wiring diagram

Submitted: Saturday, Mar 22, 2003 at 15:40
ThreadID: 3993 Views:18384 Replies:9 FollowUps:10
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we have recently purchased a caravan. What we would like to do is carry an extra battery which can be charged whilst driving as well as the one in my vehicle- a holden rodeo. We want to mount the battery some where on the caravan.Could one of our members supply a wiring diagram or any hints which may be helpful to us.
Mark and Estelle
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Reply By: Will - Saturday, Mar 22, 2003 at 16:01

Saturday, Mar 22, 2003 at 16:01
nu2oz I cant help with the wiring diagram, but make sure the battery is externaly vented, idealy in a separate compartment because the gas put off by the natural process of a battery is poisonous and explosive.
And as one that has had a battery explode in front of me it is a very scary thing. (acid in eyes and a thundering explosion, deaf for 5 minutes)
AnswerID: 15857

Follow Up By: nu2oz - Saturday, Mar 22, 2003 at 17:02

Saturday, Mar 22, 2003 at 17:02
thanks for your reply, its always good to get safty hints , i will make sure to fit the battery out side the caravan.
FollowupID: 9668

Follow Up By: Scott - Sunday, Mar 23, 2003 at 04:50

Sunday, Mar 23, 2003 at 04:50
No need at all to fit the battery outside the caravan. There are thousands of batteries fitted internally in caravans and buses without any issues. Just buy a clip on lid plastic storage box the battery will fit and stick a pipe in it to vent to the outside of the van and seal the wires going into the box. Other solution is to have a small pipe that will actually scoop air into the enclosure and another hole to let it out. Hydrogen gas is only a real problem if you are over charging the battery and causing the battery to extensively gas. Just do a search on the net about sensible battery installation and basic precautions. Do a search here in the archives for battery installation in your van as there was some excellent stuff written in the past that put me and others on the right track. I rewired and refitted our tour buses with information given here using Redarc battery isolators and our second batteries are now getting properly charged and have another thing fixed I do not have to worry about giving trouble and know it works.
FollowupID: 9707

Reply By: Bob Y. - Saturday, Mar 22, 2003 at 16:46

Saturday, Mar 22, 2003 at 16:46
nu2oz, Suggest you first go to a marine shop/chandlery, and purchase an enclosed battery box, for the 'van.

Think you would also need following:
8mm twin cable, from vehicle battery to 'van battery, together with convoluted tubing, for protection,
H/Duty on-off switch adjacent vehicle battery,
Circuit breaker, ditto,
Anderson plugs, rear of vehicle, and 'van A-frame,
Various cable fittings etc Zippy ties - big mobs...

Whitworths are one good marine shop. www.whitworths.com.au
Also auto electricians.

Am sure others may respond in more detailed manner. Also do a search of archives, this has come up before. Hooroo...
AnswerID: 15861

Follow Up By: nu2oz - Saturday, Mar 22, 2003 at 17:04

Saturday, Mar 22, 2003 at 17:04
thanks for the list of items, i shall start pricing up the job ,i feel this is going to cost more than i thought,
FollowupID: 9669

Reply By: GaryInOz - Saturday, Mar 22, 2003 at 17:20

Saturday, Mar 22, 2003 at 17:20
Mark and Estelle,

Relatively straightforward. You will need the heaviest cable you can find going from the "B+" terminal on tha alternator via an isolator to the rear of the vehicle and terminating in an "Anderson" type connector (high current capacity), with the earth from an immediately adjacent point on the chassis, once again with heavy cable. Don't try to use the usual trailer plug, it can't take the current. The caravan side should also be done with heavy cable up to the battery. There are battery boxes available from Supa Cheap Auto (I believe, post 3963, reply 9) for about $99 with some cable, a circuit breaker, and battery test function (light/meter?). Thanks to the boom (no pun intended) in high power audio, heavy cable is relativly easy to obtain, get the biggest guage you can (lowest number), 4 Ga at the minimum. The reason for the heavier cable than you would think necessary is to reduce the resistive losses which would not allow your caravan battery to be fully charged over that distance from your alternator. Take the power for the battery isolator from the "B+" terminal of the alternator, DO NOT take the power from the + terminal of the car battery as the short strap from the battery to the alternator usually has a bit of resistance to lower the peak charge to the battery (stops excessive gassing). Put a large fuse in the cable just after the isolator and run a monitoring light to the interior of the car (after the fuse) to indicate the condition of the fuse. Due to the heavy currents in the car to caravan cable make sure the cable is SECURELY tied down with non-metalic cable ties every 4-6" or so to reduce vibration/chafing, an extra measure of safety would be to route the cable through 1/2" PVC electricians conduit with intermittent notches to allow the cable to be secured in the conduit (stops it rattling!) This is to prevent the soft insulation on the cable chafing through and touching the metal chassis of the vehicle. As for batteries I would use two small "Odyssey" Lead-Tin batteries paralleled together (second one could be used as a car battery if you car battery dies in the outback). I have done a bit of research into these batteries and believe them to be excellent for both starting and deep cycle uses, with the added bonus that they will accept a high rate of charge (can be FULLY charged in about one hour from dead flat) without detrement to their ongoing performance. I would use 2 x 28 Ah giving you about 36-48 hours use between charges, even then a one hour blast with the car (or portable generator depending on its output) should have the batteries up to charge. Not cheap but very,very good!

