solar connections

Hi All
I have 2 100amp hour batteries connected to a
C TEK D250S Dual DC 12V Battery Charger 20A Solar Controller in my camper trailer that i currently charge when i am hooked up to my car through an Anderson plug, what i would like to know is can i connect my solar panels that have an mppt controller connected to them straight into the Anderson plug on my trailer and go through the C TEK controller or do i have to disconnect it and charge straight to the batteries.
Thanks Bill
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Reply By: Cravenhaven - Monday, Apr 15, 2013 at 15:52

Monday, Apr 15, 2013 at 15:52
It is always best to have the charge controller as close to the batteries as possible. The MPPT controller on the panels is at the wrong end of the connection wire for most efficient use.
I would have thought that the best way to connect was to bypass the controller on the panels and connect the solar panels directly to the solar input on the D250S. That way the D250S will direct charge back to the car battery if the camper batteries are already fully charged. I think the D250S already has an MPPT controller built in.
The next best configuration is to move the MPPT controller from the panels to the battery and run the long connection wire between the panel and the controller.
The least favourable way is to just connect the existing output of the MPPT directly to the batteries.
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Follow Up By: Notso - Monday, Apr 15, 2013 at 16:07

Monday, Apr 15, 2013 at 16:07
The 250s Dual does have a built in MPPT controller.
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Follow Up By: feno60 - Monday, Apr 15, 2013 at 16:38

Monday, Apr 15, 2013 at 16:38
Will it matter if i don't take the controller of the solar panel and still go through the C TEK
Bill
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Follow Up By: Member - Frank P (NSW) - Monday, Apr 15, 2013 at 16:59

Monday, Apr 15, 2013 at 16:59
Yes, Bill, it will matter. Neither black box will work properly.

If you continue to use the controller on the back of the panels you should connect direct to the battery.

Cheers
FrankP

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Follow Up By: Member - Frank P (NSW) - Monday, Apr 15, 2013 at 17:08

Monday, Apr 15, 2013 at 17:08
Bill,

Further to that, if you wish to use the Ctek you should bypass the MPPT on the back of the panels, for the same reason, and connect directly to the solar input on the Ctek. The choice is yours. I think I would use the Ctek.

Cheers
FrankP

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Follow Up By: Ross M - Monday, Apr 15, 2013 at 17:08

Monday, Apr 15, 2013 at 17:08
If you are going to connect to the Ctek then it will be necessary to bypass the MPPT's on the panel's as it's pulsing and sensing output is not a form of power delivery the Ctek will like to see.
The MPPT's on the panels means you have the regulator at the maximum distance from the battery and it then has the cable run as a resistance between it and the battery it is trying to sense the voltage of. Not the best situation.

Both styles of regulator like to see clean DC input, not something which is on and then off and also trying to sense voltage levels.

If the solar is connected to the Anderson and using the Ctek, then it can't be also connected to the vehicle battery at the same time, if the panel regs are bypassed.

You have a number of possible connections and operational configurations here and there are many explanations to try and cover all possible situations.
After you decide which way it will be used then people can more accurately determine their advice.

Ross M
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Follow Up By: feno60 - Tuesday, Apr 16, 2013 at 07:23

Tuesday, Apr 16, 2013 at 07:23
Thanks everyone for your input
I will only be using the solar when the trailer is not connected to the vehicle so it looks like I will disconnect the controller on the solar panel.
Cheers Bill
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Reply By: Member - Nolo (Brisbane) - Tuesday, Apr 16, 2013 at 07:57

Tuesday, Apr 16, 2013 at 07:57
From what you say the MPPT controller is attached to the panel. The normal output is then regulated. You could add a short connection to where the solar goes in to the MPPT controller and with an extension lead (with anderson plug connections) connect this to your camper trailer anderson plug. This would then deliver raw solar voltage direct to the C TEK.

Regards
AnswerID: 509111

Reply By: Member - John and Val - Tuesday, Apr 16, 2013 at 09:06

Tuesday, Apr 16, 2013 at 09:06
BIll,

Theres a whole lot of good stuff tangled up in the above, and also some not-so-good.

The short answer to your question is No, plugging the output of your solar controller/s into the line coming from the engine bay will NOT work. Why? 1. The controllers need direct access to the battery/s to judge their state of charge and their charging requirements. 2. The D250S will get confused by the signal coming from the controllers.

The best solution is, as suggested above, to disconnect the on-panel controllers, and feed the raw panel output to the D250S solar input. The D250S should be mounted close to the battery/s and will take care of all charging. (It will NOT send any excess back to the vehicle battery as has been suggested.)

Cheers

John
J and V
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Reply By: scandal - Tuesday, Apr 16, 2013 at 16:26

Tuesday, Apr 16, 2013 at 16:26
Adding to what has been said, the ctek unit can only handle 25 volts, make sure the panel(s) are wired parallel, my panels put out 18-21 volts each.
My panels are portable, I have cut the wires before the in built controller (which was a PWM unit) I also put in an anderson plug and slightly heavier cable with another anderson plug feeding into the solar terminal on the ctek, by doing this I utilise the MPPT controller for charging the camper battery (primary use for the solar panels), but also have the ability the plug the panels back into the inbuilt control unit to be able to charge a battery that's not controlled by the ctek using the same wire but with some alligator clips via anderson plug.
This way my solar panels are mainly used for the camper battery, but can be used to charge the vehicle battery if needed.
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