36v folding solar panels - scored a bargain

denmonkey · Senior Member

36v folding solar panels - scored a bargain

T1 Terry · Guru

Hi Brett, great video. Have you thought about adding the short circuit current test to go along with the voltage test? I have a lot of semi flexible panels that pass the open circuit voltage test but fail the short circuit current test. Both specs are marked on the back of the panel and it is great method of getting the right angle to the sun for max output as well, the open circuit voltage doesn't change, but the short circuit current does.

T1 Terry

denmonkey · Senior Member

you're probably right, I did set up one set up to the van and the output seemed ok for where they were situated. can't wait for some proper sunny months.

What I need to do, is get myself a current clamp. There's been so many times one of those would have come in handy rather than messing about with inline meters.

I'm going to do some tests and knock up a video on angle and temps to show their impact on output.....eventually.
When I had the panels, now on the van but had them just sitting on the roof without any air gaps under them, the heat in the panel was crazy.
I couldn't even touch them they were so hot.
After I hit them with the hose, the out put came up quite a bit. I'm guessing 10-20% very roughly.
Still, not going to be spraying my panels too often.

thanks for the compliment on the vid and the tip.

Since you have some back ground, have you any input into the lifters on the panels or seen something on your travels that might be useful ?
Trying to formulate a plan at this stage.

cheers Brett

T1 Terry · Guru

Aligning solar panels to the sun on an RV can be a real nightmare. The vibrations make just about any sort of latching eventually let go and the panel array suddenly becomes a sail with not near enough anchoring. You arrive at the free camp and have no idea where the solar array ended up. I have even had stainless bolts with spring washers undo themselves, fortunately on a motorhome you hear the noise of the array flapping up and down, you wouldn't hear that on the roof of a caravan.
To work effectively the array needs to tilt on 2 planes to do the solar tracking from sun up to sun down and correctly angled to the horizon. Hard enough on a ground mounted system but getting the RV lined up facing perfectly east/west so the angle to the horizon only needs to be set up once for the day is close to impossible. That means both angles need to be adjust every 15 mins to get the ultimate sun angle.
Then there is the over cast day or light scattered cloud day, the panels flat mounted produce more than when perfectly angled to the sun.
There are multiple auto adjusting 2 plane solar trackers for sale on evil bay and suit a ground based solar array, but you can't have them opening up while travelling and still expect them to be there when you arrive :lol:
The solar array on my Mazda E3500 pivots from either end, mostly for ease of cleaning under them, but a few times in winter in the Victorian high country I've tilted them and used a leg each side to hold the panels up, first time at roughly a 45* angle. Worked well until the wind came up, too dangerous to try and drop them down again while it was windy so spent the night just waiting for the whole thing to rip off the roof or the glass part to tear out of the frames, never get them above 30* or so now. That does help but not as much as you would think because there is no east/west tracking as well.
Is it worth the effort? on a ground based system, most certainly, more than a 50% increase in the full day harvest during winter, but on an RV, more to be gained by designing a system using small panels like the 60w units and covering the roof where ever a panel can be squeezed in. Shade from a hatch or the air cond will only be on those panels for part of the day when the suns out, but harvest all day when it is cloudy or raining. This type of set up does not suit MPPT control though unless you have multiple controllers and they can be configured in a master/slave set up. Series/parallel into one controller results in every panel in the string where one panel is shaded dropping out if the other parallel string is in full sun.
PWM control works best for these set ups, but it requires all the solar wiring to go to the battery compartment and controlled using multiple solid state relays with one master controller. Simple operating system yet complicated to get your head around initially, but it does work and works well, even when it's raining.

T1 Terry

Whenarewethere · Guru

Never use spring washers.

A nut will work loose because the bolt & hole are not the correct size. When the hole is oversize there is room for micro movement & the nut will work loose whether it has a spring washer or not.

Rather than just making both holes a neat fit, is to tap the second piece of metal so the bolt will basically not move within the hole.

For additional insurance also use a Nyloc nut instead of a normal nut.

Put the effort in & tap holes & get proper tapping fluid.