Sorry the explanation was a bit long, but I hope this helps. Have a good trip.
AnswerID: 15863

Follow Up By: GaryInOz - Saturday, Mar 22, 2003 at 17:25

Saturday, Mar 22, 2003 at 17:25
Odyssey batteries do not need venting, (absobed gas mechanism)


FollowupID: 9671

Follow Up By: joc45 - Saturday, Mar 22, 2003 at 18:20

Saturday, Mar 22, 2003 at 18:20
Suggest a voltmeter to monitor the battery.
Jaycar sell quite a good digital one, which includes an indoor/outdoor thermometer for $39.95, code XC-0116.
The outdoor part of the thermometer is on a long lead, and can be used to monitor the fridge temp. Can be easily mounted with some double-sided tape.


FollowupID: 9673

Reply By: ThePublican - Saturday, Mar 22, 2003 at 18:04

Saturday, Mar 22, 2003 at 18:04
Nu2oz,, look at rotronics ,simple easy ,not overly expensive [depends on type of 2nd battery you wish to use] ...try www.rotronics.com.au
AnswerID: 15869

Reply By: nu2oz - Saturday, Mar 22, 2003 at 18:05

Saturday, Mar 22, 2003 at 18:05
thanks gary
the information is great and will be very helpful i found your discription easy to follow .
thanks again
AnswerID: 15870

Reply By: Graeme Degotardi - Saturday, Mar 22, 2003 at 19:55

Saturday, Mar 22, 2003 at 19:55
Mark & Estelle,

I have just gone thru the exercise as we too just purchased a van with two batteries. We found after a full day's driving the batteries were not being charged. I have a 100 series L/C with a starting battery and two auxilary batteries, and had a Pirana duel system. After a lot of research we finally found we had to fit a Rotronics 3 way system. This charges and monitors first the starting battery, then the auxilary batteries, then the van batteries. When it switches to the van, we get 13.9 volts to the rear of the car charging only the van. Rotronics is not cheap and if you do not have a second battery in the car, I would suggest installing the duel system.
You will need a 110 - 130 amp/hr battery in the van and fitting a duel system you can enjoy ample lights and run a fridge to keep the beer cold.

Hopes this helps and adds to the confusion !!

AnswerID: 15878

Follow Up By: Scott - Sunday, Mar 23, 2003 at 04:21

Sunday, Mar 23, 2003 at 04:21
The batteries were only not being charged because the set-up was not wired correctly or probably with the appropriate equipment. You did not have to fit a Rotronics system at all. Rotronics are substantially over priced. There is also no reason to fit such a large battery unless it is required.
FollowupID: 9706

Follow Up By: rodeoowner - Sunday, Mar 23, 2003 at 10:51

Sunday, Mar 23, 2003 at 10:51
Graeme, like Mark & Estelle replied. Contact Rotronics. They have a system designed to meet your exact needs.
FollowupID: 9712

Reply By: Eric - Saturday, Mar 22, 2003 at 23:12

Saturday, Mar 22, 2003 at 23:12
There is some good information posted already but there is a dangerous error, about wire size, the maximum current you can safely charge at is about 10 amps this is easily carried by 3mm wire and you normal caravan plug. The dangerous part is if you use very heavy wire and plugs when you are starting the motor the auxilary battery can be overloaded because it does not have the protection of the resistance in the charging wire. the danger is you can burn out the wire between the alternator and the starting battery, don't get confused about charging current if you have 14.2 -14.8volts at the alternator the current will look after itself. Eric.
AnswerID: 15892

