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Old 01-14-2020, 05:12 PM   #1
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Adding portable solar to rv with mounted solar

I am probably over thinking this, but what is the best way to connect a portable solar kit to a travel trailer where I have 300w solar on the roof with 40amp mppt charge controller?

Do I connect the portable to the charge controller PV in (with the lines from the roof mounted panels) or just use it like it was designed and connect it to the batteries directly?

I'm thinking it would be better to add it to the input of the charge controller so I get a total input higher, rather than it essentially working against each other since both would be supplying current.
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Old 01-14-2020, 05:17 PM   #2
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You'd be good either way. If the existing controller and the portable kit controller are doing their thing they'll figure it out. The batteries can only hold so much amperage and they'll both ramp up or cut back rate of charge as necessary. As I understand charging from multiple sources.
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Old 01-14-2020, 05:28 PM   #3
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they'll both ramp up or cut back rate of charge as necessary. As I understand charging from multiple sources.
that is what I want to avoid. I want to increase the total pushed to the batteries, not have one thinking the batteries are full because they are being charged by another source. And this may not be the way it works, it may just be my misinformed understanding.
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Old 01-14-2020, 05:35 PM   #4
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If either charge controller thinks they're full, they're probably full. So it doesn't matter which one decides.
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Old 01-15-2020, 08:04 AM   #5
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I have 3 MPPT controllers connected to different panels on my roof. I have a 4th MPPT controller for a 300 watt portable array. They all connect to my system and work together with out issue.
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Old 01-25-2020, 08:38 AM   #6
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I just spliced the wires from the new panels into the line before it went to the charge controller. I used a 10 gauge sidewall port and wires. Your charge controller should be able to handle another 200-300 watts.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 01-27-2020, 05:59 PM   #7
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You'd be good either way. If the existing controller and the portable kit controller are doing their thing they'll figure it out. The batteries can only hold so much amperage and they'll both ramp up or cut back rate of charge as necessary. As I understand charging from multiple sources.

Are you saying that piggybacking 2 controllers is ok?


Can hand scribe and post a simple diagram?



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Old 01-29-2020, 11:56 AM   #8
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Are you saying that piggybacking 2 controllers is ok?


Can hand scribe and post a simple diagram?

Jim58
Yes, I have 2 charge controllers. One runs 476 watts of panels, the other runs 400. The wires meet just before going to the batteries.

Draw your diagram on paper then photograph it to post it here.
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Old 02-05-2020, 06:49 PM   #9
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Yes, I have 2 charge controllers. One runs 476 watts of panels, the other runs 400. The wires meet just before going to the batteries.

Draw your diagram on paper then photograph it to post it here.
So you just ran both in parallel. That I can see. It sounded like you suggested it would be okay to feed a controller output (portable unit) right into another controller.
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Old 02-06-2020, 08:55 PM   #10
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So you just ran both in parallel. That I can see. It sounded like you suggested it would be okay to feed a controller output (portable unit) right into another controller.
Yes, the black wire from the second controller attaches at the shunt, the red just before the fuse on the line that leads to the positive battery terminal. Having the sidewall port makes it easy.

My apologies for not making that clear.
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Old 02-06-2020, 09:19 PM   #11
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To rbTN - I don’t see that you mentioned if you are adding just extra panels or panels that have their own charge controller. Also, how many watts are you adding?

Your 40 watt MPPT charge controller may be able to support the extra panels. I have 2 PSM charge controllers - a 20 amp with 200 watts and a 30 amp with 472 watts.
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Old 02-07-2020, 05:06 PM   #12
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okmunky - I didn't have an exact plan, just was thinking about if the spot I have does not get a lot of sun how to supplement the roof mounted with a portable set up.

I've done more reading and it sounds like the most common solution is to have a controller for the portables which makes even more sense to me now since it would provide full redundancy of the charge system.

I was weighing options as to what to add, more installed or portable, and how much but I have decided to see how the system does before I proceed further.
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Old 02-07-2020, 06:14 PM   #13
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Ok, I get it now. I have 200 watts of unattached panels because where I park in my daughter’s Seattle area backyard trees shade the roof panels most of the day.

You don’t need to buy expensive plug in panels with an attached charge controller. Just add an additional controller sized for the extra panels.
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