Trailer and car wiring

Submitted: Monday, Sep 15, 2014 at 18:11
ThreadID: 109511 Views:2916 Replies:3 FollowUps:4
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I have finally finished the new wiring in my trailer to incorporate a CTEK250S to supervise the charging of the batteries. I now have one in the car and the trailer. Here is a wiring diagram

Can some of you 12V gurus cast an eye over it to see if I have got it right? I would appreciate any constructive criticism or suggestions. One thing that I pondered over is whether to get the D250S in the trailer to listen to the auxiliary battery in the car or the car starting battery. I opted for the auxiliary battery because I figured that if there was some fault it would be less likely to flatten the starter.
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Reply By: olcoolone - Monday, Sep 15, 2014 at 19:08

Monday, Sep 15, 2014 at 19:08
The feed for the trailer should be coming of the starter battery and not the vehicle mounted auxiliary.

How you have wired it you have a maximum current of 20 amps going into you vehicle auxiliary battery through the vehicle mounted Ctek and then 20 amps getting pulled out of it by the second Ctek in to the camper auxiliary battery.

Your vehicle mounted auxiliary battery will not get charged correctly until your camper auxiliary battery is nearly full.
AnswerID: 539135

Follow Up By: olcoolone - Monday, Sep 15, 2014 at 19:12

Monday, Sep 15, 2014 at 19:12
BTW what is charging the vehicle auxiliary battery, if it is only the solar it will not keep up.

FollowupID: 823733

Follow Up By: Yabbo - Monday, Sep 15, 2014 at 19:19

Monday, Sep 15, 2014 at 19:19
Well spotted! I have neglected to put the connection from the positive side of the car battery to the car aux. I thought there might be some issue like this with it hooked up to the car aux. Thanks.
FollowupID: 823736

Follow Up By: Yabbo - Monday, Sep 15, 2014 at 19:20

Monday, Sep 15, 2014 at 19:20
I mean to the input of the Ctek!
FollowupID: 823737

Reply By: Member - John and Val - Monday, Sep 15, 2014 at 20:18

Monday, Sep 15, 2014 at 20:18
Hi Andrew,

Suggest have a look at Allan B's recommendations here.

Allan's final diagram probably does basically what you want - with the dc-dc charger caring for the trailer battery, and the vehicle aux battery charged directly by the alternator.

You'd need to feed the solar regulator to the trailer battery, add a few meters so you know what's happening and the job is done. If you have meters, I wouldn't bother with the low voltage cutout - you'll know before things stop working! Suggest if you've got moveable solar panels that you use anderson plugs to connect their controller to the trailer battery. That way you could alternatively easily plug them into the vehicle aux battery using the trailer-to-vehicle anderson connection.


J and V
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AnswerID: 539138

Follow Up By: Yabbo - Monday, Sep 15, 2014 at 22:03

Monday, Sep 15, 2014 at 22:03
Thanks John, they are very useful diagrams. The solar regulator in the trailer is a Redarc and it has a monitor that gives me lots of data. SOC of the two batteries, the current from the panel, the no of Ah into each etc. The low voltage cut out is a bit belt and braces but I figure it will save a battery if I'm away from the trailer on a cloudy day.

I will change the connection to the trailer Ctek so it is connected to the starter battery as suggested.
FollowupID: 823755

Reply By: Green Rv - Tuesday, Sep 16, 2014 at 08:25

Tuesday, Sep 16, 2014 at 08:25
G,day Yabbo
on the trailer side of things you have a solar reg befor the ctek. not needed as the ctek has it built in

and a low battery disconnect also i thought that was built in to ctek.

how would it go if in the cars system you added a smartpass to the d250s and passing 80amps to the van via anderson plug then you could keep the solar reg on trailer which should also have a low voltage cut out and built in volt amps ect meter for both power in and out

i would also cut out the battery switch in trailer and hook up in series
as long as the batteries are both in good condition you should have no problems

a good read solar that really works by collyn rivers from EO store

just my thoughts

AnswerID: 539155

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