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Old 09-12-2021, 01:28 PM   #1
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Adding solar this simple?

Just from a wiring perspective, it seems adding solar is fairly simple. Am I missing anything?

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Add 2x200W panels and 40A MPPT charge controller:

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Old 09-12-2021, 01:55 PM   #2
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Just from a wiring perspective, it seems adding solar is fairly simple. Am I missing anything?

That's it. Electrically, adding solar is that simple. However, I'm not sure why you are connecting your panels in series. Connecting the panels in parallel will provide greater current (amps) potential.
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Old 09-12-2021, 01:58 PM   #3
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That's it. Electrically, adding solar is that simple. However, I'm not sure why you are connecting your panels in series. Connecting the panels in parallel will provide greater current (amps) potential.
That's what the Rich solar site that I bought the system from recommends. Would parallel be better for my situation?

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Old 09-12-2021, 02:18 PM   #4
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That's what the Rich solar site that I bought the system from recommends. Would parallel be better for my situation?

The length of the wire run from the panels to the controller will help you decide parallel or series wiring. They both have good and bad but if you’ve got a long run, go with series and an MPPT controller because the wire can be smaller gauge.
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Old 09-12-2021, 02:19 PM   #5
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The length of the wire run from the panels to the controller will help you decide parallel or series wiring. They both have good and bad but if you’ve got a long run, go with series and an MPPT controller because the wire can be smaller gauge.
The run from the panels to the controller will be 14 ft. one way. The kit comes with 10ga wire. Seems that combo would work better with series panels to keep the amperage lower.
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Old 09-12-2021, 02:35 PM   #6
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The run from the panels to the controller will be 14 ft. one way. The kit comes with 10ga wire. Seems that combo would work better with series panels to keep the amperage lower.
I agree.
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Old 09-12-2021, 02:50 PM   #7
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That's it. Electrically, adding solar is that simple. However, I'm not sure why you are connecting your panels in series. Connecting the panels in parallel will provide greater current (amps) potential.
Yes and no. The current produced at the output of the solar controller is what counts and that current is the same regardless of the current coming from the panels. What matters is the power coming from the panels. One can have 20 amps at 18 volts (parallel connection) or 5 amps at 72 volts (series connection). In either case, the power is 360 Watts. In both cases the solar controller will provide about 26 amps to the battery (in this example and assuming a 95% efficient solar controller).

There are myriad arguments for going parallel or series, but often the smaller wire and lower wire losses (heat) of the series connection wins. Going series does require a solar controller that can handle the higher voltage. Most solar controllers are slightly less efficient with the higher input voltage of a series connection (95% vs 96%) which tends to offset the wire losses of a parallel connection though the ability to use smaller wire remains.
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Old 09-12-2021, 03:00 PM   #8
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The run from the panels to the controller will be 14 ft. one way. The kit comes with 10ga wire. Seems that combo would work better with series panels to keep the amperage lower.
I agree. Shade resistance tends to favor parallel, but most other considerations suggest series. One that is often overlooked is that with the higher voltage of a series connection, the MPPT controller has more "room" to eke out extra power early and late in the day or when it's semi-cloudy. With, say 18V max sun working voltage of a parallel array, the MPPT controller can bring the voltage down to only about 16V to increase power with weak sun. That doesn't help much. With four panels in series, the voltage would start at 72 volts and the MPPT controller can bring that down to 16 volts (4 volts per panel) to eke out more power.

I've never tried to determine how much more energy one gets with the higher voltage of a series array, but I've watched my controllers pull voltage ever lower as the sun wanes, using the whole range from 72V down to 16V.
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Old 09-12-2021, 03:09 PM   #9
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That's what the Rich solar site that I bought the system from recommends. Would parallel be better for my situation?


Probably best to stay with their recommendation which includes a MPPT controller and makes good use of lighter gauge wire. The only negative point I can think of might involve a shadow cast upon one panel which would reduce the efficiency of the other panel. In a parallel configuration a shadow on one panel has no affect on the other panel. However, in the reality of the mobile RV world, I am not sure what merit the shadow debate has since were always moving around.
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Old 09-12-2021, 03:15 PM   #10
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I agree. Shade resistance tends to favor parallel, but most other considerations suggest series. One that is often overlooked is that with the higher voltage of a series connection, the MPPT controller has more "room" to eke out extra power early and late in the day or when it's semi-cloudy. With, say 18V max sun working voltage of a parallel array, the MPPT controller can bring the voltage down to only about 16V to increase power with weak sun. That doesn't help much. With four panels in series, the voltage would start at 72 volts and the MPPT controller can bring that down to 16 volts (4 volts per panel) to eke out more power.



I've never tried to determine how much more energy one gets with the higher voltage of a series array, but I've watched my controllers pull voltage ever lower as the sun wanes, using the whole range from 72V down to 16V.
I have two 100 watt panels wired in series feeding an MPPT solar controller. In full sun I have recorded as much as 210 watts being produced by this system.

Parallel systems with PWM are far less efficient. PWM controllers will deliver 55-75% of the power available.

Portable systems wired in series and using MPPT controller may well outperform flat roof panels stuck in the shade.
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Old 09-12-2021, 03:15 PM   #11
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The run from the panels to the controller is fairly straight forward. The black tank vent comes through the roof right where I am putting the 2 panels. That goes straight down to my power panel area in the 5er and it's 4 ft to the controller. The controller will sit right next to the batteries and I'll need about 1 ft of 6ga wire from the controller to the battery busses.

