Coast Resorts Open Roads Forum: Tech Issues: not another solar question ??
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 > not another solar question ??

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wanderingbob

monticeeo, fla

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Posted: 12/02/22 10:17am Link  |  Quote  |  Print  |  Notify Moderator

As I pull several different trailers I am considering mounting one of those Renology 400 watt packages on my pickup topper instead of on the trailer . Where would you put the controller , in the truck topper or in the trailer near the batteries . The distance the wires would be routed would be less than 10 feet .Is this a stupid idea ?

12thgenusa

Loveland, Colorado

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Posted: 12/02/22 10:54am Link  |  Quote  |  Print  |  Notify Moderator

Mount it such that the controller stays connected to the batteries when the panels are disconnected, otherwise the controller can be damaged. Or have a means of disconnecting the panels first and reconnecting the batteries first.


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ktmrfs

Portland, Oregon

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Posted: 12/02/22 10:58am Link  |  Quote  |  Print  |  Notify Moderator

controller should be as close to the batteries as possible, especially if it is a MPPT controller.


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KD4UPL

Swoope, VA

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Posted: 12/02/22 03:22pm Link  |  Quote  |  Print  |  Notify Moderator

I'd put the controller in the truck, that way you only need one instead of in each trailer. I'd connect the output of the controller to the charge line going to the 7 pin on the truck. If you're not towing a trailer it will keep your truck battery charged up. If you are towing a trailer it will keep your trailer battery charged up.
To make this work your charge line has to be hot all the time like on a GM truck, not switched off with the ignition like on a Ford. SOME charge controllers can be damaged if the panels are hooked up with no batteries.
Also, you will need to have very similar batteries in all your trailers and truck or you will have to be changing the absorb and float settings on the controller for each trailer. If they are all flooded or all AGM of similar brand it should work fine.

pianotuna

Regina, SK, Canada

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Posted: 12/02/22 04:55pm Link  |  Quote  |  Print  |  Notify Moderator

Shop around for better prices.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Bobbo

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Posted: 12/02/22 05:15pm Link  |  Quote  |  Print  |  Notify Moderator

The closer the charge controller is to the batteries, the more efficient it is. Distance from the PV (solar panel) is less critical.


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ktmrfs

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Posted: 12/02/22 07:48pm Link  |  Quote  |  Print  |  Notify Moderator

Bobbo wrote:

The closer the charge controller is to the batteries, the more efficient it is. Distance from the PV (solar panel) is less critical.


true for MPPT controllers, somewhat true for PWM controllers.

With a PWM controller if the battery is deeply discharged it lets full panel current to the battery and voltage is regulated by the battery and internal resistance. Where the controller is really doesn't have much if any effect on charge current. As the battery nears full charge it switches to a duty cycle square wave, and here is where distance matters since now voltage drop between the controller output and battery will limit charge current and increase charge time needed for a full charge.

For a MPPT controller it sets the voltage at the output of the controller during the entire charge so voltage drop in the line working against battery voltage and internal resistance= low charge rate. And since MPPT controller output current is higher than input current during initial charge, voltage drop between the controller and battery can be more limiting than between the panel and controller. Especially true if the input to the controller is a series string of panels. So for a MPPT controller it is important to have the controller as close as possible to the batteries.

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