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re RJCarter3
[What I would do is buy one of the flexible panels that you can roll up and store away. ... . You can reposition that panel several times a day for maximum power generation]
That is what we did with our 2019 1500 LR, used as a weekender, and it works very well ... We have three 200 watt panels, each has four 50 watt panels that fold out (and fold up), just as easy as a beach folding chair, and when folded fit very compactly inside the van under the bed.
 

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Discussion Starter · #23 ·
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re RJCarter3
[What I would do is buy one of the flexible panels that you can roll up and store away. ... . You can reposition that panel several times a day for maximum power generation]
That is what we did with our 2019 1500 LR, used as a weekender, and it works very well ... We have three 200 watt panels, each has four 50 watt panels that fold out (and fold up), just as easy as a beach folding chair, and when folded fit very compactly inside the van under the bed.
How do you hook it up to the battery?
That seems like a good idea. Just there's REALLY not much space left under the bed. Definitely not enough space for a folding chair. I might be able to shuffle stuff around a bit but it's pretty well tetrised in right now.
 

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Since your solar produces almost 60V at less than 8Amps may I assume you wired your panels in Series? To my previous comment I wonder if series is more advantageous than parallel in the winter since lithiums need Volts more than Amps? Is that correct?

Edit: it probably should say that a MPPT needs a certain amount of Volts before it starts charging?
Hi @MaggieMarty

I wired 6 - 100W panels; 2 parallel of 3 series so max 10amps @ 60v.

I choose the Victron 100 | 50 MPPT controller ( typically need 5volts above battery voltage - so 12.5v plus 5 = 17.5volts). The 100 is max volts it can take from the panels & the 50 is the max amps it can send to the batteries. The Victron is very user programable.

The advantage of series & parallel has to do with “what type of sunlight” I am harvesting from. I suppose “seasons” can have something to do with that, but really it comes down to a multitude of parameters IMO. I also think a bit of trial & error helps one sort thru the parallel & series question. If I had solar on a van roof, I would design it so I could easily alter the series/parallel combinations & allow for the wire size of parallel (highest amperage configuration).

FYI; Sept 6th I got 600W out of my 600W panels (roughly 60volts @ 10amps);

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Hi @MaggieMarty

If I had solar on a van roof, I would design it so I could easily alter the series/parallel combinations & allow for the wire size of parallel (highest amperage configuration).
That’s exactly my plan. I have 4 x 100W panels and am starting with 2 parallel of 2 series for now for the reasons I wrote to @aaronmcd earlier. I think it might be the best of both worlds, harvesting earlier in the day and longer in the afternoon, or with a lower sun angle. I can change my configuration in 15min if I have to.
 
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Solar dependent on weather: current use has been low angle but mostly sunny. A cloudy day here and there. No / not much heater use. In colder weather I'd use the propex more, but the fan and fridge less.

A bigger battery bank would only be helpful if I can charge it up on the weekends. I'm not sure yet of our "normal" driving habits. The first couple weeks were a lot of driving just to see as much as possible on our way from north SF Bay Area to Phoenix area. Here in AZ, the weekend only put back ~100Ah. After the holidays, we might drive more on the weekends, but maybe not 300Ah of driving.

Also a solar panel is easier and cheaper to add. I don't have space for another battery, don't have my hammer crimper with me, would have to move stuff around and make new cables.

I currently have 2x200 monocrystaline Renogy panels in parallel, and a 40A Renogy MPPT charge controller. Since it's physically impossible to get all the power out of horizontal panels north of the tropics, I figure I can put up to 600W up there with the 40A controller.
Yup a bigger battery bank still needs to be charged - may or may not help you

I am not familiar with the 40A Renogy, but if it can handle your panels in “series” & you panel connectors are long enough, you could try that for zero dollars. Your panels have “specs” & so does the MPPT charger/controller.

Like you say, adding another 200W panel might help. The “magic” might be in series config rather than parallel. In my case when the sun rises my voltage is quickly up to charging volts “around 18volts” right after dawn & even though the amount of watts might not be large it is on the positive side of the equation.

Solar is all about the harvest, which waters down to the equipment & configuration. No sun no harvest.

Alternator, Solar, Shore Power, or Generator; is there another method to charge? We primarily used the PM alternator & sometimes (rarely) a Honda generator (2200W) when not moving.
 

