Well, we bit the bullet and had AM Solar put 8 150 watt solar panels upstairs. Four instances of two panels in series. The controller might have worked with two instances of four panels in series, but Greg pointed out that would reduce redundancy. All panels secured with tape.
What a great team, especially Greg and Deb.
So far this summer we're replaced a kitchen faucet, toilet and refrigerator, and added solar panels (in order of increasing cost ;o)
Ya think we'll be criticized for spending Nac bucks out of town?
best, paul
How about some pics of the solar system?
yes I second the pictures. You have a great system there and will be off the grid I am sure. We have 700 and can live totally without gen and hook up as long as sun shines, so you are way ahead, as long as your storage bank (batteries) are good and lots of capacity.What do you have for batteries-I forget?
Since I changed over my battery wiring (to a common Bussbar) I feel there is less charging going on and better efficiency with them. Will take a lot longer to prove but think this is correct.
John H
Yes, pics!
One huge advantage of the MPPT charge controllers is the ability to gain high voltage into the controller while still charging a 12vdc system. Because battery charging is always a matter of voltage differences, as the sun goes down having 24v, 36v, 48v or higher voltage to the controller means that the panel voltage takes a lot longer to fall below 14vdc (which is a reasonable voltage to charge 12vdc batteries.
The smaller wire size helps a lot for installation, too.
But I do agree that redundancy is good.
There is no way I could accommodate 1200 watts of solar power in my rig because I don't have enough places to install sufficient batteries to soak all this energy up! I suppose I could just make all three batteries "house and start" batteries. That would help.
Craig
Anticipating this question I climbed up and took some pictures. Fortunately, SWMBO was not around. But the pictures I got were not very good.
Now That I've found a cord that talks to me phone AND my computer perhaps I can upload the picture I have.
Unfortunately, I did not take a pic at AM Solar. THAT would have shown it nicely.
more, later
best, paul
Here are the photos I have. The first photo - 4797 - shows 2 panels at the rear of the FT. That's 2.
The second photo - 4798 - shows 3 panels ahead of the rear AC. That's 5.
You third photo - 4799 - shows a panel to the left of the rear AC. That's 6.
The fourth photo - 4800 - shows two panels to the left of the Datastorm unit and ahead of a vent. That's 8.
Once the Datastorm is out there might be room for two panels to the right of it!
best, paul
PS> I added photos of wiring and control
4801 is the monitor in temp location on front of fridge
4802 shows wiring going thru the floor behind the fridge
4803 shows the controller and switch
4804 shows the battery compartment and breaker
I have 3 8D Lifelines.
best, paul
Thanks, Do you have any of the wiring and control?
Paul I have 3 as well so yours will be charged faster than mine. What size wire did they run down the fridge back. Hope it was at least #4. I have both 4 and 2 (from controller) going to battery bank.
John
I updated the earlier posting with that info, here:
1200 watts of Solar on the roof (http://www.foreforums.com/index.php?topic=18787.msg130191#msg130191)
best, paul
--
"When you arise in the morning, think of
what a precious privilege it is to be alive...
to breathe, to think, to enjoy, to love."
~ Marcus Aurelius
The controller could not accept #2.
So they used a short (1.5 in or so long) connector between the controller and the #2 wiring.
Not sure about the other wiring sizes.
If I had it to do again I might use 2 AM Solar controllers for redundancy.
best, paul
Paul,
Looks great. I am just about to start installing ours if the heat holds off a little longer. You did a nice, neat job. Hope ours looks half as good.
Pierce
You should be able to light up Detroit with that setup. The photos give a good idea of the installation. Thanks! :)
I have two 240-watt (24vdc) panels ready to go up. I have 3M tape but I'm not sure it's the same stuff everyone else is using. Do you happen to know which tape they used?
I also have two flexible panels that I have been planning to install along the radius of the roof edges. They are 12vdc and the plan has been to glue them down (they actually have their own glue) and then run those two in series and the other two in parallel for a total of 520 watts.
Pierce's discovery of an MPPT controller that can handle much higher voltage than is commonly available has made me rethink all of that, however.
Two controllers are completely feasible, however. But with 12-volt panels you could just connect them directly to the batteries and watch the voltage with a digital volt meter if the controller went out. That would be annoying but would work until you got a replacement controller.
My move to 24vdc panels precludes that option.
Craig
Pauls panel z brackets are held on like mine with 3m vhp tape and then caulked around with the Ditech?? caulk. Mine have been on 3 yrs now and no movemnt whatso ever even in the heat. AMSOLAR have been using the tape for many years and Greg told me never heard of any moving. I think they even started using the body moulding tape that car places use-again 3m. They are a first class place and do not do things half co---d!
