How many solar panels do I need?

Rickf1985 · October 27, 2015, 06:41 PM

. What I am trying to figure out is how many of these I would need to use to build a decent system and do I need a charge controller. You can see the specs on the data tag. These where hooked to flashing STOP signs and had 22 Ah 12 volt NiCad batteries in them.

DRMousseau · October 27, 2015, 08:49 PM

Nice!!! I've always thought of a good solar charging system,... and even more so with the 34' Cruise Air.

What these lack in output (which isn't all that bad), is certainly made up for in durable quality! These things gotta be tough to survive the roadside throughout the year. I've heard they can take a 1" stone from a passing gravel truck!

I see a lot of 2'x4' panels of about 80-100 watts available for RV use. Your certainly gonna need a charge controller to maintain proper charge voltages. I think the general rule is 2w for every 50ah of deep-cycle battery capacity, even individually by themselves, being 20w output, a controller will be necessary for jus maintaining charge on your much bigger deep cycle wet-cell battery. They probably had none for maintaining their ni-cads. But ya gotta limit your charge rate of deep-cycles to about 14.5v max.

I've been thinkin a 400w system with an MPPT controller (more efficient). This won't even come close to handling the AC,... but it should be fine for my otherwise excessive power use, 3000w inverter, convection/microwave, 120v refrigerator/freezer, 2-DC propane furnaces, 2-DC ceiling fans, DC lights and misc. electronics. I figure I can easily use about 2kw a day with all that,... and 400w system SHOULD, keep me happy and offline.

So,... how many do you think YOU might need?

ClydesdaleKevin · October 28, 2015, 10:05 AM

First, yes you will need a charge controller...and I highly recommend Morningstar, especially their MPPT line of charge controllers.

Secondly, at just 20 watts a panel, I would say you will need as many as you can fit on your roof, on your AC shrouds, anywhere you can fit them...lol!

We have 705 watts of solar on the roof of our RV (comes out to more like 730 in real life application, but they are rated to 705). We have them flat mounted, and they are barely adequate for boondocking in the winter based on our power usage...which is minimal. I still end up running the genny every few days to top off the battery bank fully (6x6 volt Interstate golf cart batteries). I will be building a tilt system for them shortly, which should help tremendously.

So the short answer is as many as you can fit, and as many as you can afford, with the best charge controller you can afford.

Kev

gadgetman · October 28, 2015, 01:51 PM

I agree with Kevin, put as many as you can. For me I like to have double my battery bank AH in wattage. I have a 400 ah battery bank and 800 watts of solar. This still charges on cloudy days, At a min you need to match your battery bank AH in watts for solar panels but that will barley reach a full charge in one day and it wont of cloudy. With double your AH in watts it works really well.

If you can only put a few panels and 17.6 or so volt panels wont add up enough use larger voltage panels and a MPPT controller.

My system will give me 40 amps in full sun if my batteries need it.

Solar rocks !!!! I run a 1500 watt inverter and can run everything except the roof AC.

Its all about watt usage management in the dark

Rickf1985 · October 28, 2015, 05:53 PM

Thanks guys, Obviously my 6 panels at 120 watts total is not going to do much for me. Advantage being is that they were free. I may build a setup that I can deploy outside of the RV while camping and not mounted to it. I really do not want to put any holes in the roof. I still have not found the source of a persistent leak yet other than somewhere on the roof. I have been camping for many years in nothing bigger than a slide in for a pickup and I am very stingy when it comes to power usage. I can go three days on a single battery without running it below 50%. About the biggest power user in the RV is the water pump and since I watch water like I watch power it lasts a long time.

Oz · October 29, 2015, 09:07 PM

I hope you'll let us know what you finally decide on to meet your needs. I don't know diddly about all that electrical stuff, but those who do might greatly benefit from the breakdown on the load requirements and what the component specs are you choose to meet them!

DRMousseau · October 30, 2015, 12:02 AM

Wow! There it is Rick!!!
A GREAT project for your approaching retirement!!! Lol! (gotta enjoy retirement,... in every way you can!)