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That’s exactly my plan. I have 4 x 100W panels and am starting with 2 parallel of 2 series for now for the reasons I wrote to @aaronmcd earlier. I think it might be the best of both worlds, harvesting earlier in the day and longer in the afternoon, or with a lower sun angle. I can change my configuration in 15min if I have to.
I like that plan & also believe it is important to have the flexibility “series / parallel”. Best to design it “wire size” for worst case scenario “parallel” amperage as that will give you the maximum configuration flexibility. 👍

If you have not purchased a MPPT controller yet, have a look @ Victron & in particular the 100 | 50 Smart.
 

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I like that plan & also believe it is important to have the flexibility “series / parallel”. Best to design it “wire size” for worst case scenario “parallel” amperage as that will give you the maximum configuration flexibility. 👍

If you have not purchased a MPPT controller yet, have a look @ Victron & in particular the 100 | 50 Smart.
I have the Kisae DMT-1250 combined MPPT / DC-DC charger, which is capable of my planned configuration.
 
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How do you hook it up to the battery?
That seems like a good idea. Just there's REALLY not much space left under the bed. Definitely not enough space for a folding chair. I might be able to shuffle stuff around a bit but it's pretty well tetrised in right now.
Just pick another spot on your +/- bus bars to wire up a cheap pwm controller. Off the pwm panel inputs, just put a couple of those fast connect solar cables, maybe 20’ or however long you think you need. Wind them up and tuck them away until you’re ready to hook them up to your panel. You should be able to store the flex panel under your mattress.
 

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Discussion Starter · #30 ·
Just pick another spot on your +/- bus bars to wire up a cheap pwm controller. Off the pwm panel inputs, just put a couple of those fast connect solar cables, maybe 20’ or however long you think you need. Wind them up and tuck them away until you’re ready to hook them up to your panel. You should be able to store the flex panel under your mattress.
Panel under the mattress is a great idea! I don't have a positive bus bar, the 2 studs are getting pretty full. Should be able to cram another lug on there. I don't have my hammer crimper with me, but may be able to find a pre crimped wire or wires.
 

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I run 700 watts on the roof and while parked at Descend on Bend for 4 days, I drained my 200ah Renogy lithium batteries down to 20% most days. We used our microwave for boiling water for dehydrated food, a 400 watt electric space heater at night to keep the van 60 degrees, Dometic fridge, lights, Wrappon toilet, etc...). I was pleasantly surprised to see my battery bank reach 100% at the end of each day so infinite boondocking is possible for me.
 

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Since your solar produces almost 60V at less than 8Amps may I assume you wired your panels in Series? To my previous comment I wonder if series is more advantageous than parallel in the winter since lithiums need Volts more than Amps? Is that correct?

Edit: it probably should say that a MPPT needs a certain amount of Volts before it starts charging?
The "typical" MPPT solar charge controller will not start charging the battery pack until the panel voltage has reached (battery voltage) + (~ 3-5 volts). This varies slightly by brand.

If the battery is at 13 volts, then the voltage at the solar controller input terminal needs to hit (13) + (~ 3 - 5 volts) so at least 16 volts to turn on, some brands need 18 volts under this condition.

At my shop, the nominal 18 volt Vmp panels are often running a "real" Vmp of 15ish volts this time of year (and during fire season), so really barely above the battery voltage. This is true of both the mono and poly panels that I have.

Wiring the panels so that the Vmp is at least 10 volts higher than the typical battery voltage allows an MPPT controller to turn on much earlier in the day - so more effective charging. That is the benefit of what @RV8R is doing.

_

The really bright people who came up with MPPT solar charge controllers did all of the hard work. Their "magic black box" takes in "whatever energy the panels are producing" and outputs "the right energy for battery charging" very efficiently. We can just pay money and enjoy all of their hard work.

____

If your goal is to run nominal 18 volt Vmp panels in parallel into a 12 volt battery bank, then typically you are better off with a PWM controller, like a bogart engineering setup, or perhaps a midnight solar Brat.

At least with the Bogart case, it only requires the incoming voltage to be just slightly higher than the batter voltage to turn on. For that reason, it will start charging very early in the morning with very nominal amounts of light.

It is slightly less efficient on a perfectly clear summer day at that optimum moment in time when the sun is aligned, but much more effective at gathering light and charging when conditions are poor.
 

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That was exactly the point I was trying to make and the reasoning why I wired my 4x 100w in 2 parallel sets of 2 series. That gives me 37.2 Vmp and 10.76 Amps.
 
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That was exactly the point I was trying to make and the reasoning why I wired my 4x 100w in 2 parallel sets of 2 series. That gives me 37.2 Vmp and 10.76 Amps.
If your controller can handle it you would also have the option of 4 in series 74.4 volts @ 5.38 amps 😁

I like having choice & try out different configurations in different “sun conditions”.
 
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