Greg (owner) for a time was thinking of growing herbs in his basement slides with the power he had on his Winnabego 40ft. Deb said she was not too happy with that.
Paul, have you got the room in the centre bay under the compressor like I have for 2 more Lifelines? that would make for a real power house!!
john H
AM Solar did the work. These are top of the line folks.
We just paid for it.
best, paul
If the bay you're referring to is just behind the batteries, there is room for 2 Lifelines, John.
But not in the center. That's where the Aqua Hot is. And that bay is warm when the AH is running.
But you've got me thinkin'
best, paul
Paul,
Yes, using two AM controllers would cut your chances for total failure down and keep half of the array online but at the same time, increase the probability that one could fail. Why not just buy a second MidNite 150 for $600 and keep it for a spare? The 60 amp controllers that AM has listed on their site are $540 each and your system would need two. For $60 more, a spare Classic 150 would handle the entire array if the primary controller had a problem.
Pierce
wa_desert_rat:
You indicated that you have 24vdc and 12vdc panels, which must be what is referred to as "nominal voltage".
To be sure that your panels are compatible and can be used together to supply full wattage, you need to compare the "Volts Open Circuit" or VOC and the mppt voltages. The VOC on a NOMINAL 12vdc panel can vary from circa 18 volts to 22 volts. The mppt voltage of an 18VOC panel will be circa 14.5 volts while a 22VOC panel will have mppt voltage of circa 17.5 volts. Before I buy a panel, I check the VOC (digital volmeter in bright sun light) and the "short circuit amps" SCA (also with a digital meter in bright sunlight). If the working voltage of the panels you mix are not compatible, you will not get as many watts as you expect, and get very little from the lower voltage panels.
If you add more batteries to your house battery bank, the relative location of those batteries is critically important, or more specifically, the length and size of wires connecting batteries together, connecting batteries to charging sources (alternator, charger, solar), and connecting batteries to loads. Long or small wires will limit current flow, resulting in one battery working much harder than others, or a battery which is chronically over charged, or a battery chronically under charged.
The ideal situation would be all batteries in the same bay, with 0000 battery cables of exactly the same length between batteries (+ & -) with the main "plus" connecting cable at one end of the battery bank and the main "minus" connecting cable at the other end of the battery bank. The intent here is to have the same length and size of wires on each battery.
Foretravel installed the three start batteries in my 96 U320 behind the passenger rear tires, with the three house batteries just behind the driver side front tire. Two, thirty foot long 000 cables connected the house batteries to the starter (one negative, one positive). This sixty feet of cable became the current limiter when starting the engine with the boost switch on. The amount of boost current from the house batteries was almost the same with one house battery as with three. With dead start batteries, my house batteries could not start the engine. Moving the house batteries to the start battery bay provided faster cranking than with the start batteries.
Wyatt, open question here- if I were to add a couple more batteries to the 3 I have for coach is it still important to have the cables the same length (as they all are now) on these extra ones even though mine are connected to a common BUSSBAR for both + and -. Mine are not connected together any more so I was wondering if the same principle applies?
John H
Wyatt... if I use a separate MPPT controller for the two 12vdc (nominal) wired in series (they are only 70-watts each) then that should eliminate any sort of compatibility problem.
I suppose that there might be some circumstances in which someone could measure panels before buying them... but that would not be an easy situation to arrange with even the most open outlet.
At this particular time I'll have one - slightly smaller - MPPT controller and the two 12vdc panels are of a type which allow better charging in conditions which would render other types of panels useless. So I'll have an opportunity to test the system out under various scenarios and determine which way works best.
Craig
John:
The short answer is "yes". It is important to have the cables of the same "capacity". A common bus bar for both "+" and "-" is what I am doing, with equal capacity cables between the "bus bar" and each battery (and each load).
THE LONG ANSWER:
Capacity or length - what is the difference. The amp capacity for a cable becomes smaller as the length increases and smaller as the diameter (really area) decreases. Think of a garden hose and the number of gallons per minute out the end. With a larger diameter hose, more gallons per minute. With a shorter hose, more gallons per minute.
Ampapacity & voltage drop: As the ampacity (amp capacity) of a cable decreases, the voltage drop per amp increases. As the amps increase, so does the voltage drop. Low voltage at the starter during cranking means more amps and more heat which results in a shorter life. The starter must develop enough torque to turn the engine, the higher the voltage at the starter, the faster the engine turns, the lower the amps and the cooler the starter.
