12v Wiring upgrade for Fridge

technogeekery

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Joined
Apr 27, 2014
Messages
24
Location
Sydney
Car Year
2011
Car Model
Forester
Transmission
M
Hi guys - have read up on this, and think I understand it, but would like to get some more expert opinions.

We are thinking of adding a 3-way fridge to our camping setup. We prefer to find somewhere really remote, and then camp there for 5-10 days at a time, so 3-way is probably the go for us, avoids all the 2nd battery and solar faffing about and expense. Have pretty much settled on a Dometic F400 fridge freezer, which seems to have great reputation for being unkillable and doing what it says on the box.

We don't plan to use it on 12V much, just while we are on the road, but we would like to run it in the car while we are travelling - some of the transport legs are one or two days of 10-hour driving. Like most 3-way fridges, it won't work on the standard cigarette-lighter outlet in the back of the Forester - voltage drop is quite high, and this thing draws 10A+ continuously, and the wiring is not thick enough to cope, apparently. Waeco supply a 12v plug, but you have to get it wired directly to the battery with heavy duty cable.

I'm keen to try this myself, as a 12V learning exercise and to save a bit of money (fridges = exxy). It sounds simple enough - I'll measure it up, but about 6-7m of 8WG cable, get it all routed up through firewall and under trim to back of car. Fit 20A in-line fuse holder & fuse near the battery end, crimp on a couple of ring connectors on the battery end, an anderson plug on the other end, and then make up a short cable with a bit of excess 8WG with an Anderson on one side, and the Waeco connector on the other, as the fridge connector.

Anything else? Any traps for young players? Do I need to build in some kind of auto-sensing switch (relay?) to turn the fridge off when the car is off? I'd like to do that if I could, as it will kill the car dead in a couple of hours if I leave it running in the car by mistake - so any suggestions of what type of relay is appropriate?

Thanks :-)
 
Gidday TG

Looks like a nice unit ... Seems to be dramatic price variation from different suppliers!

I bought the GasMate 35L. It draws about 6 amps at 12 V (72W). Perhaps not so high powered, but kinder to the electrics! $293 at a Repco sale ...

Not sure about your model, but mine is fused at 15 amps for the front socket, and 20 amps (total) for the centre and rear sockets. I would assume that the wiring is sufficiently robust to allow the current draw of the fusing! The front socket is on a separate circuit from the centre and rear, the latter both being on the same 20A circuit.

Be careful not to get confused between L/H drive and R/H drive vehicles. LHD are fused at 15 amps for the centre and rear socket circuit. RHD are fused at 20 amps. Weird??

Section 12-8 of my Owner's Manual.
You should check what your OM says about your model.

I also intend to run mine on the 12V in the car, but on gas when camped. Apparently, no evaporative fridges run all that well on 12V.

Mine will take the cabinet temp down to around -2 to -4°C on 240V. GasMate recommend running it on 240V for at least 24 hours before using it on 12V. They also recommend putting frozen or chilled food/drinks into it, not warm.

I also bought a cheapie secondary battery from Jaycar for $169. Have seen these as low as $159. I will use this to run LED camp lights, and charge all the bits of gear.
 
havachat - thanks for that - yes, I'd seen that, and got a lot of good hints from it.

Ratbag - thanks for your comments. I had a look at the Gasmate and Aldi 3-way fridges too as the price is exceptional. A friend has the Aldi one (very similar if not identical to the gasmate - suspect made in same factory) and gets acceptable performance out of it on 240V and gas, with careful management / pre-cooling / not adding much warm stuff to it. He doesn't run it on the 12V at all as he melted his cigarette-lighter plug...

We've chosen the Waeco / Dometic F400 as it can operate as a freezer as well, and gets another 10-15 degrees lower than ambient than the Aldi fridge. Also great reputation and local support. You are right about the price variance - RRP is over $1000, you can find deals online for about $750 - but Waeco have factory seconds with warranty (cosmetic issues only) for $550 at the moment, which brings it in reach.

Given his experience (not uncommon according to various forums) and the explicit warning from Waeco on the product not to run it on the car 12V cigarette lighter socket, I'm not going to take the chance, but will wire up as above. I found what I need is a voltage sensitive relay, which will shut down the power when the start battery voltage drops (ie ignition off). Total kit from Projecta and others about $100.
 
Gidday TG

I don't really have a need to keep a Barramundi frozen from Darwin to Perth, via Brisbane ... :poke: :lol: :rotfl:.

Kerosene fridges (which is what the 3 way fridges are, essentially) work on the heat exchange principle rather than using a compressor. This makes them much more efficient in some ways, but harder to run really cold on 12V. The current draw is just too high. Thus the necessity for pre-cooling of both fridge and food/drinks on 240V before setting off with the fridge running on 12V.

The cigarette lighter socket on most cars is rated for about 5 amps for about 60 seconds. That's how long it takes for the cigarette lighter to heat up and 'pop'. Even though I gave up the dreaded fags in 1982, I can still remember precisely about this ... Once an addict, always an addict ... :puke: . That's probably why your mate's disgraced itself.

