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Old 04-26-2014, 11:07 PM   #1
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Placement of Solar Controllers

Have a new Portable (folding) 160Wt solar kit... The controllers (2) are on the back of the 2 panels, with about 15' of cable running to the battery clips. Am I misunderstanding, or have I read that to be the most efficient, the controller needs to be within about 3' from the batteries, and what's least important is the run from the panels to the controller... If so, should I remove the controllers from the panels, and put them inside the trailer pass through which "Could" be within that 3' range? IF it's recommended that I move the controllers, what gage of wire should I use from the run from panels to the controllers - ( I'd like about 15-20' )..
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Old 04-26-2014, 11:38 PM   #2
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Depending on your controllers output voltage, and the panels peak voltage, at 160 watts, you may be in the 13.7 volt / 10 amp charging range.

You may not need to move the controllers, although ideally, they should be closer because the voltage from the solar panel is typically higher than the output voltage from the controller

At 10 amps and 15 feet, you should use at least 12 awg wire. Larger is better, like an 8.

From the table below, you can see that at 12 volts, 15 feet and 10 amps, a 12 gage wire will limit your voltage loss to 3%, or about a third of a volt.

At 13.7 volts charging, your loss should keep your voltage above 13 volts.

If we are lucky, mustang65, or one of the electrical wizards will give you some very accurate numbers

If you have a volt meter, you should be able to just measure voltage at the end point.

I guess the point is that you will lose voltage over distance, and small wire. The solar panel should have a higher voltage and therefore can afford to be reduced over this distance, more so that the lower charging voltage, but if your charging voltage is high enough, and good wire size is used, you may not lose that much to warrant moving the controllers
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Old 04-27-2014, 01:43 AM   #3
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The thing is, the charge controller has a voltage value it is trying to charge your batteries to. The voltage coming in to the charge controller must be higher than this by some amount. You lose voltage from one end of a wire depending on how much current is going through it and the size (resistance) of the wire. So if your panels are putting out, say, 16 volts, but you have a long wire run to your controller and lose 5%, you only have 15.2 volts left. Maybe that's okay for your controller, don't know. The more important thing is between the controller and the batteries. The controller is outputting a voltage to charge your batteries. But if you lose 5% there, your batteries don't end up being charged properly.

I'm not sure I agree with the table above. When I try the same numbers in an on line voltage drop calculator I get bigger numbers. I would recommend playing with some values yourself (here's an example of one: http://www.nooutage.com/vdrop.htm). Try to keep your overall loss to 3% max, but things will work best if you keep the loss between controller and batteries as low as you can.
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Old 04-27-2014, 08:20 AM   #4
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Consider as well:

Are you limited to the conductor size where it connects to the controller? On mine, the best I could land was 8awg. ( in and out )

Does the controller allow you to change the charging voltage (up) to compensate for the loss over 15 feet?

Like I suggested, with a volt meter, you can do the math and make the best decision. The online tool from above looks like it's giving you a more accurate answer.

I'll check the source of the table, as a few of the numbers look off.

Hope all this helps
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Old 04-27-2014, 09:32 AM   #5
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Your sure they are controllers on there? OK I had to ask that as all panels have a black box on the back that has nothing to do with the charge controller. IF it is the case the manufacture PROBABLY knows what he is doing when he put them there. IF so I would not over worry about it.
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Old 04-27-2014, 09:50 AM   #6
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Quote:
Originally Posted by Seann45 View Post
Your sure they are controllers on there? OK I had to ask that as all panels have a black box on the back that has nothing to do with the charge controller. IF it is the case the manufacture PROBABLY knows what he is doing when he put them there. IF so I would not over worry about it.
That's a very good point. They may just be wire junction boxes with diodes.
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Old 04-27-2014, 12:01 PM   #7
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One advantage of a portable setup is that you can try it and change things if it's not working well. Not as tough as changing wiring runs inside your camper.
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Old 04-28-2014, 11:10 AM   #8
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Quote:
Originally Posted by ottor View Post
Have a new Portable (folding) 160Wt solar kit... The controllers (2) are on the back of the 2 panels, with about 15' of cable running to the battery clips. Am I misunderstanding, or have I read that to be the most efficient, the controller needs to be within about 3' from the batteries, and what's least important is the run from the panels to the controller... If so, should I remove the controllers from the panels, and put them inside the trailer pass through which "Could" be within that 3' range? IF it's recommended that I move the controllers, what gage of wire should I use from the run from panels to the controllers - ( I'd like about 15-20' )..


Can I ask who the mfr, make and model of the solar panel/controller/kit is, so I can give you a little more info? (Low voltage/high voltage panel?) The reason it is better for the greater distance between the solar panel and charge controller is that there SHOULD be a much higher voltage between them (19VDC (low voltage panel) vs 13-14VDC (Chg controller to battery)), which equates to a lesser voltage/current drop over a longer run. When you look at the output of the solar charge controller you want as much of that power to be sent to the batteries with as little loss as possible.

Check to ensure that you do have a solar charge controller in the charging circuit. You NEVER want to just connect solar panels directly to the batteries without one. That goes into over charging and discharging the batteries, as most low voltage panels do not have blocking diodes built into them and they can drain the batteries when the panels are not producing at least 12 VDC.

Don
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Old 04-28-2014, 01:50 PM   #9
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Purchased them from Solar Blvd - 160wt portable unit came to about $230 with shipping ... Not sure of the Mfgr, may be their own?? Here's some pics ..

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One of the leads connects to a 15' run with Battery Clamps - the other one connects to a Cigarette Lighter adapter.

Guess my question is - is that a 'controller' on the back of the panels, and if so, should I remove it and place it closer to the batteries?
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Old 04-29-2014, 10:14 AM   #10
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I must be blind as I could not find the 80watt panels or the solar charge controller on the website.

Quote:
Originally Posted by ottor View Post
Guess my question is - is that a 'controller' on the back of the panels, and if so, should I remove it and place it closer to the batteries?
For the 15 feet of cable, I wouldn't move the solar charge controller to the battery end of the cable. Should you decide to lengthen the cable between the controller and the batteries, I would then recommend it.

One last thought, do you have the batery clamps protected so that they can not short out if accidently touched?
Just my thoughts
Don
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