Trailer electrical system

Submitted: Wednesday, May 15, 2013 at 18:11
ThreadID: 102225 Views:3705 Replies:3 FollowUps:12
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I know similar questions have been asked before, but there seem to be many possible answers depending on the base parameters. So here goes with my parameters.

I have a Supamatic Drover on order from Cub and I will be towing it with an Amarok. Cub are installing two 100 amp/hr AGM batteries. I want to charge those batteries via an Anderson plug connection from the Amarok's alternator and also via solar panels. Various people sell kits with battery isolators of varying intelligence to do the alternator charging and there are many MPPT controllers available for charging from the solar panels. However, the Redarc BCDC 1225 DC/DC charger has come down to a reasonable price and looks to me to offer a better integrated solution.

Am I right in thinking that an isolator would not be required as the BCDC 1225 effectively performs this function as well? Are solar panels readily available for RVs without in built controllers and able to deliver unregulated power to the BCDC 1225 as it requires. Could I use my CTEK mains charger at powered camp sites without problems with the BCDC 1225?

Cheers, Peter H
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Reply By: Ross M - Wednesday, May 15, 2013 at 18:53

Wednesday, May 15, 2013 at 18:53
G'day Peter.
The Redarc unit should do the job, the two 100 ah, if discharged about 1/2 will be the same as one battery capacity and the charger will take a fair time to fully charge them again, all depends on how much charge AH have to be replaced. A 100 ah requirement with 25 amp input, in theory 4 hours, but will be much longer.
The redarc is best close to the batteries in the camper and is also cooler than an engine bay which is HOT. Just supplied by heavy leads and anderson plugs the BCDC should perform well.

I suspect Amarok may have an alternator which is ECU controlled, not sure about this, if it has there will be a certain place for the BCDC negative lead to be connected so the ECU senses the amp flow and demand on the battery.
Best to check on this to see if it is required and where to connect. On Rangers it is at the chassis/body end of the negative battery lead because the amp sensor is up near the battery neg terminal.
In these cases the BCDC neg lead doesn't go on the battery negative post clamp.

There are many solar panels available, with and without generic regulators fitted on the panels. Depending on the price and size you need, it isn't hard to bypass the regulator if fitted so there is full panel voltage available to be fed to the BCDC unit. If none = no worries.

A mains powered Ctek should be quite ok to plug directly to the batteries when in a 240v camp. The BCDC unit will just see there is a battery there and adjust or hold back as is necessary if panels are active.

Ross M
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Follow Up By: KenInPerth - Wednesday, May 15, 2013 at 19:51

Wednesday, May 15, 2013 at 19:51
Peter

I think Ross would also agree you do not need a battery isolator as per your query as the Redarc will take care of that for the alternator input.

Just another note, but completely different circumstances, I use a Ctek 250S Dual and when if leave that connected to the batteries and hook up a smart charger directly to the batteries the Smart Charger I used (not a Ctek) gets very confused (I think when it is trying to determine a few things prior to actually charging).

But the Redarc and Ctek Charger combination you are looking at are completely different units and so may not be a problem, but you will possibly only find that out when you try it.

Ken
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Follow Up By: Pelikan - Thursday, May 16, 2013 at 12:07

Thursday, May 16, 2013 at 12:07
Thanks Ross,

That's very helpful. What does ECU controlled mean and who would be able to tell me if this applies to the Amarok? The VW dealers know nothing about the electrics.

Peter
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Follow Up By: Nomadic Navara - Friday, May 17, 2013 at 00:35

Friday, May 17, 2013 at 00:35
Peter, the newer vehicles do not have regulators in their alternators. The ECU (computer) that runs the motor also controls the alternator output. This is done to help the vehicles conform to the modern emission standards. The charging voltages are lower than they used to be after the motor warms up.

There are two models of the Redarc boosters. Both have battery isolation in them. The older ones may not work successfully with the newer alternators as the input voltage is used is used to trigger the isolation. Between the lower alternator voltage and the voltage losses inthe supply cable you may not be able to achieve a high enough input voltage to work properly at full output. The newer ones with a LV model number subscript use a separate wire to the tugs ignition circuitry to sense when the motor is running and switch the isolator..
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Follow Up By: Pelikan - Friday, May 17, 2013 at 08:59

Friday, May 17, 2013 at 08:59
Thanks PeterD,

Please see my reply to John below. A Redarc dealer has told me I need the LV model, but a Redarc technical advice man yesterday told me I don't need it for the Amarok.