I suspect that this is why the GasMate is limited to 72W (6A) when running on 12V. It draws 90W on 240V. After removing at least 20% for 'overheads' (constant, not dependent on power source; therefore 20% of the 240V draw), this means that the fridge has cooling from 72W on 12V and (72-18) = 54W when running on 12V - i.e. about 75% of the grunt in practice. This is vs a theoretical 80%. Still not enough to work properly, and the power loss is higher when running on 12V as the amperage is higher ... :(.

However, when running on gas, the efficiency should theoretically be even better than when running on 240V, as the gas is burned at high temperature. Heat exchangers work best at high temperature differentials ...

The MY06 OM states that one should never draw more than 120W from any of the accessory 12V power outlets - i.e. 10 amps TOTAL for each outlet. Exceeding this current draw by even a small amount dramatically increases the heat produced in the socket. Since H is proportional to the square of the current, at 10A there is 100 units of heat produced; at 12A, this rises to 144 units; at 14A, it is 196 units, etc.

However, having said that, the centre console and rear power outlets (in the MY06) are already on their own dedicated 20A circuit, and the front outlet is on a 15A circuit with the external mirror motors ...

I plan to run all the "iThings" (as Scooby2 calls them ... :)) from the front socket when driving, and from my auxiliary battery pack when stationary (It has a 2A rated USB outlet). It will also power my camp lights when I get them set up.

The auxiliary battery pack charges from the car battery like any other appliance in the car with its own 2A charger. One can also charge it from 240V, and from solar panels, but I don't think this latter will be necessary for me and my use. It sits on the rear P/S floor, and will be plugged into the centre console outlet.

The fridge will sit on the back seat (of necessity - it's too big to fit anywhere else) and run from the rear cargo bay socket.

I do plan to wire up my trailer plug with a 12V supply straight off the car battery. As you are planning to do, I will run a separate heavy gauge circuit for this, fused at the battery end. This will terminate in my front tool box on the trailer on a standard cigarette lighter socket (female; metal, not plastic ... ).

I will run another lead from the front tool box into the trailer bed. This will have a male end in the tool box.

This will enable me to put my auxiliary battery in there to charge while driving (if I want/need to), then swap the leads over when camped to run the camping stuff from it.

It will also allow me to plug in a jumper from the car battery to the trailer 12V circuit, if necessary.

I reckon that this gives me a cheap and simple solution to power on the move and stopped. It should suit me, as I don't really need anything fancy ... :iconwink:.
 
With my somewhat limited knowledge........a VSR e.g. Matson will cut in and out depending on the voltage level of the battery and is really meant for charging a second battery. For your use (without an aux battery), I would wire it up similar to driving lights, i.e. a normally off relay that activates when the car is switched on. This way your fridge is permanently powered while the car is running. Most fridges monitor voltage and will stop if the voltage is too low, if using a VSR which will cut in & out while the car is running and the fridge also cuts in & out, I'm not sure what will happen!
 
With 8awg, use a 50amp circuit breaker as close to the batt as possible (fuse for the wire size not the load). Run a pos and neg 8awg from the bat to the rear of the car and onto a 50amp anderson plug to make sure there is no earthing issues (beauty of this is you can also use it for trailer/caravan power or a portable compressor). On the batt make sure you use the correct size crimps and crimp it properly



^ you can make it look pretty by putting it in a box, I'd just solder and shrink wrap over the relay, and cut off the fridge lead and solder it on as well. You can use 16awg for this side of the hookup without any problems or the lead the fridge came with, put and inline 20amp fuse to the fridge(unless the fridge is individually fuses as it should be, but double isn't a bad thing as long as the fuse housing and fuse is good quality and has a low/significant resistance), 10amp in the accessory plug will be plenty.

That way you don't need to cut up and of the stock wiring and using the rear 12v port that's already there the relay with turn off the fridge with the ignition. Then you can just take it all out with the fridge and don't need to buy anything special or expensive to do the switching.

Voltage drop shouldn't be an issue with 8awg, (about 2% @10amp over 6m with the engine running)

EDIT: excuse my terrible spelling
 
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Also depending on how paranoid you are, run the 8awg on the opposite side to the fuel lines...just in case. I found the shortest route from batt to boot in my foz meant running the wire with the fuel lines, I'd rather not set myself on fire if I'm hit from the side.
 
Gidday Id

Thanks.

Now, would you really mind putting in all the bits you have left out so that us d'heads can actually do this ... :iconwink: :lol: :rotfl:.

TIA, mate

** BTW, I do understand how much effort is involved in trying to make up complete instructions - I still haven't done it for my Oricom install ... Sorry, I've had flu or a cold for the last couple of weeks.

