Installation of Battery in Jayco Poptop

Submitted: Tuesday, May 31, 2005 at 13:50
ThreadID: 23453 Views:24875 Replies:7 FollowUps:9
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Some technical assistance with fitting of a battery to a van please.

Wish to put a battery in my Jayco ( for internal lights only) and am trying to fully understand the following
1. Charging the battery, in van, whilst car is running
2. Linking the van battery to the caravan's transformer and using that battery for lights when 240v is not available
3. Topping up charge in van battery with a Ctek7000 charger

Present vehicle set up is an AGM battery in back of L/C which runs a car fridge, and this battery is in turn linked to a Redarc unit .
A 2nd plug is installed in rear of vehicle to use for 12v lighting etc.

I assume a link from the wiring to vehicle AGM Battery (and by default the Redarc unit), can be attached to caravan via an Anderson Plug.
From here I further assume that wiring to Anderson Plug , goes to the caravan's transformer and then is wired to the new van battery.
Have noticed some vans with a toggle switch in close proximity to van battery and ask is this to isolate 240 v from 12v power.

The transformer has a 240w wire plugged in permanently , and I wonder if I take this out to use the Battery Charger wil this create any problems.

Am getting it installed profesionally but am just trying to get it clear in my mind , beforehand, what are the steps and how it all fits together.


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Reply By: Member - Jeff M (WA) - Tuesday, May 31, 2005 at 14:31

Tuesday, May 31, 2005 at 14:31
Peter R, sounds like you answered all your own questions!! ;)
And with all that knoledge, why PAY someone to do it "profesionally" when (by the sounds of it) you could do it yourself with a minimal amount of effort. It would seem to me that all the hard work has been done, all you need to do is hook the two systems together... Via then anderson.
AnswerID: 113736

Follow Up By: Member - Peter R (QLD) - Tuesday, May 31, 2005 at 15:47

Tuesday, May 31, 2005 at 15:47
Jeff M,
I wish I shared your opinion re the knowledge factor.

The sequence outlined is what I assume happens , however is it correct , and what is the current role of the 240v wiring which is permanently switched on and connected to the transformer?
If, when new battery in van is installed, I am charging this battery and have terminated 240v wiring to transformer, and want to use 240v power in van at the same time, will this be possible?

A major lack of understanding with the proposed new setup revolves around the wiring process.
At present , I can run the lights off my vehicle when the caravan and car are attached, via the 12v hook up plug.
When the car is not connected to caravan the lights in van do not obviously work.

Because the 12v power from car to van at present runs indicator lights etc , I assume that a separate wiring needs to be done to the proposed new caravan battery.
In other words will I have 2 lots of wiring going into transformer, and two sets of plugs into car (present 7 point one and an anderson plug)?

If this is so does the new wire attach to battery and then back to transformer in the same place as the old wiring?
Does the toggle switch merely activate or deactivate the battery in van?

These will be basic questions to most but not to me, so would appreciate help in understanding the process.


FollowupID: 369813

Follow Up By: Member - Jeff M (WA) - Tuesday, May 31, 2005 at 16:38

Tuesday, May 31, 2005 at 16:38
Ok, firstly let me express the fact that I have no experience with cavaran wiring at all and have no idea how they work.

But. (everything before the but is bullsht).

But, it should be pretty basic to work it out. Just need to take it step by step.

1. Are the lights in the caravan 12v or 240v?
2. The 240v going into the van, does it run a 12v power supply and everything in the van is 12v or are there appliances in the van than use 240v?

Things that I see need changing:
Your probally better off to run some heavy duty type cable from the battery/redarc in the 4wd to the anderson plug. My understanding of using the andersan plugs is that they replace the standard plug all together. You would obivously then need to run some of the same wire to the battery in the caravan from the anderson plug for it to charge.

IF the caravan's accessories are all 12v then I would imagine that the 240v comming into the caravan powers some kind of 12v power supply. This is potentially the switch you are talking about, having the power supply hooked up while running off the battery could possibly cause some wierd things to happen, hence the switch to disable it while not pluged into 240v.

Now just so you know, I might be totally off the track with all this, it's all educated guesses from the info you've given me and my extremely limited understanding of caravan power!
FollowupID: 369824

Reply By: GOB & denny vic member - Tuesday, May 31, 2005 at 17:23

Tuesday, May 31, 2005 at 17:23
goodday peter
if your van is a late model jayco with the transformer under the seat you can ask jayco for a wiring diagram on how to connect the wires for the 12v from your battery but there unit (from memory) willalso act as a battery charger

AnswerID: 113761

Follow Up By: GB83 - Tuesday, May 31, 2005 at 18:40

Tuesday, May 31, 2005 at 18:40
The "thing" in a Jayco van is not a battery charger even though they (Jayco) say it is.