Follow Up By: GaryInOz - Sunday, Mar 23, 2003 at 00:46

Sunday, Mar 23, 2003 at 00:46
The Odyssey battery is quite a bit more tolerant of a high charge current and in fact should be charged at about the Ah rate of the battery, but it is typical of most lead acid batteries to be able to withstand a reasonable rate of charge for a period of time. The actual reason I specified the heaviest cable/connectors you could find was for the reduced voltage drop across it (yes, even charging at 10 amp) can be anything up to .25-.5 volt, plus the slight loss across the isolator itself which would not allow the caravan battery to come up to full charge, a definite battery killer, especially deep cycle lead acid.

As the vehicle is being started the alternator is not putting much charge into the battery which leaves the circuit as :

caravan battery>plug and socket> car cable>fuse>isolator>alternator post>alternator to start battery strap>start battery>starter cable>starter.

This is if the isolator does not disconnect the caravan battery during starup. If it does then it would not get past the isolator.

If the isolator did not disconnect the caravan battery during startup of the vehicle then you would be trying to pass starter current through 3mm cable and a trailer connector up to the starter battery, wouldn't you? Typical voltage of a battery when starting is 8-10.5 volts leaving about 3 volts dropped across a dead short (difference between the caravan battery voltage and the start battery voltage under load via the 5 metre caravan cable run). I would say the 4 Ga cable, Anderson plug, and alternator to start battery strap would withstand it a lot better than 3mm cable and trailer plug. Sounds like a recipe for fried wires and molten trailer plug to me.
FollowupID: 9703

Follow Up By: Scott - Sunday, Mar 23, 2003 at 04:17

Sunday, Mar 23, 2003 at 04:17
Eric unfortunatly your information is totally flawed.

GaryinOz your information is a little more tolerable, but 4gauge which is 25mm2 is over the top, but there are also other basic errors.
FollowupID: 9705

Follow Up By: GaryInOz - Sunday, Mar 23, 2003 at 09:24

Sunday, Mar 23, 2003 at 09:24
Scott, as someone that has had a lifelong interest in electronics and a radio trades background, with a ticket that says that I am qualified to sit on Mt Dandenong and run the TV/Radio transmitters, (and yes, I did try to simplify my answer, perhaps a little too much) I would be interested to hear where these "basic erreors" are.
FollowupID: 9709

Reply By: Graeme Degotardi - Sunday, Mar 23, 2003 at 12:01

Sunday, Mar 23, 2003 at 12:01
Scott, appreciate your comments, but your info is incorrect. The system I had was done by a Piranha authorised dealer, and as I run a 60L Engel fridge, I needed the two auxilaries in the car, and if we had to stay for a few days, we would also have to use our solar panels. We have a 22ft van with three solar panels and 3 x 130ah batteries and they run a 190l 2 door 12v fridge plus lights, tv etc. Our electrician explained that with the system we had we were only getting an overflow and we would never be able to charge 2 batteries in the car plus 3 in the van. Since we fitted the 3 way Rotronics unit we have had no further problems.

As a matter of interest, most larger vans now install an Anderson plug to take the larger wiring needed and we recently bought a Kimberley Kamper which also has the Anderson plug. We were also told by Kimberley that we would have to isolate the charging system if we wanted to fully charge the 130Ah battery.

I agree that the Rotronics is not cheap, but long term it will pay for itself.

Mark, if you ring Trevor at Walkers Electrical at Brookvale in Sydney he will help with advice as he fitted the Rotronics for me -and I don't get a commission. Hope all this helps.

AnswerID: 15903

Reply By: alex - Sunday, Mar 23, 2003 at 21:02

Sunday, Mar 23, 2003 at 21:02
I have just purchased a Jayco Finch outback and am going to fit a battery to the A frame in a box. On the box I am going to wire up a female trailer plug and only wire up the hot wire pin so I can run my lights in the van, un plug it from the car plug it to the battery. To charge my battery I'm going to use a solar panel mounted on the caravan when travelling or pull it off and put in the sun while camping. I only need the battery for lights and a shower. hope this helps, something different.

AnswerID: 15938

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