Metric ISO coarse:

M4 pitch 0.7 hole 3.4mm
M5 pitch 0.8 hole 4.3mm (11/64)
M6 pitch 1.0 hole 5.1mm (13/64)
M8 pitch 1.25 hole 6.9mm
M10 pitch 1.5 hole 8.6mm (11/32)
M12 pitch 1.75 hole 13/32

Use a Taper tap. Then if needed an Intermediate tap, then Bottom tap. But since one is generally bolting two sheets, use a Taper tap.

denmonkey · Senior Member

cheers Terry ,

yes that is my main concern. Not so much being able to work the lifters into the system but how to maintain an appropriate level of structural security when travelling etc.

My panels are sized to provide sufficient power for my needs when laying flat, so it was more of a project thing really to see if I could.
It might be worth my effort to try on the car for ****s and giggles. Would be on a smaller scale and more manageable .

WAWT - I do love me a good nyloc nut. I do have me a couple of tap and die kits at home, dont recall where they came from though but they're not much chop. Only every good for working with soft metal like aluminium. Have pulled them out to try on other staff in the past but they've always got stuck back in the corner as useless. perhaps i need a better set.

T1 Terry · Guru

:lol: Coming from an industry that built big site cranes, nyloc nuts were something used on a back yard project because they are one use items and must be replaced each time or they no longer lock in place. Everything that could be thread tapped was thread tapped and every stainless bolt had a spring washer and flat washer of the same material.
With our installs on thin material we use nut-serts, a bit like a rivet but it has a thread inside. The pivoting points each end of the array that the nut and bolt came loose has since also been fitted with a stainless nut-sert so the hole didn't flog out the way the bolt hole did. Field testing shows up the weaknesses in any set up, so learning from your own vehicle is much better than learning from a customers vehicle :)

T1 Terry

Whenarewethere · Guru

If tapping steel use good quality taps not the rubbish at the standard hardware store. It is critical to drill the right size hole & use a TAPER tap, not an INTERMEDIATE that is normally sold, & with tapping fluid. Turn the tap backwards a bit between every bit of a turn forward. Take is easy so you don't break the tap.

-- Edited by Whenarewethere on Wednesday 17th of July 2019 09:30:09 PM

denmonkey · Senior Member

ooh yes rivnuts. I've not long ago discovered them and have cause to try one out soon to hold on a bash plate to the under side of the pajero where the thread has gone.
I'm going to drill it out and stick on in there. I guess I'll see how well they hold in a touch scenario under the 4wd and getting beaten about.
That should give me some confidence in their staying power.....or not

So is the general consensus, that there isn't anyone angling their roof panels remotely or otherwise ?

cheers Brett.

Jaahn · Guru

denmonkey wrote:
ooh yes rivnuts. I've not long ago discovered them and have cause to try one out soon to hold on a bash plate to the under side of the pajero where the thread has gone.
I'm going to drill it out and stick on in there. I guess I'll see how well they hold in a touch scenario under the 4wd and getting beaten about.
That should give me some confidence in their staying power.....or not

So is the general consensus, that there isn't anyone angling their roof panels remotely or otherwise ?
cheers Brett.

Hi Brett
Do you have a tool to fit them or will you have it 'set' by a place that can set it correctly. No good otherwise for a tough use!
Jaahn

kgarnett · Senior Member

Here are pictures of a couple of quick & easy Isc testers with anderson connector and also an adaptor in case of MC4 connectors.

One version uses a cheap "power meter" and the other uses a clamp on ammeter.

As you know, Voc is only part of the story. I recently tested a panel for which Voc was normal (~ 21V) but couldn't supply any current. I assume a high resistance joint or bad cell(s) somewhere.

Ken

Isc Tester2.jpg

Isc tester.jpg

-- Edited by kgarnett on Thursday 18th of July 2019 02:46:04 PM

-- Edited by kgarnett on Thursday 18th of July 2019 09:48:56 PM

-- Edited by kgarnett on Thursday 18th of July 2019 09:49:37 PM

denmonkey · Senior Member

Ken you're a bloody genius.
I've got plenty of those meters and even more wire and andersons than I can poke a stick at.
Could knock one of those up in a few minutes. Could always just use my multi too but I don't have to make that , so have a zero fun factor.

