A somewhat contentious subject I suspect but I have been told by

my car electrician that the combined draw of batteries charging in

the am after draining overnight and especially the frige puts enormous

strain on the alternator. In my case the alternator replacement is

a horrendously expensive matter and since I read that there's no

reason why the gas cannot be run sans tunnels and refuelling,

then why not?

Is unplugging the Anderson plug all that is required?

Batteries will charge with the solar while I drive, hopefully all else

will function as normal.

What's the thoughts of others?

Brodie

Brodie Allen hi

We have very seldom run our 3 way while on the move living in Queensland, mostly only travel about 2 hours, then while stopped run the refrigerator on gas for the half an hour while we have our break and do the same at lunch time which would be a little longer.

In ten years we have been travelling with our caravan our 3 way we could only count a hand full of times we have switch onto 12 volt between March and October and never seen any loss of real temperature in that time, very pleased with our 184 litre, 2 door, 3 way refrigerator. 

Ps. I have our frig wired to the caravan batteries, about 2 metres of heavy cable supported by 340 watts of solar and 2 x 110 amp deep cycle batteries, also can be charged via the car though an anderson plug.

I never travel with fridge on gas whilst driving, My (automatic) Dometic fridge is programmed to switch to 12volt when gas is turned off at valve.

It is unwise to travel with un-isolated gas - there would be a potential for vibrations from road creating a leakage somewhere. In the unfortunate event of a road accident the probability of leakage/explosion would increase exponentially.

I am uncertain of gas regulations in each State but I am of the belief it is covered in the transportation of dangerous goods regulations and "Each cylinder valve must be closed during transit, and any equipment that is connected to them must be unattached. Furthermore, all gas cylinders must be secured properly and should not project beyond the sides or end of the vehicle".

Gas fridges use a lot when running off 12v, about 12 to 15 amps. To get the most while running off the alternator. You need DC-DC close to the battery & fridge to make up for voltage loss. Otherwise the fridge won't cool as quickly.

I use a DC-DC charger for my compressor fridge, & we are only in a car. Probably only a third of the run for wiring compared to towing a caravan.

Also keeping the fridge full with plenty of thermal mass helps stabilize fridge temperature.

Hi Brodie unless you specify the components that you have it is hard to give you an answer and solution. 

Firstly, I have Dometic RU808X 3 way fridge.  I can run that on gas as Im driving but when I pull into a service station and turn the ignition off the gas is extinguished.  Turn th ignition on again to drive out and the gas reignites 10 minutes later.

Why run a fridge on gas though when solar is free.  I have no idea whether your alternator died or it was just a comment by your auto electrician but there are thousands of people charging their batteries for their alternators.  When you say that you cant get 12V at the fridge are you saying you have tested with a multimeter and are getting below 12V or are you saying that you get no power at all?

Brodie, I suspect your fridge is wired incorrectly and it is Earthed through to car not the caravan.

I have an old fashioned set up, which is good in some ways as my replacement alternator is pretty cheap, even to the extent that I was considering carrying a spare as the 27 year 290,000Km original one must be due to fail! LOL

I have changed my 12v feed from the car to the van so that it terminates on an Anderson plug that I can manually connect to either the van battery or to the fridge (also both terminating on Anderson Plugs).  I should look into a switch I suppose. 

A simple relay connected off the Truck's accessory wiring switches the 12v feed to the van on or off with the ignition switch.  You can doo that sort of thing with old technology & few controller computers!

When traveling for reasonable times I connect the 12v feed straight to the fridge & it works beautifully, only loosing a couple of degrees at worst.  Mine is the original fridge that has no auto change over or anything else auto.  Sometimes a good thing I think.

The van roof solar keeps the van batteries topped up.

Of course I help the whole process in hot weather by keeping a few frozen water containers in the fridge & the freezer usually full. As we rarely camp without 240v power, recharging the van batteries is rarely an issue.

Oh, BTW, I help retain coolness in the fridge when in daily use, by keeping all its contents in sealed plastic containers.  Very little cold air spills out when we open the fridge door.   But I digress  (again).

Years ago when traveling in the tropics in summer, I would often drive with the fridge running on gas, but never felt comfortable with the practice.  Don't need to take that risk these days.

I could only ask why would anyone take the risk.

https://www.xtendoutdoors.com.au/blogs/general/safe-tow-caravan-fridge-gas

plenty of info on the net why travelling with the fridge on gas is dangerous.

The first van I ever bought had evidence of a fire from the gas fridge as noticed when I had a tech doing other work (damaged wiring)

Maybe have a sign on front back and sides of the van to warn others that you are prepared to do something as dangerous as you are suggesting. 

Brodie Allen wrote:

---

Thanks Tim Tim,

Theres power because the internal light comes on, but no matter how I try
the frige will only go to 12v when the motor is running and anderson plug
connected.

I have 4 arrays on the roof, 200ah of solar but that's academic - I only
want the frige to run off 12v when travelling and Anderson disconnected.

Won't acknowledge batteries or solar ever.

Not a great drama but I keep hearing of others running off solar rather
than batteries or alternator and wonder why I cannot.

Setting off am tomorrow for 4-or so months into the wilderness and thoughts
running thru my mind in torrents.

BRODIE

See yer soon Mother - hang a flag out!!

---

Hi Brodie,

The reason your fridge light comes on but you can't get it to cool on 12v without the tug running is your fridge has two 12v DC inputs. One direct from van battery and runs only the control electronics, gas ignition, and internal light. The other is the high power 12v input for the heating element, and that traditionally is wired straight to the car alternator and doesn't go anywhere near your van battery, to avoid running it down.