Still trying to organise all the medical aspects of my proposed trip away! Dentist and Vet complete; two of about five doctors now organised - only three to go ... Copying of printout of medical history, referrals and script renewals now done (almost ... :(). Now just need to reschedule the rest of the appointments that occur while I'm away ...
 
Let me try and put it in English - you run a pair of cables (with the active circuit breaker / fuse protected) from the front battery to the rear cargo space and attach an Anderson plug (this is not in the diagram). In the diagram - you attach a cig lighter male plug to the relay as shown. Attach positives from the relay to the fridge to a matching Anderson plug as shown. Attach negative directly from the fridge to the Anderson plug as shown. Now, with the fridge in the car, plug the Anderson plugs together; plug the cig lighter male plug into the rear cig outlet. When you turn the car on, the accessories circuit will activate the cig plug which in turn will active the relay and switch power on for the fridge directly from the battery. When you turn the car off, the relay will deactivate and cut power to the fridge.
 
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That's just too clever for words, Id & Kevin!

The poweron/off to the male cigarette plug that's plugged into the rear socket (or a double outlet) controls the relay. Flaming smart!

From my Batphone
 
Thanks for translating Kevin, I don't always translate whats in my head to words very well

Ratbag said:
Gidday Id

Thanks.

Now, would you really mind putting in all the bits you have left out so that us d'heads can actually do this ... :iconwink: :lol: :rotfl:.

TIA, mate
Click to expand...


Maybe :cool:, I was taking a couple of photos for my rear 12v install (which stalled because it's been raining) but I haven't taken photos to cover it all. The 8awg in my foz has already been run as i did it with the sub wiring in one go. there's a handy cable trap running along the inside of the sill that the carpet is clipped to in the SF, but most modernish cars have a similar. My setup is a little different as I'm putting a 100amp isolator switch in the rear as well. The panel still needs some some putty to clean it up and another few coats of plastidip. Mighty ditch the crappy voltage gauge as well, it was just out of one of those jump starter packs i picket up at a recycling center for $5. Good way to get SLA batteries cheap lol, but take a multimeter most of them are rooted, You only get 1 or 2 jumps with those packs before ruining the battery as they aren't designed for cranking



I like simple solutions sometimes, the dual bat install in my old toyota was a 3 position 200amp marine switch and a couple lengths of 4g welding wire. Cost me $20 and a drive to the farm, with the alternator voltage sensor moved to the supply line before the switch i could just switch each battery to charge and see the state of charge on the dash voltage. Made jump starting easy to if one didn't work flick the switch, if that didn't work it was some swearing to myself and a roll start :lol:
 
Folks,

This all seems to be a bit too complicated and I think has the issue of large diameter live wires running around the car.

The way I did it in the better half’s car - no accessory plug in the boot?

Run large diameter wire to the boot - put your preferred socket on the end.

Under the hood connect the negative strait to the battery.

Make a sort lead with a 30A fuse connect one end to the battery and the other end to a 40A relay (the switched terminal) Connect the positive cable that is running to the boot to the other switched terminal. You now have the wire to the back of the car fused and relay so if the cable gets munched the circuit is protected.

Now we need to be able to switch the relay - open up the fuse box and find the ignition fuse fit a wire tapped fuse connected to the coil of the relay - make a 2nd short lead and connected from the other terminal to the coil to earth.

Now when the ignition is on - we have power in the boot.
 
^

That's better way to do it for accessory power only. Cheaper as well since the diameter of wire would be smaller. only criticism I've got there is to make a permanent connection and not use a piggyback fuse. But that's more a personal preference.
 
idw, that sounds like a really neat solution - I get the full power solution in the back, together with ignition switched relay, without having to alter the stock setup - nice.

As it turns out, the camp kitchen goddess vetoed the 3-way fridge - gasmate style too small, and big Chescold RC1180 too ugly / not enough control of temperature, apparently. So we bought a compressor fridge instead - a 62 litre Evakool (they were having a special on seconds, it has some surface scratches, but looks & works great and at $460 it was a bargain), which runs very happily off the stock accessory port while we are moving. So I won't end up needing this - but a neat thread for someone else who might.

No, now I need to work out the most cost effective way to power this fridge for up to 10 days remotely! Have filled my head with all the possible solutions, but sounds like at least a 120A/hr battery in the trailer with about 140W of solar panels, a decent regulator wired in near the battery, and that 12v wiring from the alternator carried through to the trailer. Plus a 240v charger for keeping it in good nick at home (although might just maintain on the solar initially). Pretty exxy (about $1000 on top of the fridge itself, I think) way of keeping the beers cold - but I've learned that if the chef is happy when camping, we are all happy...
 
I have a 60L Evakool (white fibreglass) and 2 x 100 AH batteries which were coupled to a 120W folding panel via a CTEK 250S dual DC-DC charger. Could go probably 4 days as a freezer. (I also have a 60L Evakool ice box) I now also have a new 110L Evakool (again the white version), same batteries but now use 2 x 100W panels mounted on my roof top camper; it has not been on a trip as yet.
 
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