I like Kevin's setup,.... and with the room up on top and the added GVWR I now have, I can't help but to consider solar jus a bit more now. There's nearly 400lbs of battery there! I've always thought a tilt system was near essential, partly to keep accumulated debris clean from under the panels, and mostly for efficiency. But I jus haven't yet seen a good sturdy and somewhat universal tilt system that doesn't limit your parking position so much and wouldn't make me nervous on the highway!

And I kinda like shady locations too. NOT so good for solar needs though. I've also wondered if the panels would provide a bit cooler rooftop in those hot sunny locations I typically avoid. Not sure it would be significant, but maybe.

Kevin- I notice some nearby vent covers and such that would cast shadow on some cells occasionally,.... have you seen any significant effect from that??? And do you use any kind of "real time" battery monitoring technology to monitor usage, charge rates, remaining capacity and such???

Here in North Michigan, I don't think we've had more than two solar hours in the last WEEK!!! And it jus gets worse for the next two months! I sometimes think about wind, as it's been rather breezy lately and it blows thru the trees all winter here!

Right now,... I'll slowly add battery and charging capacity as the budget allows, and consider all this a lot more.

Rickf1985 · October 30, 2015, 07:07 AM

I will just be making up a supplementary charging system with what I have. I do not have the money to buy anything else to add to it. As I said, these were free so the price was right. If I am going to spend money it will be on a decent monitoring system. I think Dave has put up some info on them on here somewhere. Maybe in retirement I will learn how to search successfully for stuff? Yea, right! Some old dogs just can't learn that trick. N:(

DRMousseau · October 30, 2015, 12:55 PM

With a minimal cost charge controller (about $30-$40 or so), these panels individually would make a GREAT maintenance trickle-charger, for long-term storage of RV's, autos, or anything with an installed 12V battery system.

Environmental changes of temperature, humidity, and the various small voltage losses incurred during storage (like radio memory, clocks, etc.), can leave one with an unexpected weak or even dead battery that can risk costly damage. An unused fully charged battery sitting on a shelf can lose 10% of it's charge each month. At 40% charge (yet still reading good voltage) a battery can begin to freeze if temps drop below 20 degrees.

Of course you'll only have some charging on those crisp CLEAR freezing days, and you'd still better be checkin' your batteries on a regular basis.

ClydesdaleKevin · October 31, 2015, 08:07 PM

Quote from: DRMousseau link=topic=11835.msg68591#msg68591 daquote author=DRMousseau link=topic=11835.msg68591#msg68591 date=1446177777]

Kevin- I notice some nearby vent covers and such that would cast shadow on some cells occasionally,.... have you seen any significant effect from that??? And do you use any kind of "real time" battery monitoring technology to monitor usage, charge rates, remaining capacity and such???

As long as I park with the starboard side of the rig (right/passenger side) facing the South, I get no shadows on the panels...I figured shadows into their location on the roof, and the easiest way to do it was to make sure I park it that way. Which will make tilts a lot simpler...they only have to be hinged on the starboard side.

As far as real time battery monitoring, I keep it simple. Aside from the Morningstar remote panel which tells me amps in and out, etc...I mostly rely on an inexpensive digital volt meter gauge I installed near the remote monitor which I can view at a glance from my desk in the RV to see remaining battery voltage.

Kev

ClydesdaleKevin · October 31, 2015, 08:12 PM

Quote from: Rickf1985 on October 28, 2015, 05:53 PM
Thanks guys, Obviously my 6 panels at 120 watts total is not going to do much for me. Advantage being is that they were free. I may build a setup that I can deploy outside of the RV while camping and not mounted to it. I really do not want to put any holes in the roof.

120 watts is more than most people have for RVing, and if you deploy it correctly (remotely and each panel tilted to the sun at an ideal angle), and with a good charge controller that can take full advantage of the 120 watts, it will drastically cut down on your generator usage, and I think you would be pleasantly surprised by the results.

