but the man in the VW garage told me that a Golf battery can only be charged once from flat without any long term damage to the battery. Airing on the side of caution, dont let it flatten the battery!!

Jon

Mark

It depends a lot on what type of fridge it is.

If it's an absorption type; i.e. silent and with no moving mechanical parts, then connected to a 12volt supply, it will draw about 8 to 9 amps continuously. This will flatten your battery quite quickly!

These are really only intended to be operated from 12volts while your engine is running.

If it's a peltier type cooler; i.e. a solid state cooling unit which can also be used as a hot box by reversing the polarity, and is equipped with 1 or 2 small fans, then expect it to draw a current of about 4 to 5 amps continuously. A few of these are fitted with a thermostat(not the cheap ones), and some are fitted with a low voltage cut-out which prevents the cooler from flattening your battery. I would expect one of these thermostatic units to be drawing current for most of the time as they are not very efficient.

The power usage of these is high, but if equipped with a USEFUL low voltage cut-out, could be used connected permanently.

If it's a 12volt compressor type fridge; i.e. just the same operation as your domestic fridge, then using mine(a Waeco CF18) for an example, you could expect it to draw a current of about 4 amps for as little as

The power usage of these is low by comparison and will almost certainly run the longest before shutting down due to low voltage. Hence of the 3, this would most suited to being left permanently connected.

HTH

Neil

(Reply via NG please)

Yes, Neil is right that absorption and peltier element fridges will flatten your battery quite quickly. But even a compressor fridge will, given time. So it would be much safer to only have them life whilst the engine is running, or go for a second battery with split charge.

That doesn't have to be expensive, a normal leisure battery doesn't cost too much and a split charge relay should be around £10, or less.

Pieter

so Neil was, like...

Anyone know if these peltier types are repairable? I have this type of cool box which doesn't seem to work, either cooling or heating. The heat/cool lights go on, and the fan works, but no noticeable change in temperature whichever way round the plug is. It's old now but it insulates well, and I'd like to have a go at fixing it if there is a way, before I chuck it and get another.

You can buy new cells, which are better than the cheap Chinese cells. The cheapies aren't sealed around the edges, letting condensation attack them. The best cells are made by Marlow industries

Use a LITTLE TINY BIT of the white thermal transfer compound stuff on the surfaces of the heatsinks in the fridge wipe off the huge amounts that they use to guarantee the cell will fail after a few months. The amount you use should be barely opaque and very thin.

To really boost performance, you need to lap the heatsinks on very fine emery on a glass plate - I have had 10 degrees more cooling from these fridges with that kind of care.

Steve