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Thread: Trip Report - Lessons learned
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07-24-2021, 11:40 AM #1
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Trip Report - Lessons learned
I am returning from a 2-month trip into the west, visiting Colorado, Utah, Idaho, Montana, South Dakota and Wyoming. We traveled June and July and it was above 6000 ft most of the trip with temperatures mid 90s in the day and low 60s at night.
In preparation, I had changed out my dealer install 12V Interstate marine battery with four 6V AGM, giving me 440 AH capacity (220 AH usable). I installed a DC-DC inverter that had 50 amp charging capacity. The Renogy charger pulls from the truck alternator (4 gauge wire running from the truck battery to the tailgate) when the engine was running. It also has solar port with a MTTP charger. I installed a sub panel to run from a transfer switch on my 2000W DC-AC inverter. This allows me to turn off the coach battery charger and run both outside and inside refrigerators from the inverter while under way. I bought two 100w Renogy solar panels as a science project to test their effectiveness under different conditions. The plan was to install between 8 to 14 panels on the roof after determining what I was going to need. When I sized my batteries, I calculated that I had battery capacity for 3 nights without charging.
What I learned.
1. My calculations sucked. Boondocking in Driggs, ID, my batteries were at 50% each morning when I woke up. The only thing that I did not have direct measurements on was the two desk fans we ran all night in the bedroom. So much for my engineering degree.
2. The Renogy DC-DC inverter knocked it out of the park.
a. When I travelled, it delivered between 450 – 750 watts (maximum of the Renogy) of charge to the batteries, depending on the battery charge state. It ran both refrigerators on 110 AC electric and gave me good range of control with charging the batteries. Typically, I ran both off of the DC-AC 110 AC inverter, but after a night in the rest area, I would put the house refrig on propane and fully charge the depleted batteries as I drove.
b. The savings on propane was significant. Before the inverter, I ran with the house refrigerator on propane. On a trip this long, I would fill my tanks at least once. Wasn’t necessary this trip.
c. Additionally, I ran the truck for 3-4 hours a day to charge the batteries before night, the highest demand time.
3. The solar system experiment provided me with everything that I needed to make a decision. I intentionally created a portable configuration that I could tilt, point, and shade to provide empirical data. My take-away is that for my application, use and mounting configuration, solar isn’t for me. On my roof, it doesn’t work. I plan to travel with a generator, period. A couple of observations.
a. Shade matters big time. Shading a single cell kills the panel. On my roof, if I installed 14 100w panels, 6 would always be partially shaded, which means not operating. I had previously seen a u-tube videos that suggested that but was too skeptical to believe it. The one I remember the most was a 2x4 simulating a sail boom to shade the panel. It is like a switch, generating power to generating no power. That is real and it happens that way. Shade kills the panel output.
b. Tilt angle matters. In Driggs, in the morning (7:00 – 10:00 am), the sun is low in the sky. Even with the panels pointed at the sun and tilted at 45 degrees, the best I got out of two 100w panels was 1 amp, 17 watts. Between 10:00 and 3:00 with the sun overhead, I could point the panels at the sun and do optimum tilt of 30 degrees and it would produce between 5 – 9 amp at 17 volts from the panel (85 – 153 watts). I had expected some derating on the panels but not quite that much.
4. Batteries – AGM or Lithium. I’m not going to touch that third rail. I will say that I’m disappointed with my four 6V batteries that I have. They meets my need for a single over night but didn’t perform nearly as well as I had hoped. That is on me. I didn’t unplug the computer chargers when not used, didn’t regulate the TV, I made pop corn when I wanted, and didn’t bring out the “light” police. Had I not been able to charge from the truck, our Driggs stay at the Balloon Fest would have been terminated.
5. Lastly, never leave home without your generator. I had never planned to size my system to run the air conditioner but did size for bedroom desk fans. Day time temperature were hot falling to 60 at night, however 60 degrees is at 4:00 am not when you go to bed. It was cool at night and we were able to survived without AC.
I’m not throwing water on anyone’s setup or configuration, only my needs and my setup on the Reflection. I can say, solar doesn’t work for me. Everyone has to size for their needs. I do rest areas and occasionally, 3-4 day boondocks. Also, my roof isn’t flat. I have a 10 degree down slope on the back 2/3 of the roof, which is my primary mount area, so performance is going to change with direction of the vehicle. I have the standard protrusions on the roof: 2 AC units, a shower bubble, two fan bubbles and an over-the-air TV antenna. I’ve been on the roof to know that all throw shadows that will kill the adjacent panels for a good part of the day. Based on my configuration and the measurement that I made, I have to derate by 2/3. This accounts for angle, pointing direction, shadows, seasons and panel performance. If I fill my roof, I can get 14 panels, 1400 watts in theory, to yield 500 watts at the batteries. My judgement is too much effort for too little solution. I’m investing into a quiet, quality electric start generator.Bill & Marsha
2020 Reflection 320 MKS
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Not All Who Wander Are Lost
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07-24-2021, 01:15 PM #2
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Well, for our full-time setup, we will have 4 330 watt residential monocrystaline panels, to start with. This is 1320 watts of solar. I will have room in the roof for 2, possibly 3 more. With the residential panels, they are constructed so that even a partially shaded panel so produces electricity. The cheaper panels are designed as parallel cells so, yes, if you partially shaded it, it will not produce power.
The following is a layman's description of the different types of solar components that are out there and won't include a discussion on battery types.
