Best way to run a 3 way fridge from a tow vehicle whilst driving.

G'day People,

I have recently purchased a camper trailer that has a 3 way fridge and I would like to run it on 12v whilst driving.

The camper trailer is fitted with a 120 a/h battery with a 7 amp CTEK charger. I also have a CTEK M300 portable charger that is rated to 25 amps.

The trailer has been wired with 2 Anderson plugs with one for the battery and the other dedicated to the fridge.

The 2 options that I have considered are;

1. Install a redarc BCDC 1225-25A DC-DC charger (or similar) in the tow vehicle and power the fridge through the Anderson plug that is already fitted.

2. Install a inverter in the camper and use the portable CTEK M300 to run the fridge.

I believe option 2 would have the advantage of having a inverter and would be a cheaper.

If anybody has any input or other ideas, it would be much appreciated.

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Reply By: Member - Rod N (QLD) - Friday, Mar 13, 2015 at 16:39

Friday, Mar 13, 2015 at 16:39
Has the tow vehicle been wired with 2 Anderson plugs? If so why can't you run things from the two Anderson plugs as is?
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Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 17:02

Friday, Mar 13, 2015 at 17:02
Rod,

I am yet to fit the Anderson plug to the tow vehicle so it's a option to fit 2.

The auto elec who suggested a DC-DC charger believes that even with a isolator fitted to the tow vehicle, the power supply will cut in and out on the new Ford Rangers.

If power from the tow vehicle goes through a DC-DC charger then this power interruption will not be a problem, it will also work as a isolator and charge the battery up to 100%.

Thanks Ben
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Follow Up By: Member - Rod N (QLD) - Friday, Mar 13, 2015 at 17:21

Friday, Mar 13, 2015 at 17:21
If you haven't bought any gear for the Ranger yet, check out Redarc as they have an isolator for vehicles with 'smart' alternators.
Have a look at Redarc Smart Start
I think that is what your auto elec was referring to.
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Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 17:36

Friday, Mar 13, 2015 at 17:36
Thanks Rod, I will check it out.
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Reply By: Member - Bill D - Friday, Mar 13, 2015 at 16:53

Friday, Mar 13, 2015 at 16:53
G'day

This might be opening a can of worms, but I have a mate who runs his 3-way fridge in his caravan ON GAS WHILE DRIVING. He reckons he's been told that this is OK by a caravan expert. What does everyone think of this?

Bill
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Follow Up By: Member - Rod N (QLD) - Friday, Mar 13, 2015 at 17:05

Friday, Mar 13, 2015 at 17:05
I think most vans have a sticker saying to turn the gas off at the bottles when travelling.

In any case I would not want to be in the same servo as him.
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Follow Up By: TomH - Friday, Mar 13, 2015 at 17:40

Friday, Mar 13, 2015 at 17:40
Only an idiot does that.

Ask the guy at Banka Banka a few years ago that put a portable fridge running on gas on the ground and then vented a jerry can.

Lost his whole rig and put his wife in hospital with serious burns.

Also the one who had a gas line break going into eighty mile beach and just got unhooked in time to lose the van but not the car. Is recommended ALL gas taps are turned off at the bottle before commencing travel.
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Follow Up By: TomH - Friday, Mar 13, 2015 at 17:42

Friday, Mar 13, 2015 at 17:42
Definition of an expert

One who learns more and more about less and less and ends up knowing everything about nothing
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Follow Up By: Racey - Friday, Mar 13, 2015 at 18:03

Friday, Mar 13, 2015 at 18:03
Apart from accidents, think about when you pull into a servo you have a naked flame just waiting to ignite those petrol fumes. Definitely a tosser and the so called experts who said it OK are bigger tossers.
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Follow Up By: Bob Y. - Qld - Friday, Mar 13, 2015 at 18:19

Friday, Mar 13, 2015 at 18:19
Thought I had a copy of it somewhere.........



From memory, think they were very lucky there wasn't more serious injury......or worse.

Bob

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Can't remember most of it.

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Follow Up By: Roachie.kadina.sa.au - Friday, Mar 13, 2015 at 18:56

Friday, Mar 13, 2015 at 18:56
G'day Bill D,

Would you mind posting up the number plate of your mate......I will then commit that plate to memory and if I see your mate anywhere near me on the road with his van in tow, I will get the flock-out-a-there!!!

Seriously, the bloke has been given some very dodgy info by the so-called expert. He is sitting on a time bomb!!!

Roachie
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Follow Up By: Frank P (NSW) - Friday, Mar 13, 2015 at 22:42

Friday, Mar 13, 2015 at 22:42
"Definition of an expert"

An "ex" is a has-been and a "spert" is a drip under pressure.
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Reply By: Gronk - Friday, Mar 13, 2015 at 17:04

Friday, Mar 13, 2015 at 17:04
I wouldn't do either !!

