Dual Battery system

Submitted: Tuesday, Jun 14, 2005 at 19:41
ThreadID: 23864 Views:2251 Replies:6 FollowUps:3
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I'm a novice outback traveller and about to go on my first trip (for 3 months). My wife and I have bought a camper trailer and all the bits and are wanting to install a dual battery system for powering fridge etc. I've bought a '90 model Patrol to do the trip but plan to sell the vehicle when I return (I have a Jeep but I don't think its big enough for this trip). My question is - am I better off setting up the battery system to the trailer and then I can use it with the Jeep when we get back or is it better to set up in the vehicle (Nissan). I'd appreciate any advice?
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Reply By: Member - Chris L (QLD) - Tuesday, Jun 14, 2005 at 21:25

Tuesday, Jun 14, 2005 at 21:25
Darl I have a battery on my camper trailer I think it is a good way to go as in the fact that when you set up camp the fridge has power. and it gets charged by the nissan while you drive .I am running a 80l waeco and 2 12v fluro's off a 75amp deepcycle battery. haven't had any trouble with it cheers chris
AnswerID: 115783

Follow Up By: Mainey (WA) - Tuesday, Jun 14, 2005 at 23:36

Tuesday, Jun 14, 2005 at 23:36
A question; where is the fridge?

Another way of looking at it is;
setup the battery system up in the truck, and it is charged every time you start the engine.

If the battery system is in the camper and you go for a drive and leave the camper at the camp site you can't charge the battery!

Remember the fridge should be with the battery, or they will be disconected when in different vehicles (truck and camper) and you seperate the camper from the truck, which happens on a long trip!

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FollowupID: 371389

Reply By: old-plodder - Wednesday, Jun 15, 2005 at 08:07

Wednesday, Jun 15, 2005 at 08:07
I have been thinking about fridges and batteries in camping trailers too.

Fridge is in the back of the car at the moment, off the 2nd battery.

What is the advantage of having the fridge in the trailer? Just better access?
Do you need a heavier cable rated at about 30amps from car to the trailer to charge the battery?

Sorry about hijacking the thread, but these are possibly issues too.

What about more vibration and dust with the fridge being in the trailer?
Suppose it depends where you mount the fridge in the trailer!
AnswerID: 115825

Follow Up By: BenSpoon - Wednesday, Jun 15, 2005 at 12:29

Wednesday, Jun 15, 2005 at 12:29
I'd say 30A cable is the minimum.
Anything less and your fridge will turn itself off due to low voltage, and you will lose out on charging the battery in the CT. Check out cable used for outdoor low voltage lights. Generally cheap as, heavy gauge wire, flexible and has tough insulation.
Fridge in the trailer means you can park up the trailer securely and not lug the extra weight around when you do day trips.
Dust is a killer- search previous posts for solutions on ventilation of fridge boxes. Vibrations... much the same. Mount the fridge on a decent foam base and it should sort you out.
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FollowupID: 371445

Reply By: flappa - Wednesday, Jun 15, 2005 at 12:37

Wednesday, Jun 15, 2005 at 12:37
As Mainey has mentioned . . . where is your fridge ?

My fridge is in the trailer , and thus , thats where my battery is. Having said that though , I cant put a dual battery into my Patrol anyway.

You need a big battery on the trailer because , again as mentioned , its not getting charged as often. I currently have a 55amp hour deep cycle , that runs the fridge and lights etc , for about 2 days. I'm about to put a bigger 100 amp hour battery on the trailer , and expect to get 3 or 4 days out of it.

If you use decent wire , you get minimal voltage drop from the Vehicle to the trailer , and from the battery to the fridge. I have a dedicated circuit for my fridge.
AnswerID: 115864

Reply By: Darl - Wednesday, Jun 15, 2005 at 18:26

Wednesday, Jun 15, 2005 at 18:26
Thanks to everyone for advice, what a great site!
I've decided to install the dual battery system in the vehicle.
AnswerID: 115900

Follow Up By: Member - Jeff M (WA) - Wednesday, Jun 15, 2005 at 19:26

Wednesday, Jun 15, 2005 at 19:26
That's would be the best way to go IMHO, you could also put a couple of small 7amp/hr Gel Cells in the camper for lights, that way you wouldn't have to hook it up to the car each night.

PS Sell the jeep and keep the patrol LMAO!
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FollowupID: 371482

Reply By: Member - Chris L (QLD) - Wednesday, Jun 15, 2005 at 20:33

Wednesday, Jun 15, 2005 at 20:33
The fridge is in the trailer and it runs off a 75 amp deep cycle battery the 4wd charges it went driving our battery is good for adleast 3 days for the fridge and there is nothing wrong with plugging into the car for 1/2 hr to charge the battery cheers chris
AnswerID: 115929

Reply By: Member - Collyn R (WA) - Thursday, Jun 16, 2005 at 10:42

Thursday, Jun 16, 2005 at 10:42
The ongoing mention of '30-amp' etc cable puts shivers down my spine!

This so-called rating is simply and only an indication of how much current that cable can carry before the insulation melts. It varies hugely from maker to maker and cable type to cable type as there are various heat-rated grades of insulation.

In other words the rating gives no indication whatever of voltage drop.

The most effective way to determine this is as follows (understanding that we are talking of conductor length not cable length: ie if twin core cable then a three-metre run is six metres of conductor).

Length of conductor (in metres) times maximum current (in amps) times 0.017.

Dividing that by the desired max voltage drop (ideally 0.2) gives the size conductor required in square millimetres. Round up to the nearest available size.

Then note that auto cable is rated by overall diameter. 6.0 mm auto cable is about 4.6 sq mm, 4.0 mm is only 1.8 sq mm. 2.0 mm is less than 0.5 mm.

Most people buy cable that's about 50% too small and that why many 12-volt fridges perform badly.
Collyn Rivers
AnswerID: 116009

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