The out put voltage of this "thing" is just sufficient to stop the battery goung flat but will never never charge it more than about 50%. A battery charged to only 50% is not worth having!!!!! You will only hasten the death of the battery if this is the only charging you give it.

The only safe,good, reliable etc etc way is to bite the bullet and buy a 3 stage battery charger which will charge the battery right up to full. Depending on the siaze battery ( say 150 amphpour AGM) then a 20 amp 3 stage charger is the go.

FollowupID: 369846

Reply By: Ingenious - Tuesday, May 31, 2005 at 19:00

Tuesday, May 31, 2005 at 19:00
Member - Peter R (QLD)
Are you in Brisbane?
What year model Jayco is it? (There is a number of things to know about Jayco wiring)
AnswerID: 113773

Follow Up By: Member - Peter R (QLD) - Tuesday, May 31, 2005 at 19:38

Tuesday, May 31, 2005 at 19:38
I live at the Gold Coast (Hollywell) and it is a 2004 Jayco Freedom.

Can get to Brisbane in need .
Thanks Pedro
FollowupID: 369860

Reply By: Member - Peter R (QLD) - Tuesday, May 31, 2005 at 19:37

Tuesday, May 31, 2005 at 19:37
I am grateful for the replies to my queries and make the following comments.

You said in part

1. Are the lights in the caravan 12v or 240v?
2. The 240v going into the van, does it run a 12v power supply and everything in the van is 12v or are there appliances in the van than use 240v?

1. They are 12v
2. When connected to 240v we can run the fridge, boil a jug or run the microwave/air con and the lights as well. Not sure how it all works but without the 240v all we can run is the lights (when connected to car)
GOB and Denny,

I have the wiring diagram for the 2004 Jayco, but it means little to me. Perhaps it was the way I asked my question of Jayco (Melbourne) but I was unable to get an answer apart from plugging my Ctek7000 into the power point in lieu of the plug to transformer.


This is where my limited knowledge really shows up, and I appreciate your comments about the charging.
I have a Ctek7000 3 stage battery charger and will use that to recharge.

Thanks to all for your interest in answering my question.


AnswerID: 113782

Follow Up By: Peter McGuckian (Member) - Tuesday, May 31, 2005 at 20:40

Tuesday, May 31, 2005 at 20:40

I suggest that you drop onto the Yahoo Campertrailers group site and search the archive. You could also look for the book by Collyn Rivers on this very topic.

The site for the Yahoo group is link text

As far as I know the secret is to have a separate 12v supply to charge the battery which is turned on/off by a relay so that you are only charging from your aux battery when the car is running.


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FollowupID: 369872

Follow Up By: Member - Norm C (QLD) - Tuesday, May 31, 2005 at 20:42

Tuesday, May 31, 2005 at 20:42
Peter, I can't comment on a all of your issues, but:
AGMs are good batteries and charge faster than normal deep cycles.
You have a good charger. I have the same one. I charge my AGMs on 14.7V, which is what I was advised to do.
Since you have an AGM in the vehicle, my understanding is that it is OK to connect the van AGM in parrallel (via the Anderson plug). If one was not AGM, you should not connect in parrallel.
Even if you are charging regularly via the Anderson plug, do maintenance charging from 240V and the C-Tek when you can to ensure full charging.
Don't think you will ever be able to boil a jug, run a microwave or aircon without 240V, so no wiring change needed here. You should be able to run your fridge (if it is 12V) once you have the battery in the van. I think the Jayco's have an Electolux, which draw more power than most car fridges, but while ever you are connected to the car and running, it should be OK. Wouldn't leave it connected too long (more than a few hours)without the car running though. So you might need to rewire for the fridge. Most 240V / 12V fridges have an automatic power selector (ie you don't need a switch, they run off 240V if available; if not they auto select 12V). Don't have a clue about your fridge though.

Hope this helps.

Norm C
FollowupID: 369874

Follow Up By: Ingenious - Tuesday, May 31, 2005 at 21:12

Tuesday, May 31, 2005 at 21:12
Peter email me at for more info.