Either piggy back both andersons straight to the 4wd anderson and pull the fridge one when you stop driving or do the same but put a vsr in the fridge line.

Why would you want a dc/dc charger powering a fridge ?? or an inverter ??

Keep it simple !!
AnswerID: 549919

Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 17:31

Friday, Mar 13, 2015 at 17:31
If I run a wire ( via a isolator ) to a Anderson plug in a Ford Ranger, I am told that the power supply would be intermittent due to the new alternator design.

The DC-DC charger(apparently) fixes this problem, an isolator would not be required and the van battery would be charged to its capacity.

My understanding is that if a inverter was fitted to the trailer, then a DC- DC charger would NOT be required.
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Reply By: Frank P (NSW) - Friday, Mar 13, 2015 at 17:37

Friday, Mar 13, 2015 at 17:37
Ben,

Looking at the M300 Owners Manual, it appears this charger does not have a supply mode. Therefore it is not suitable to run the fridge unless both are connected to the battery. Additionally, trying to charge a battery with a high-drain appliance like a 3-way fridge (12-15 amps) connected at the same time is not very satisfactory. So installing an inverter to run the M300 is not the way to go in my opinion.

Given the two Andersons on the camper, if I was doing it this is what I would do: I would install an Anderson at the back of the tug, and make or buy an Anderson double adapter to power the two Andersons to your trailer. I think the best way to charge a camper or caravan battery is with a DC-DC charger located in the camper near the target battery. The DC-DC charger can make up for the voltage drop encountered in the long cabling from the alternator and still provide a tailored charge to suit your camper battery.

So one trailer Anderson would power the DC-DC charger. Depending on the output of the DC-DC charger the supply cabling in the trailer for that should be 6mm, but preferably 8 B&S. I assume the other trailer Anderson that goes to the fridge goes directly to the fridge's 12V input.
Check the cabling - it must be AT LEAST 8 B&S (=8AWG, =8 gauge. NOT 8mm). If it is not, then re-wire it.

This is because for the fridge to work on 12V the 12V supply MUST have minimum voltage drop under load and the only way to do that is with big cable. You need 12V or more UNDER LOAD at the fridge. Small cable won't hack it. You need an Anderson at the back of your vehicle. That must be cabled with AT LEAST 6 B&S for the reason stated above - ie to minimise voltage drop in the supply to the fridge. You should also use an isolator of some kind (VSR or ignition-controlled "dumb" solenoid) so that when the engine is off the supply to the camper is off. This will prevent the fridge running your crank battery flat when you go to buy your supplies.

Yes, you could just unplug things, but the first time you forget you will rue the day you decided to skimp. Make up or buy an Anderson double adapter so that you can plug it into the back of the car and have two Anderson outlets.
One will go to the fridge, the other to the rest of the camper and the DC-DC charger. If you make your own Ando double adapter, for practical reasons use 8 B&S (it's only a short cable run, maybe just a few inches, up to you), the 6 is too hard to do tight bends and you won't get two cables into one terminal.
(See the photos to get an idea of what I mean.)

As others have mentioned, you can get Ford to de-activate the Ranger's smart (ie low output) charging system. This would definitely be better for the fridge and would be my recommendation for practicality and simplicity. Also mentioned elsewhere, Redarc make low voltage versions of their DC-DC chargers for vehicles like the Ranger, so you could try an unmodified charging system. If it works, well and good. If it doesn't, get it switched off.

Cheers
FrankP

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Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 18:05

Friday, Mar 13, 2015 at 18:05
To utilise a AC charger then I was thinking option 2, which requires a inverter. Not sure if this is an option??
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Follow Up By: Member - John and Val - Saturday, Mar 14, 2015 at 09:04

Saturday, Mar 14, 2015 at 09:04
Ben,

Frank has covered the subject very well. One thing I'd add - personally I'd run two heavy cables from the engine bay to plugs at the towbar, rather than a single one to be shared by a double adapter. This will cost cable, but minimize losses and so improve performance of both fridge and dc-dc charger.

Unless you have other reasons to carry an inverter I wouldn't have one in the rig. Certainly taking 12V up to 240V and then down again to 12V is a horribly inefficient way of getting back to where you started!

Cheers

John

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Follow Up By: Frank P (NSW) - Saturday, Mar 14, 2015 at 09:11

Saturday, Mar 14, 2015 at 09:11
Thanks, Mods, for the repair work :-). Much appreciated.

Ben,

IMO option 2 is not a goer. I don't think the M300 has a supply mode. It's geared only toward charging a battery, not supplying a load. There are other chargers that DO have a supply mode - one of those might work. But then you can't charge the camper battery AND run it in supply mode at the same time. You COULD if you ran two chargers, one in supply mode driving the fridge, one charging the battery. Getting a bit OTT, I think. Better going the DC-DC charger route, IMO.

