Question re DC to DC charging in a Jayco caravan

Submitted: Sunday, Feb 23, 2014 at 13:59

ThreadID: 106379 Views:9352 Replies:3 FollowUps:9

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Gavin M2

I have just bought a 150W solar panel to fit on my 22' Jayco Starcraft and I'm currently researching solar regulators/controllers.

I quite like the idea of using the "CTEK D250S Dual" and killing two birds with one stone - i.e. enhancing the caravan battery charging using the CTEK's DC-DC charging capability and, at the same time, regulating the solar power via the CTEK's MPPT capability.

What I'm scratching my head about is where a DC-DC charger is connected into the Jayco caravan wiring - before or after the Power Supply Unit (PSU)?

The wiring in my caravan goes - trailer hitch > PSU's DC inputs > PSU's Batt +ve & -ve outputs > battery.

As the PSU "provides full battery management" being a four stage charger itself, I do not want to upset the system by introducing another charger incorrectly.

Anyone used a DC-DC charger with a Jayco?

All advice appreciated.

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Reply By: Dennis Ellery - Sunday, Feb 23, 2014 at 18:11

Reply By: Sand Man (SA) - Sunday, Feb 23, 2014 at 22:16

Sunday, Feb 23, 2014 at 22:16

The Ctek D250S dual would replace the PSU you currently have. You would compromise the integrity of the charging circuit if you have more than one battery management system.
The DC-DC charger has dual input ports (alternator and solar) and both can be connected at the same time if you have a permanently mounted solar panel. The D250S will determine which is the better input source at any one time and switch to that port. It also provides a multi-stage battery management system, so you don't need the PSU currently installed.

Just remember, you will need to bypass any built-in solar controller on the solar panel array if it has one.
I opened the junction box on my folding portable solar panel and added a separate cable direct from the terminal strip (bypassing the on-board controller) and terminating on the lid of the junction box with an Anderson connector.
I simply plug in a patch lead and run this to the D250S Dual charger mounted in the camper trailer.
I made a short lead of suitable cable from the solar panel port terminals to an Anderson connector mounted at a convenient place on the Camper and connect the panel to the solar port with a patch lead (Anderson connectors each end)
The original cable (terminated with a merit plug) can still be used to connect the solar panel to my vehicle's auxiliary battery, if I need to charge it, employing the on-board solar panel controller.

This setup works for me very well.

Bill

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Follow Up By: Nomadic Navara - Monday, Feb 24, 2014 at 00:26

Monday, Feb 24, 2014 at 00:26

The D250S does not replace the Setec. The setec is powered from the mains. You still need that for charging when on mains power and there is little sunlight. Dennis Ellery gave you the correct info, hw has a Jayco and knows what he is doing.

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Follow Up By: Sand Man (SA) - Monday, Feb 24, 2014 at 07:32

Monday, Feb 24, 2014 at 07:32

Ah,
My apology for misunderstanding what the PSU unit does.
I also have a separate mains charger connected but only used at home or the rare occasions we stay at a powered site.
Totally agree with what Dennis and you have said.

Bill

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Reply By: Member -Dodger - Monday, Feb 24, 2014 at 15:03

Monday, Feb 24, 2014 at 15:03

I have done the same as Dennis.
So far in 4 years there has been no problem with the electrics in our Jayco.

The Setec as fitted by Jayco charges the battery whilst on 240v. and the 250s DC 2 DC charger takes care of the 12v from panel and car, just connect directly to battery.

I used to have a handle on life, but it broke.

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Follow Up By: Gavin M2 - Monday, Feb 24, 2014 at 22:58

Monday, Feb 24, 2014 at 22:58

Thanks Doug. What size solar panel/s are you running with the D250S?

I'm keen to use it but think my power requirements may exceed its 20A capacity. I only have one 150W panel at the moment but would like to add another down the track. Short circuit current on my panel is 9.7A so if I add another identical panel and allow for the required additional 25% I'll be up to 24.25A (9.7A x 2 x 1.25) exceeding the D250S's rated capacity. I may have to go for a 30A regulator.

Gavin

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Follow Up By: Nomadic Navara - Tuesday, Feb 25, 2014 at 00:03

Tuesday, Feb 25, 2014 at 00:03

Gavin, it does not matter if the size of the panels will mean they are capable delivering more current than the rated output of your D250S. The charger will only accept sufficient current from the panels to produce its full output. That is exactly the same situation as the input from the alternator, the charging circuit will only take sufficient current from it to drive it to its full capacity.

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Follow Up By: Gavin M2 - Tuesday, Feb 25, 2014 at 02:10

Tuesday, Feb 25, 2014 at 02:10

Thanks Peter. Now I'm a little confused.

I read on the "Solar Online" website here under "Solar Regulator Sizing Information" this advice:-
"Solar regulators often short the solar panel input when regulating. This does not damage the solar panel but it does mean that the solar regulator must be sized to handle 125% of the solar panel's rated short circuit current".

Am I missing something here?

Gavin

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Follow Up By: Nomadic Navara - Tuesday, Feb 25, 2014 at 08:56

Tuesday, Feb 25, 2014 at 08:56

Gavin, there are two types of regulator, the shunt and the series pass types.

Most of the regulators commonly used these days are the series pass type. Both the PWM and MPPT work on the series pass principle.

The original regulators employed the shunt principle. Back in the 60s and 70s high current transistors were just being developed. If they were used in the series pass circuitry they had too much voltage drop across them and thus wasted too much power. You thus used large banks of them to 'shunt' the output of the panels to prevent the batteries terminal voltage from rising to a dangerous overcharging situation. These regulators are still used with wind turbines where you need to keep a load on the generator.

The D250s does not work on the shunt principle. It would have a large heat sink to dissipate the power if it was a shunt type.

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