Kev

M & J · October 31, 2015, 09:55 PM

Pretty sure starboard would be the RIGHT/passenger side of the craft Kevin... Hm? W%

joanfenn · October 31, 2015, 10:18 PM

Maybe Kevin has had too much port. Left side= port side, right side = starboard side. Mike was right.

1990HR · October 31, 2015, 10:25 PM

When I was younger taking Sailing lessons the way I remembered it was "Port" Has 4 letters and "Left" has 4 letters.
Also the right and left of any vehicle is when you are in control of it IE driving or riding it (Motorcycle).

DaveVA78Chieftain · October 31, 2015, 10:39 PM

And he calls himself a sailor (silent service)

joanfenn · October 31, 2015, 11:10 PM

You have to be able to count to four also. :)rotflmao

DRMousseau · November 01, 2015, 01:18 AM

I suppose that ability to make a four count, is why the Cruise Air is only equipped with a 3-point battery condition indicator of Good, Fair, and Low.

Prior to installing a Tri-Metric Monitor, I relied mostly on a multi-meter and regular hydrometer readings. The monitor is centrally located "in the fo'c's'le, inboard, and jus aft of the bow" (LoL!), between the front seats, on a panel that has replaced the original television.

Rick,... the Tri-Metric Monitor is jus plain WONDERFUL, and I can't blame ya for makin' something like this your next priority. I activate one of the alarms when I'm boon-dockin' to give an audible and flashing alert at a point when I MUST fire-up the genny. Nice when your not payin' close attention to your power usage on a busy day.

Kevin,... Maybe I watch too many NASCAR races, because I'd be very nervous if anything on the roof was hinged anywhere but on the forward side and it still better be dang secure! But that's jus me,... and my uneasy feelin's about such.

I think these panels would make GREAT little outdoor "charge stations" in public parks, bus stops, beaches and such, where one could plug in their phone or tablet for a quick charge when needed. If electric assisted bicycles ever became popularly accepted, I could imagine these at public bike racks too.

But if you did "deploy" these out at camp, and adjusted as needed on a bright summer day, I think you might only see about 10-20Ah of your battery usage restored daily at the very VERY best,... and that might be enough in the summer, for miserly retired ol' man! LoL!

ClydesdaleKevin · November 01, 2015, 07:58 AM

A typo. Of course starboard is on the right side...which is why I also said passenger side...lol!

Kev

Rickf1985 · November 01, 2015, 09:55 AM

Quote from: joanfenn on October 31, 2015, 10:18 PM
Maybe Kevin has had too much port. Left side= port side, right side = starboard side. Mike was right.

Kevin made a mistake and I MISSED it?!!! D:oH!

ClydesdaleKevin · November 01, 2015, 07:21 PM

LOL!!! Yes...even the great Kevin makes mistakes...but I did say passenger side...which means I meant the right side.

It wasn't Port...it was Arrogant b-stardo Ale (Automatically edited by Marks funny cuss word filter...lmao!!!). Yummy stuff!

If you make yourself a remote array stand for that 120 watts that you can aim at the sun, you'll actually get quite a bit of benefit out of it.

Kev

Rickf1985 · November 01, 2015, 08:16 PM

Well, today my right hip went out on me and I cannot put any weight on it so I am thinking my plans are on hold for the time being. I'll be calling the Doctor tomorrow.

M & J · November 01, 2015, 09:23 PM

Sorry to hear that Rick. Some kinda first day of retirement brother.

Oz · November 01, 2015, 09:43 PM

Hope it's not serious, Rick. Take it easy on yourself.

TerryH · November 01, 2015, 11:00 PM

Best of luck with your hip. Hope you realize that my various "Retirement" comments were wishing you enjoy your new and different lifestyle.

Rickf1985 · November 02, 2015, 07:58 AM

Well I am able to walk today but it still feels weak so I guess that is a good sign. Still need to make an appointment but you know how that is, at least three to four weeks to get in.