I may add another 2x200W panels in the future, but I'll deal with that then. The run is easy to get to so changing wires later is easy.
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Old 09-12-2021, 03:19 PM   #12
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I have two 100 watt panels wired in series feeding an MPPT solar controller. In full sun I have recorded as much as 210 watts being produced by this system.

Parallel systems with PWM are far less efficient. PWM controllers will deliver 55-75% of the power available.

Portable systems wired in series and using MPPT controller may well outperform flat roof panels stuck in the shade.
I do have a Furrion connector on the side of the trailer that I could use for additional portable solar. I have it wired with 8ga wire and it's a 6 ft run to the batteries.
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Old 09-12-2021, 03:25 PM   #13
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Wow! … looking at the photo of your roof. You've got a wonderful space for lots of solar panels. Makes me jealous – I had trouble finding space on the roof of my 25-ft Prism for two panels. I expect you'll be very pleased with your project when done. Hope you post photos of the finished project. Good luck!
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Old 09-12-2021, 05:13 PM   #14
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WRT series vs parallel, check your charge controller specs against your solar panel open circuit specs. Also, solar panels often put out a bit higher voltage in cold weather.
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Old 09-12-2021, 05:21 PM   #15
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I do have a Furrion connector on the side of the trailer that I could use for additional portable solar. I have it wired with 8ga wire and it's a 6 ft run to the batteries.
That would certainly be a worthwhile addition if you tend to park the trailer in shade.

With my smaller trailer I use portable panels as my only solar power source. Series connected and feeding an MPPT controller provides plenty of power for my needs although some winter camping trips might require use of the generator every other day to make up for the furnace draw.
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Old 09-12-2021, 06:16 PM   #16
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I have two 100 watt panels wired in series feeding an MPPT solar controller. In full sun I have recorded as much as 210 watts being produced by this system.
Was that 210W a "hole in the cloud" situation? Where you get strong direct sun via a hole in the clouds plus a lot of diffused light from the clouds around that hole. I once got 635 Watts from 600W of panels in this situation though being at 7500 feet elevation and it being cool out helped.
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Old 09-12-2021, 06:24 PM   #17
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Was that 210W a "hole in the cloud" situation? Where you get strong direct sun via a hole in the clouds plus a lot of diffused light from the clouds around that hole. I once got 635 Watts from 600W of panels in this situation though being at 7500 feet elevation and it being cool out helped.
Was just a nice sunny day each time I recorded over 200 watts.

I will say that I had given the panels a good cleaning each day this occurred. Amazing how much crud a white paper towel will show when cleaning with Windex after a few days of accumulating crud from the air.

I will say that portable panels are a lot easier to keep clean than rooftop mounted
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Old 09-12-2021, 06:25 PM   #18
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....... "With four panels in series, the voltage would start at 72 volts and the MPPT controller can bring that down to 16 volts (4 volts per panel) to eke out more power." .........
The above may not be clear ... the 72 volts is mentioned in the context of operating voltage and MPPT action, not open circuit voltage. When it comes time to choose a solar controller or check the capability of your solar controller, the voltage of concern is open circuit voltage which for the panels that operate at around 18 volts is 24 volts. So four panels that provide 24V open circuit would need a controller that can handle 100 volts from the panels.
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Old 09-12-2021, 06:35 PM   #19
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.......... I may add another 2x200W panels in the future, but I'll deal with that then. The run is easy to get to so changing wires later is easy.
Indeed. You likely will joint the upgrade club if you boondock a lot (DW and I are 100% dry/boondocking and no longer even have a way to plug the RV into an outlet). After my second upgrade I had 400W. I then upgraded to 600 (6x100) and added a second controller with 300 on each. Then added 400W (2x200) and a third controller. I have 2 kW of panels in the garage that will replace the six 100's and add three 200's that combined with the two 200's will give me 2200W. I won't do this until I have the mini split (also sitting in the garage) and can use it.

But, the point I was heading for in the next above paragraph is that I now have three pairs of #10 solar wire running up alongside my tank vent pipe and potentially two more in the future (and a total of four solar controllers).

That is a very tempting roof ..... I can see 2 kW in your future.
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Old 09-13-2021, 12:43 PM   #20
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That's what the Rich solar site that I bought the system from recommends. Would parallel be better for my situation?

I have considerable experience with solar panels. What you need to know about series vs parallel:
- downside of parallel: You have to get above 15 volts before the charge controller turns on. Your panels start at 0 volts in the dark and ramp up to about 18-20 volts in full sun so you will get zero output before 10 AM or after 4 PM or if it is cloudy. By wiring in series, the voltages from the 2 panels add so your charge controller will turn on early in the morning until late evening and will produce even in heavy cloud cover.
- downside of series: Think of a water hose with 2 taps. If either tap is closed you get no water. IE if one panel is in the shade and the other is in full sun, you output is limited by the one in the shade. In the places we tend to camp, it is almost guaranteed that one side of our trailer is always in the shade.



The ideal layout for an RV (in my opinion) is 4 panels. 2 in series on each side of the roof then the pairs connected in parallel.
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