Peter H
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Reply By: Nomadic Navara - Wednesday, May 15, 2013 at 19:48

Wednesday, May 15, 2013 at 19:48
Portable panels come with regulators. If you look at the others they probably will not have regulators.
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Reply By: olcoolone - Wednesday, May 15, 2013 at 21:04

Wednesday, May 15, 2013 at 21:04
The BCDC 1225 may be a little on the small side for two 100ah batteries, the 1225 will do it but you might be better looking at the 1240.

The BCDC is an isolator and yes you can get solar panels without in built regs, have a look at "Bit Deals", their panels are OK quality and they do many sizes.

If connecting up a 240v charger you will have to connect it after the BCDC...... Car charging system - BCDC - Battery charger - camper batteries.
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Follow Up By: Pelikan - Thursday, May 16, 2013 at 12:10

Thursday, May 16, 2013 at 12:10
Thanks olcoolone, I will have a look at the 1240.

Peter
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Follow Up By: Member - John and Val - Thursday, May 16, 2013 at 18:11

Thursday, May 16, 2013 at 18:11
Pelikan,

While I agree the BCDC1240 might be the way to go, it is capable of pumping 40 amps into the batteries and may draw 45-50 amps from the alternator to achieve this. That's a lot of current. Suggest check that your alternator can supply, and that it can supply for lengthy periods. You may be better off sticking with the 1225 which is unlikely to draw more than 30 amps from the alternator.

The other consideration is that the amount of charging you require depends on your energy usage, and is not directly related to your storage capacity.

Cheers

John
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Follow Up By: Pelikan - Thursday, May 16, 2013 at 18:22

Thursday, May 16, 2013 at 18:22
Thanks John,

I was hoping I would hear from you. Am I on the right track otherwise?

Chers, Peter
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Follow Up By: Member - John and Val - Thursday, May 16, 2013 at 19:20

Thursday, May 16, 2013 at 19:20
Pelikan,

Different users have different requirements. You travel plans are an important variable - like how long are you going to be stationary and living on solar. How much can you rely on the vehicle to provide the charging? Are you running more than 1 fridge, or using it as a freezer - more critical variables.

"Am I on the right track otherwise?" I can't judge your requirements and don't know your likely movement patterns, so really can't comment except in a very general way. Our rig has 2x100Ah batteries, 150W of solar and a 30A dc-dc charger. I was surprised to find that the dc-dc charger provided most of the charging. Why surprised? I underestimated how much and how often we are travelling.

I reckon 200 Ah is good, a dc-dc charger is extra good, and solar a nice touch. Have you considered a dc-dc charger with an inbuilt MPPT controller? That would be really nice! Yes, you are on a good track, and it is probably the right track, especially if you are willing to be a bit flexible and tailor your needs to suit the system, rather than vice versa.

Cheers

John

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Follow Up By: Pelikan - Friday, May 17, 2013 at 08:56

Friday, May 17, 2013 at 08:56
Thanks John,

I am pretty sure the Redarc BCDC 1225 has a built in MPPT controller. According to Redarc I should not need the LV model, but I wonder if there is any disadvantage in using that as a belts and braces solution. i.e. if the alternator output is a bit lower than required switching would still be achieved, if the output is high enough to switch then the LV circuit would just be redundant.

Yes we aim to be flexible as this is all experimentation for us.

Cheers, Peter H
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Follow Up By: Member - John and Val - Friday, May 17, 2013 at 09:53

Friday, May 17, 2013 at 09:53
Hi Peter,

Sorry, senior's moment! Yes the BCDC25 does include an MPPT solar controller. I would go with the standard BCDC25 rather than the LV version, as the turn-on voltage of the LV is a bit low for a healthy 12V system and this could be a real nuisance.

Cheers

John
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Follow Up By: Pelikan - Friday, May 17, 2013 at 12:36

Friday, May 17, 2013 at 12:36
Thanks once again to all who replied. This forum is a great source of help.

Cheers, Peter H
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Follow Up By: Member - evaredy - Friday, May 17, 2013 at 17:22

Friday, May 17, 2013 at 17:22
I have a 2012 Dmax and have just gone through something similar.

I wanted to charge a 105ah battery I have in the tray and was told I had a variable voltage alternator and the Ctek unit would not work.
So that left me with Redarc, I was originally going to get the 1225-LV but ended up getting the 1240-LV.

It was discovered that the Dmax does not have a Variable Voltage Alternator, but Redarc had it listed as having one. I was told that the 1240-LV will perform just the same and there will be no problems.

I have had it installed for a couple of weeks now and it is charging the aux battery just fine.
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