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Old 10-27-2020, 04:18 PM   #1
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Solar controller placement

If using the solar on the side most all portable systems have the solar controller near the panel. I know that having a controller closer to the battery reduces power loss. But, is it that significant? On my previous trailer I moved my controller inside the trailer closer too the battery. Just don't know how necessary it is?
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Old 10-27-2020, 04:30 PM   #2
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Voltage drop is merely wasted energy. The closer the controller is to the battery the less loss. That said, with a portable system the charging currents aren't so high that they tax the ability of most solar pre-wire's ability to carry current.

Also need to pay attention to the wire size from solar panels to controller, especially if you have a long extension cord.

One way to squeeze the most power from a portable system is to use an MPPT controller and wire the panels in series. This yields about 40 volts on the input side of the controller which minimizes voltage drop. If the controller is close to the batteries then little voltage drop there.

With an MPPT controller very little power from the panels is wasted where a PWM controller is very wasteful.

My portable solar system has series wired panels, feeds into a heavy #10 ga extension cord, then feeds the MPPT controller that's less than 2 feet from the batteries. Charge current in full sun is around 11-12 amps which isn't all that bad considering the panel's are only 160 watt total.
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Old 10-27-2020, 04:42 PM   #3
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The output of the panels is usually higher than what you want to use to charge the battery. This allows for any loss between the panel and the controller. The controller delivers the proper levels to the battery charge wires so you want to minimize any losses between the controller and the battery as there is no easy way to compensate for that loss.
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Old 10-27-2020, 04:51 PM   #4
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Got it. But my question is, is the drop that significant???.
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Old 10-27-2020, 06:29 PM   #5
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Got it. But my question is, is the drop that significant???.
If the loss is greater than 2% that's significant. Then again, a loss is a loss.

Most controller terminals will accept #10 awg wire so why not just add a couple of short pieces.
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Old 10-27-2020, 06:51 PM   #6
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I'm Using 10awg. But, your answer is what I'm looking for. Is the loss 1,2,5% etc.. Not sure if anyone has calculated it. I just assume it must not be all that great or manufacturers would not attatch controllers to panels. They could just as easily tell you to hook up the controller near the battery.
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Old 10-27-2020, 07:26 PM   #7
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TitanMike: What brand of panels do you have that put out that kind of amperage? Most panels at 160 watts will produce just under 9 amps at best.
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Old 10-27-2020, 08:03 PM   #8
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I have an acopower 105w solar panel kit with 10amp controller. Used it on my Casita. As stated moved the controller from panel to near battery in trailer. On new e pro 19fd trailer trying to decide if the loss is worth the effort of doing the rewiring
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Old 10-27-2020, 08:29 PM   #9
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TitanMike: What brand of panels do you have that put out that kind of amperage? Most panels at 160 watts will produce just under 9 amps at best.
Most portable panels are wired in parallel and use a pwm controller.

Mine are two Komaes 80 watt panels wired in series and feed into a Victron 75/15 MPPT Smart controller.

I'm harvesting the power thats wasted in a parallel/pwm setup.
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Old 10-27-2020, 08:43 PM   #10
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The acopower is to be used to supplement thr 190w of solar on my roof. I have 2 6v batteries. On the Casita the acopower had no problem keeping my batteries charged up. my issue now will be to keep batteries up while running a dc fridge with the total of 295w of panels.
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Old 10-27-2020, 11:47 PM   #11
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The acopower is to be used to supplement thr 190w of solar on my roof. I have 2 6v batteries. On the Casita the acopower had no problem keeping my batteries charged up. my issue now will be to keep batteries up while running a dc fridge with the total of 295w of panels.
That will depend on how much sun reaches the panels and the other loads placed on the batteries.
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Old 10-28-2020, 06:04 PM   #12
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Here is a response I got to this question on the acopower website: Since the controller senses voltage and any length of cable will involve some voltage drop it would probably reduce the output of the panel, maybe significantly. Even the cable from the controller to the battery will have voltage drop and reduce the charging capability. The shorter and heavier gage the cable the better. A few tenths of a volt can make a considerable difference. in the charge rate. A half volt drop in the whole system will cause a significant loss of charging ability." So, to answer my question it appears that the drop would be significant according to this response.
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Old 10-28-2020, 07:53 PM   #13
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Here is a response I got to this question on the acopower website: Since the controller senses voltage and any length of cable will involve some voltage drop it would probably reduce the output of the panel, maybe significantly. Even the cable from the controller to the battery will have voltage drop and reduce the charging capability. The shorter and heavier gage the cable the better. A few tenths of a volt can make a considerable difference. in the charge rate. A half volt drop in the whole system will cause a significant loss of charging ability." So, to answer my question it appears that the drop would be significant according to this response.
I believe this was mentioned earlier.

To quantify the voltage drop you might want to use this calculator. Just enter the total ROUND TRIP wire length from controller to batteries. Use 8 amps for the amperage. The calculator will show the voltage drop for each wire size and by adjusting length up or down you can see the difference in voltage drop due to length.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html
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Old 10-28-2020, 08:01 PM   #14
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Sweet, thanks.
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