I am taking the concept of having each battery work as hard as any other battery to the extreme. I have amphour meters on each battery (I have three) and I am checking every boondock day that each battery reaches full charge at the same time of the day and that each battery provides the same amps during starting (no start battery bank) or when using the inverter. I am close but not quite there yet.
I have six foot long "0" cables on each 8D battery behind the rear tires. Each of these "0" cables goes to an amphour shunt under the foot of the bed. The other end of each amphour shunt connects with a heavy, short copper conductor to the "-" common brass bolt (like a bus bar). Also connected to the "-" brass bolt is the "000" cable from the starter, an "000" cable connected to the frame, and all the other "-" wires. The "000" negative from the 8D battery just behind the driver is connected to the "-" lug on the starter but could be connected to the "-" brass bolt for load balancing.
Under the foot of the bed is also a "+" brass bolt and cables from all batteries. Also under the foot of the bed are the "solar controller", the inverter, the converter, the isolator diode block (not used now), and the A/C relays.
By the way I moved the sense wire from the alternator to the "+" brass bolt under the bed with a resistor so that I can increase the charge voltage to 14.3 volts at the batteries (14.2v regulator).
As you may remember I have done the Bussbar install using 2 pcs of 2" x 3/8 copper bar and drilled and threaded each connection for the cables. My batteries (3x 8D Lifelines) are only 18" away from bars so I have equal lengths of 4/0 welding cable as my connections. My solar charge feed from controller/breaker panel is #2 copper to + bar. Seems to all work fine !!
If I did add 2 more batteries they would have to be about (cables) a foot longer??
John
wa_desert_rat:
Before I can answer your question, I need more information. I need VOC and SCA for each panel and info on your controllers, as well as how you want to connect your panels and controllers.
Generally, having more than one charger on a battery bank will not result in getting the full capacity from each charger and may result in zero from one charger. Even using two identical solar controllers may not provide maximum charging because their set points may not be the same. Using different solar controllers would not likely provide the maximum from each solar panel and could cause on to "smoke". Some controllers short the PV+ to the PV- with battery at full charge, some open circuit PV+ and PV- at full charge. Some controllers open circuit PV+ & PV- to check the VOC every few seconds. All controllers monitor the battery voltage, while some also monitor charge amps (into the batteries using an amphour shunt or out of the charger) and some allow for battery capacity, and or battery type and battery temperature adjustments. Any increases in battery voltage or amperage caused by one controller will affect the amount of amperage from the other controller.
One 70 watt panel could be safely connected directly to your start battery bank without a controller to advantage. Probably even two 70 watt panels also, just check battery voltage at sunset to be sure your batteries are not being overcharged.
I use both solar and converter charging when connected to shore power, only if there is insufficient solar to keep the batteries charged, and then generally turn the converter on at sunset and off at sunrise.
I am curious, can you provide details about this statement:
"two 12vdc panels are of a type which allow better charging in conditions which would render other types of panels useless".
My 70 watt panels are flexible type (unisolar) which are supposed to be less impacted by shadows on small areas of the array. Shadows reduce (or stop) charging by those members of the array but do not completely shut the entire array down as do most of the solar panels sold.
Craig
Re: Using two charge controllers on the same battery bank: here is a forum with a discussion about this very topic.
Can you use two separate MPPT charge-controllers? (http://www.wind-sun.com/ForumVB/showthread.php?17068-Can-you-use-two-separate-MPPT-charge-controllers)
Craig
FAQ about uni-solar flexible panels. Since these will be mounted flat with no way of raising them, I wanted to have at least some ability to charge in dicey conditions. Hence I ordered two of these (for something like $89 last summer). I have not put them into service yet as there are some items we need to get off the roof (old roof-top carrier and an old satellite dish) to make room. Other things have gotten priority until lately.
Q) Does the panel perform as well when it has shadows on it?
A) All UNI-SOLAR flexible modules (>10 watts) are equipped with bypass diodes wired across each solar cell. The bypass diodes provide an alternate pathway for electricity that might otherwise flow into a shaded cell. If 10% is covered by shadow, you will only lose 10% of the module's maximum power output. This is a great advantage of the UNI-SOLAR product line. Most competitor products have bypass diodes in the junction box where a 50-100% loss of power may occur when only 10% of the module is shaded.
From: Uni-Solar Flexible FAQ (http://www.unisolar.com.au/FAQflex.html#8)
Craig
wa_desert_rat
I was not aware the there are solar controllers that can cooperate via cross talk, except for the very expensive Outback line. One article you mentioned indicates making one controller be primary and the other be a follower. I am curious how that is done.
I studied the uni-solar panel advantages a few years ago and concluded the their advantages came at a price. They have become much more competitive in the last few years.