I do Jayco caravan power conversions all the time and they are quite different than other caravans, so there is specific things to go through to get a setup that you will be happy with.
FollowupID: 369882

Reply By: Member - Kingsley N (SA) - Tuesday, May 31, 2005 at 22:23

Tuesday, May 31, 2005 at 22:23

I reckon that Norm C has got the description of what happens just about right. My Coromal (brand new) has provision for a van battery. You need the extra battery for bush camps if you are disconnected from the vehicle. My truck has dual batteries and the auto electrician told me that if I chose to put a battery into the van it would be all OK because the wiring is in parallel. He ran a heavy duty wire from the auxilliary battery to the trailer socket specially for the fridge and van battery. He did not consider that it was necessary to change to an Anderson plug although we discussed it. I do not know the JAYCO set-up.

My van lighting is 12v and no switching is required when running off the vehicle or van battery compared with the 240v. There is a transformer in a cupboard that takes care of that. I am not sure of the specs on the transformer and how it would go acting as a battery charger. The car alternator provides sufficient current to keep both batteries topped up when towing. BUT if you stop for an extended break and leave the trailer connected, be aware that the fridge will suck all the energy out of both batteries in due course. If you have a 48 ampere hour battery the typical three way fridge set on DC for travel will suck out 10 -15 amps or more per hour giving about 3-4 hours life.

The electrician's advice was to disconnect the trailer plug if you will be stopped for a while. If you have a van battery also wired in parallel the total energy available is greater, but you would need to disconnect that also to avoid draining it, (hence the suggestion above regarding a switch to isolate the van battery). Batteries are great for running lights and compressor fridges (Waeco/Engel) but not for running three way fridges.

A problem occurred for me when we last camped on a powered site. I switched the fridge to AC but unbeknown to me the plug next to the fridge that goes into the 240v on board socket became dislodged. The fridge then switched to DC and ran OK for the overnight stop. The next night we were in a bush camp and when I went to use the van lights I discovered that the van battery was flat! Obviously the vehicle alternator could not bring it up to full charge. I had to put it on a 240V charger at the next stop for 24 hours to get it fully charged.

Tricky isn't it!

AnswerID: 113825

Reply By: AT4WD ADVENTURES - Tuesday, May 31, 2005 at 22:29

Tuesday, May 31, 2005 at 22:29

I am not familiar with Jayco but as a sparky would theorise as follows:


1. The van when plugged into a 240volt ac will supply all 240v outlets and 240v appliances within the van and by the sounds of it a 240v ac /12v ac transformer/rectifier for supplying power to the 12volt dc lighting.

2. The van when hooked to the car will only support the 12volt lighting direct from the vehicles 12volt supply and not via the Transformer/rectifier and zero 240volt ac outlets as no inverter is present.

3. I would imagine that there is a 240v/12v changeover relay in the ciruit somewhere to ensure safety when using either of the above inputs to the setup.


1. Place a 12volt battery into the van that will run the 12volt lighting when the car is not hooked up and not power any 240v ac equipment in this mode.

2. Charge this 12volt battery from the towing vehicle when mobile.

3. Charge this 12volt battery via a CTEK 240v ac /12v dc charger when 240volt input is available to be connected to the van.

If the above is a correct summary then let me know and I will try and steer you in the right direction from there.


Stuart M
AnswerID: 113828

Follow Up By: AT4WD ADVENTURES - Tuesday, May 31, 2005 at 22:34

Tuesday, May 31, 2005 at 22:34
In point one above of current setup I meant to type dc not ac after the it should be like this:-

240v ac /12v dc transformer/rectifier

and not like this:-

240v ac /12v ac transformer/rectifier

FollowupID: 369896

Reply By: AT4WD ADVENTURES - Tuesday, May 31, 2005 at 22:41

Tuesday, May 31, 2005 at 22:41
Also I would add that a 3way fridge should be connected to the vehicles batteries when mobile (engine running) and disconnected automatically via a relay when the engine is switched off.

This avoids any problems with batteries being drained by what is essentially a 10-15amp heating element. At no time do I see a need to have the 12volt power side of the fridge connected via the van battery as you will end up with a flat battery rather quickly.

To avoid the 240volt fridge plug coming adrift as described above it would best to use a captive syle of 240volt outlet to ensure this does not occur.

AnswerID: 113831

Follow Up By: Member - Peter R (QLD) - Wednesday, Jun 01, 2005 at 09:17

Wednesday, Jun 01, 2005 at 09:17
Stuart ,
Thanks for that , and all that you mentioned in your post is exactly what I want.
Would appreciate your further advices .

To Kingsley, Norm C and PeterMcG and others who have posted on this I am most grateful for the tips provided.

Have also sent an email to Ingeneous who works on Jayco so will shortly be full bottle (I hope) on this subject.

Thanks again

FollowupID: 369920

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