However, if you want to use your van's solar and battery system while underway there's nothing stopping you re-wiring the fridge high power 12v input to the van battery, but you have to have a backup plan for those occasions where the solar isn't sufficient to both charge the batteries and run the fridge - 15A continuous draw can flatten even quite a large battery bank if there's no sun!

There's many options how to do this starting with a simply manually plugging/unplugging between alternator feed and van battery, through to a couple of relays to do it semi-automatically, to the ideal solution of a dual input DC/DC charger with solar priority which will juggle the alternator, solar, batteries, and fridge for you without you having to do a thing.

I chose to go the with the DC/DC charger and it worked very well, although I couldn't really justify the cost involved in terms of fuel savings as I'm not a full time nomad, but I did get a bit of a greeny glow by using the solar system to it's max potential!

Suggest you have a chat to your auto sparky mate and get him to explain the options and how much it'd cost versus the benefits for each.

Hi Brodie,

If I read this right, when the Anderson 12v is connected from car to van and you run the engine then the fridge will switch over to 12v operation. The fridge will then draw around 15ah from the alternator. Not a big deal for any alternator.

Now , I assume the 12v Anderson is also connected, through a dc>dc charger to the house batteries in tandem with the solar controller. However, you don't want any of that and want the fridge to run off 12v directly from the batteries with the solar controller supplying power to the fridge at the same time charging the batteries.

How about running the fridge on 240v through an inverter while you are travelling. The solar controller will feed the batteries while the batteries are feeding the 240v inverter and may provide some or all charge to the batteries at the same time. Depending on the solar input/weather you may find this to be a win overall.

Thanks MAMIL.

Which raises my question:

What happens if connected to solar, when the full amperage (whatever that is)

is not fully available from solar.

Do we just get a reduced efficiency or does it die altogether?

Brodie

Brodie Allen wrote:

---

Thanks MAMIL.

 

Which raises my question:

What happens if connected to solar, when the full amperage (whatever that is)

is not fully available from solar.

 

Do we just get a reduced efficiency or does it die altogether?

 

Brodie

 

 

---

Hi Brodie,

The fridge is running off the van battery, which in turn is charged by the available charging sources - solar (through a solar charger), and/or the Anderson feed from your tug's alternator (though a DC/DC charger). The battery is the buffer if you like, and it's the battery voltage the fridge is getting, not solar voltage, so as long as the battery has a healthy voltage - basically 12v or above - the fridge will continue to cool well. However, if the total inputs to the battery (solar and/or alternator) are less than the total outputs (fridge and any other loads running) then the battery will start to run down and once the battery voltage drops below 12v then yes, the cooling action will become less effective because it's just a fixed resistance heating element - think element in a kettle - so as voltage drops, cooling effectiveness drops proportionately. Luckily, as you have lithium batteries they have a very flat discharge curve, so will maintain a healthy voltage to run the fridge until your battery is nearly flat, but you really ought to be switching the fridge over to AC or gas long before the battery is completely flat anyway!  

Perhaps if I describe my system that will help to clarify how it works. I have a Redarc Manager30 in the caravan which is basically a dual input DC/DC charger combined with a mains charger. The DC fridge input is connected as a load to the van battery, through a relay (more about that later). The fixed solar on the roof of the van is connected into the Manager's solar input, and the Anderson feed from the tug is connected into the Manager's car input. When solar is available the Manager will use it to keep the battery charged. If the available solar is less than the fridge output, the Manager will automatically top up the charge with some input from the tug's alternator. When there's no solar at all the Manager will take all the charge from the tug's alternator. When there's no solar AND the tug isn't attached (or engine turned off) then the battery starts to discharge and that's the time to switch the fridge over to AC power or gas. However, if I forget and the fridge continues to run the battery down, the Manager has user adjustable functions which I have set to sound an alarm when the battery gets down to 25% state of charge, and then automatically disconnect the fridge (via the relay I mentioned earlier) if it continues down to 20% state of charge.

There are of course, other ways of doing it, with other products, and the the Manager 30 is not a cheap system, but I have installed three of them over the years in my caravan, camper trailer, and a stand-alone battery box, and it manages the situation like you and I have very well, and is a quality bit of kit, so I have no hesitation in recommending it!

Attached is Redarc's wiring diagram of how the Manager 30 fits in. The fridge is the "Non-essential loads" in this scenario.

Hope that all is of some help for your situation.

ONE word...... NO.

A bumpy rad you could go "boom"_ As said. buy some panels

I ran 4, a mix of 85 to 110w panels on van plus 2 more 110w on roof of Patrol with Anderson plug to van. for 17yrs plus. DC fridge. never a problem with 2 x 110A batt's in van and 2 more in Patrol for fridge'freezer. (80 ltr Waeco). Whish is for sale if anybody interested.

Plus a 3.8kva Genny for Air Cond.

Hi Brodie,

There seems to be an over-complication of thought here in seeking a solution that is not even required.

All because an auto-elec made a comment contrary to the normal way of van connection and operation.

Your system works the way it should and has been designed to work that way. Your fridge will automatically select 12V operation when connected to the tow vehicle when you start the engine.

The 12V feed will also charge the house batteries connected through a dc>dc charger. The solar charger will also feed the house batteries.

Any alternator will easily supply the required amps for such a connected system. Perhaps an old vehicle with a generator system may struggle!

Your system is by far the normal connection system to charge house batteries and run an AES fridge.

I would seek more information regarding why your tow car alternator would struggle charging the van house batteries and to run the AES fridge at any time of day.