1200 watts of Solar on the roof

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1200 watts of Solar on the roof

August 03, 2013, 01:49:00 pm

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

Re: 1200 watts of Solar on the roof

Reply #1 – August 03, 2013, 02:18:13 pm

How about some pics of the solar system?

Re: 1200 watts of Solar on the roof

Reply #2 – August 03, 2013, 02:30:26 pm

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

Re: 1200 watts of Solar on the roof

Reply #3 – August 03, 2013, 03:50:35 pm

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

Re: 1200 watts of Solar on the roof

Reply #4 – August 03, 2013, 04:21:54 pm

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

Re: 1200 watts of Solar on the roof

Reply #5 – August 03, 2013, 05:09:12 pm

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

Re: 1200 watts of Solar on the roof

Reply #6 – August 03, 2013, 05:12:28 pm

I have 3 8D Lifelines.

best, paul

Re: 1200 watts of Solar on the roof

Reply #7 – August 03, 2013, 05:26:56 pm

Thanks, Do you have any of the wiring and control?

Re: 1200 watts of Solar on the roof

Reply #8 – August 03, 2013, 05:31:02 pm

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

Re: 1200 watts of Solar on the roof

Reply #9 – August 03, 2013, 06:22:23 pm

I updated the earlier posting with that info, here:

1200 watts of Solar on the roof

best, paul

Quote

Thanks, Do you have any of the wiring and control?

1999 U320
2009 Saturn Vue
Miami Fla

--

"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

Re: 1200 watts of Solar on the roof

Reply #10 – August 03, 2013, 06:30:30 pm

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

Re: 1200 watts of Solar on the roof

Reply #11 – August 03, 2013, 07:09:39 pm

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

Re: 1200 watts of Solar on the roof

Reply #12 – August 03, 2013, 08:15:19 pm

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

Re: 1200 watts of Solar on the roof

Reply #13 – August 03, 2013, 09:22:01 pm

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

Re: 1200 watts of Solar on the roof

Reply #14 – August 04, 2013, 12:11:20 am

AM Solar did the work. These are top of the line folks.

We just paid for it.

best, paul

Re: 1200 watts of Solar on the roof

Reply #15 – August 04, 2013, 12:22:54 am

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

Quote

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

Re: 1200 watts of Solar on the roof

Reply #16 – August 06, 2013, 12:00:51 pm

Quote from: Paul Smith – August 03, 2013, 06:30:30 pm

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,

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

Re: 1200 watts of Solar on the roof

Reply #17 – August 06, 2013, 01:27:48 pm

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.

Re: 1200 watts of Solar on the roof

Reply #18 – August 06, 2013, 02:22:27 pm

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.

Re: 1200 watts of Solar on the roof

Reply #19 – August 06, 2013, 08:46:11 pm

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

Re: 1200 watts of Solar on the roof

Reply #20 – August 06, 2013, 11:07:23 pm

Quote from: P. Wyatt Sabourin – August 06, 2013, 01:27:48 pm

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.

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

Re: 1200 watts of Solar on the roof

Reply #21 – August 07, 2013, 02:25:41 pm

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).

Re: 1200 watts of Solar on the roof

Reply #22 – August 07, 2013, 03:25:37 pm

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

Re: 1200 watts of Solar on the roof

Reply #23 – August 07, 2013, 03:36:41 pm

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".

Re: 1200 watts of Solar on the roof

Reply #24 – August 07, 2013, 03:45:20 pm

Quote from: P. Wyatt Sabourin – August 07, 2013, 03:36:41 pm

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

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