Here are the promised photos:





Cheers
FrankP

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Reply By: Slow one - Friday, Mar 13, 2015 at 17:50

Friday, Mar 13, 2015 at 17:50
Ben,
I have a new Ranger and don't have any off the bits mentioned.

First thing I did is have the alternator smart charge turned off by Ford. They do this for free. Then get your heavy duty wiring installed for the anderson plug and when you pull up just pull the plug out so the fridge doesn't flatten your start battery. I then just change it over to gas.

That is all I have and all works well with no expensive chargers or relays.

One thing I won't do is ever run a fridge on gas while driving.
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Follow Up By: Gronk - Sunday, Mar 15, 2015 at 15:35

Sunday, Mar 15, 2015 at 15:35
As I mentioned earlier.....the KISS method...simple and cheap !!
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Reply By: HKB Electronics - Friday, Mar 13, 2015 at 17:50

Friday, Mar 13, 2015 at 17:50
I believe the smart charge function in the Ford ranger can be turned off by the dealer, if you get this done then you could go with a simple VSR setup if you prefer.

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Follow Up By: HKB Electronics - Friday, Mar 13, 2015 at 17:51

Friday, Mar 13, 2015 at 17:51
Slow one was faster in this case:)

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Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 18:13

Friday, Mar 13, 2015 at 18:13
Thanks HKB,

If running a VSR setup, would the camper battery be able to be fully charged to the same level as a DC-DC charger?
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Follow Up By: HKB Electronics - Friday, Mar 13, 2015 at 19:37

Friday, Mar 13, 2015 at 19:37
You should have no problem charging the batteries as long as suitable cabling is installed, I would also keep the fridge on its own circuit as already wired so that it doesn't affect the battery charging. Some would argue that you don't need to if adequate cabling is installed but then they are talking "large" diameter cable.

Keep in mind if you decide to go a DCDC charger that you still need to install adequate to meet both the supply needs of the charger and the fridge.

If your only needing the 12V to keep the fridge cool during traveling, in a finch I had, I just used the normal 12V supply from the trailer plug to power the fridge during traveling and had a separate circuit (6B&S) via Anderson plug to charge the camper battery, it worked fine.

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Reply By: Sand Man (SA) - Friday, Mar 13, 2015 at 18:47

Friday, Mar 13, 2015 at 18:47
Ben,

Bearing in mind that a 3 way fridge draws in the order of 12 amps or more, the 12 volt setting should only be used when the engine is running and switched through the ignition circuit to ensure that there is no current draw from both the vehicle battery, or the one in the camper.
When parked up for a shortish time, the fridge will maintain the temperature as the door is not being opened.

Running the fridge on 12 volts from the camper battery will do nothing but destroy the battery in a short time, and using an inverter for a current draw as large as this, doesn't make sense. Don't even consider running the fridge from a 12 volt supply for any length of time. If stopped for a prolonged period, switch the fridge over to gas. This is the most efficient for this kind of fridge, unless you have an external 240v supply.

My best recommendation is to sell the three way fridge and invest in an upright compressor fridge. These are much more efficient and much more effective in warmer climates.

Bill


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Follow Up By: Ben M10 - Friday, Mar 13, 2015 at 19:01

Friday, Mar 13, 2015 at 19:01
Thanks Bill,

I only plan to run the fridge on 12v when driving and have the ability to charge the battery (fully) whilst driving. I will run it on gas when stopped if needed.
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Reply By: Member - Bill D - Friday, Mar 13, 2015 at 19:28

Friday, Mar 13, 2015 at 19:28
OK, I thought that I'd get reactions like that. I'd like to see the one the poor old moderator had to remove.

I'll now get my mate, who will remain anonymous, to look at this, especially the great photo from Bob Y.

In defence of my mate, he did say that he would always turn the gas off before going into a servo.

I might also mention that the 2 AGM batteries in my van are only charged from the solar panels on the roof. The towing Isuzu ute is not wired for van charging. The van fridge is a compressor type (ie not a 3-way - only draws 4 amps, as compared to 10 to 15 amps for the average 3-way fridge) and we've not run out of power yet. Perhaps we'll get into trouble if we get a run of cloudy days, but so far so good. Not much use to you, Ben, as you're already wired up, but this might prove to be a real and simpler alternative for others now that solar panels are so cheap.

Cheers

Bill
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Follow Up By: Bob Y. - Qld - Friday, Mar 13, 2015 at 20:26

Friday, Mar 13, 2015 at 20:26
Re the photo Bill.

Definitely not my photo, but probably a "borrow" from NT News. But a great example for your mate.

Bob

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