There are several differences that need to be taken into consideration when sourcing solar panels. First is the crystals themselves. There are two types, monocrystaline and polycrystaline. Monocrystaline panels are more expensive and are more efficient. The reason is the crystals are grown in the same direction and have minimal overlap. The polycrystaline panels are less expensive and cheaper to produce. The crystals grow in all directions and thus create less surface area for electrical generation.
There are also several levels of panel wiring types. Most inexpensive panels are wired in parallel, meaning each cell on the panel is wired to the next one and so on. It is easier and cheaper to wire then in this way, however, if one cell is shaded, most likely, the entire panel will stop producing electricity. The other wiring option is series cells. This is more expensive as each cell is wired to the connection point for the panel, so if one, or several cells are shaded, the panel so produces electricity, albeit at a lower voltage and amperage. The final way to wire cells in a panel is a combination of parallel and series, where each line of cells in the panel are wired in parallel, then the rows are wired in series.
Next is your charge controller. There are two different types of charge controllers. PWM and MPPT. Both have their application. A PWM controller draw the current it of the panel at just above battery voltage. A MPPT controller draws current out of the panel at the panel maximum power voltage.
The main benefit of a PWM controller is the power draw from a solar panel or array is approximately 68 watts, regardless of temperature.
The main benefit of an MPPT controller is that it pulls the maximum power from the panel or array at 65° F, however that falls off for every 10° F of temperature increase. So the hotter the ambient temperature is, the less power a MPPT controller will pull from the array.
MPPT controllers are good for that initial "hard push" for charging, to recover what the battery bank lost over night.
PWM controllers are good for a steady charge all day long.
One really must analyze their particular use and situation to make the call on which system components are right for your situation.
Sent from my SM-N986U using TapatalkMark & Mary. Full-timing across the USA (and Canada)!
Current Coach: 2021 Grand Design Reflection 320MKS
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07-24-2021, 05:02 PM #3
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07-24-2021, 06:24 PM #4
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Bah! That is why I shouldn't post something technical and long, from my phone! I'll fix it for clarity.
EDIT: Wait, which part of my post? When talking about the individual cells than make up a panel, series is all wired to the connection point of the whole panel, where parallel is connected cell-to-cell-to-cell-to-connection_point.
Or did I miss something else?
Sent from my SM-N986U using TapatalkLast edited by MoonShadow_1911; 07-24-2021 at 06:26 PM.
Mark & Mary. Full-timing across the USA (and Canada)!
Current Coach: 2021 Grand Design Reflection 320MKS
Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel
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07-24-2021, 06:50 PM #5
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Cell-to-cell-to-cell is series. Parallel would be each cell individually going back to the same central connection point. Most panels are wired as some combination of that, to balance the impact of shading on the panel along with how much voltage you want from each panel. And whether it's standardized or not, most panels I've encountered from 25W up to 340W all have an open circuit voltage in the low 20s, and a max power voltage around 18. Makes it a lot easier to wire them up in parallel even when using different sizes.
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07-25-2021, 07:30 AM #6
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This page explains batteries in series / parallel, yet for solar cells the principle is the same. Series connected would increase the voltage with a somewhat constant current. Parallel connected would keep a constant voltage while increasing current capacity.
https://relionbattery.com/blog/serie...ions-explainedLast edited by Wicked ace; 07-25-2021 at 07:33 AM.
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07-25-2021, 08:27 AM #7
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07-25-2021, 08:46 AM #8
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That is what I've seen also. When you start going to the residential panels, more cells are added in series which increases the output voltage and I have seen some 36 and 48 volt panels. Each cell only puts out about 1/2 volt. Just like batteries, the more cells, the high the voltage. There are serious advantages of using the higher residential voltages to manage IR drops but for what I was going to do with the RV, I couldn't justify the complexity. My "going in" plan was 12 panels, 3 wired in parallel with 12 gauge wire and then bring the 4 groups to a summing point before I penetrated the roof. Again, connecting the grouped panels in parallel but dropping a 1/0 gauge wire to handle the current going to the controller.
Bill & Marsha
2020 Reflection 320 MKS
2018 2500HD Silverado 4x4
Not All Who Wander Are Lost
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07-25-2021, 09:21 AM #9
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To address your post above, you won't find that kind of data in a technical specification. I was able to request the technical engineering document from several of the manufacturers as I was doing research into the efficiency of solar power. Some didn't give me the information. One manufacturer actually granted me an interview with their Sr. Engineer. That was a great insight into solar in general.
Sent from my SM-N986U using TapatalkMark & Mary. Full-timing across the USA (and Canada)!
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07-28-2021, 03:39 PM #10
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I also have 1320 watts then added 630 more with 3 extra smaller panels just for extra capacity because I had room. 6 lithium 105amp lion energy from costco (however i'd by chin or another cheap one now that they exist)
at 2:30 pm i'm pulling in 1200 watts with my mppt controllers with partial shading of A/C's and flat not pointed at the sun and actually tilted away a bit. The key is good panels with diode shut offs and wiring them correctly. my residential panels are split in 2 so even with bad shading half the panel will still produce if the other off isnt. I have my 4 residential panels in a 2S + 2P config and the 3 smaller 210 panels all in series. Panels are cheap now. My 330 rec solar panels are only 212$ each and you can get 350 watt panels for under 175$ now or less even.
you did learn that Lithium batteries are so much better since they can take full power all the time. your Lead acid 6 volt batteries charge in stages which slow down as they get full and take forever thus reducing you solar intake.
I full time and rarely needed a generator and we boondocked for almost 2 months straight. (also added a dc dc charger but only 30 amp) (3K victron multiplus inverter as well)
Bill
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