Partial Shading Power lose:
I agree that Uni-solar panels continue to be more resistant than other panels to partial shading. I carefully placed my panels on the roof such that partial shading from vent covers or A/C units will not occur as long as my coach is pointed east. Also my panels are not flat on the roof and provide maximum power when my coach is pointed east. I seldom park in the shade.
Another advantage of Uni-solar which you did not mention is their ability to maintain 100% output with the sun rays at up to 15 degrees off the perfect 90 degree. Unisolar has a clear weather protection with an organized dippled surface which refracts the light. I saw an article on this where two competing panels were attached flat on the roof of a motorhome and indeed, the Uni-solar provided more amphours as the sun moved through the sky.
Uni-solar clear weather protection is also very tough and will tolerate large hail stones which will crack other panels.
I think that it is a bummer that the company with an innovative products such as the Uni-Solar flexible solar panels couldn't survive in business in spite of their fantastic product. I guess they were just ahead of their time... their panels turn up a lot on eBay these days for pennies on the dollar compared to what they sold for when the company was still in business. You can find them in various stages of completion from fully completed with the self stick adhesive and the pigtailed connectors attached to just the individual cell segments. I invested in 408W worth of the finished panels for about $650 or so. I got two of the 136W panels which are almost 18 feet long by 15 inches wide and two of the 68W panels which are slightly less than 9 feet long by the same width. There is only room for two of the longer ones on our 36 coach, but I believe I could add another six of the 68W panels if I wanted to max out the available roof space for a total of 816W. The 68W panels are 12V while larger ones are 24V (nominal). The current plan is to get the midnight solar classic 150 controller and wire the 12V panels in series (in effect making them equal to one of the larger panels) and the 24V panels in parallel but until I get the controller and do a bit more research I'm not sure on that. The idea here would be to have three banks of a hundred and 136W each at 24V. I could however just put them all in series for a total of 72 V and let the midnight solar controller dole it out to the batteries as it sees fit. If and when I get the other panels, I will have to make a decision there because it will be close to the maximum capacity of the controller if I put them all in series. I know this is oversimplifying a more complex calculation, but that's just where my thinking is at the moment, subject to new information of course....
I'd certainly be interested in any comments about that scheme! Since you can walk on these panels, I'm not too concerned about restricting access to components on the roof. Although note I said walkable, not danceable ;D if I was actually working on the roof say to replace the air conditioner, I would cover them with something like an exercise mat and a piece of plywood to protect them.
Don
Don... my original interest in the Uni-Solar products was to place along the roof edge outboard of the refrigerator vent on one side and the external TV antenna on the other. This space, otherwise unusable, would give us some charging on sunny days depending upon the orientation of the coach. I have no idea if the glue they are provided with will keep them down at 60mph but I propose to find out.
Pierce's revelations on that high voltage MPPT controller make me think that series is the way to go as long as you can keep within the maximums for both voltage and current. I had not realized that they were even better than I had thought until Wyatt mentioned the 15-deg off 90 sun alignment advantages. Maybe I should have gotten enough to cover the coach.
Wyatt's comments about matching panels are interesting. I would have thought that putting all panels in series would make any panel differences a non-issue. Simply add up the voltages and, Viola! (grin) you have charging.
I did not do the cover-the-roof thing because I wanted to be able to raise some panels for better charging. So the Uni-Solars would give an advantage when we were not parked perfectly or not long enough to warrant raising the 24v panels. We'd get at least some charging.
But as I get beyond the 70-year stage I find myself less eager to get up onto the roof for anything. Luckily, my wife is 13 years my junior and still nimble enough to go up without stress. So I'm wondering, like you, whether simply covering the roof with the Uni-Solar panels might not be the best way to go.
Craig
There is an aftermarket company in Arizona that takes the Uni-Solar panels and apparently makes their own custom trim pieces and charges a premium price for the panels and installation. I plan on screwing a piece of trim on the leading edge at least and sealing around the edges with caulking or perhaps Eternabond tape. As far as I can tell, not having actually installed panels as yet, the adhesive backing seems to be very eager to stick to anything it comes into contact with... it says in the instructions that you only get one shot to stick it on where you want to go. If 3M VHB tape can hold on large solar panels with only the surface area of the bracket footprint, I don't think these panels will have a problem staying put! I do like the fact that it retains a cleaner look than panels mounted on brackets. I did some testing in the sun with a temperature probe, and the rise in temperature behind the panels seemed to be a few degrees at most... Not really significant. Perhaps the temperature will rise more when they are actually dispensing current to the controller, but that remains to be seen.
Don