Jaahn, don't tell me that cry .

I was wondering how they'd go in such situations. I've have a proper tool but am concerned it will eventually loosen and just spin inside the spot where its installed.

cheers Brett

kgarnett · Senior Member

I must have been dreaming when I showed the use of a cheap power meter to measure Isc.

I have certainly used it to measure panel currents into a load etc, and thought that I had also used it to measure Isc. But of course it cant because when measuring Isc the voltage is zero and thus can't power the meter, so no display.

Sorry about that !

Ken

Jaahn · Guru

Hi Brett smile

I have never used nutserts myself so I cannot say much. But I have had problems with some over the years that were not set in place correctly or pulled up tight enough. Just mentioned it really. Seemed to be incorrect fitting that was the problem. A bash plate might be a test for it ! confuse

Jaahn

denmonkey · Senior Member

kgarnett wrote:
I must have been dreaming when I showed the use of a cheap power meter to measure Isc.
I have certainly used it to measure panel currents into a load etc, and thought that I had also used it to measure Isc. But of course it cant because when measuring Isc the voltage is zero and thus can't power the meter, so no display.
Sorry about that !
Ken

aww Ken, you have me so excited about my next free sunny day. Guess there is only one way to find out.

Multi meter it is. Was fun while it lasted. ... hang on, don't these meters also have an additional input on the side for them to remain on when the 'source' isn't active ?

I think there is a little 3-4 pin connector on one end but I can't recall if it's for a power input or whether it was for multil cell batteries like for Remote control batteries .

Will have to suss it out.

Thanks Jaahn for the clarification. I'm pretty committed to trying it out. If it doesn't work, I'll have to pull it and tap the existing hole but that means buying a kit to do so and a proper one wont be cheap for that size and my mate already has the bits for the riv set up. so it's free to try biggrin

I shall document my success or failure.

actually whilst we're talking rivnuts, the mate who is lending it to me stuck 2 in the end of his awning, then placed a small eye bolt in both ends to attach guy ropes to.

Basic but works very well and seems strong enough. saves tying the ropes around the arms etc and gives something to tie on to.

not sure if that makes sense.

cheers Brett

kgarnett · Senior Member

Brett,

You're right, there is a 3pin connector socket on the source end of the Power Meter for an external power supply to enable the meter to operate down to zero source volts.

The following text is copied from the "Watts Up" pwer meter manual but I imagine it similarly applies to the cheap copies.

Must try it !

Ken

6.5 Using Auxiliary Power

By connecting a DC power source (power supply, receiver battery pack, battery, etc.) of at

least 4.0 V to the 3-pin connector on the SOURCE side, the "Watt's Up" can measure down

to 0 V. This makes it possible to measure the characteristics of a single battery cell.

The 3-pin connectors socket will accept a Futaba J type, JR or HiTec type servo plug

connector. A suitable auxiliary power connector with wires attached is available for

purchase from our website.

Pin 1 is Negative (0 Volts), pin 2 (middle pin) is Positive. Pin 1 is the pin farthest from the

"Watt's Up" SOURCE wires. Pin 3, on meter versions 2.1 and above, is for reset of

accumulated readings. See below for description of reset operation.

When using Auxiliary power, you may see small measurement values when the SOURCE

and LOAD leads have nothing connected or are shorted together. It is neither unusual nor a

problem for there to be small values displayed in this situation. This will not affect

performance when making real measurements.

Aus-Kiwi · Guru

I just use plenty of sicoflex . .

kgarnett · Senior Member

Brett,

OK, I tried powering the "Power Meter" from an external source and can now measure Isc current - All good ! biggrin

Ken

Jaahn · Guru

kgarnett wrote:
Brett,
OK, I tried powering the "Power Meter" from an external source and can now measure Isc current - All good !
Ken

Hi Ken smile

Thanks for that info might be useful as I have a couple of those meters. Gees it is good to spread the knowledge about. biggrin

The problem with having a couple of meters is you get a couple of different readings too aww but I am not being paid to be precise now so I can wing it a bit confuse I have several multi meters too with the same problem.

Jaahn

denmonkey · Senior Member

hazaa to all involved. thanks for being the test bunny Ken.

You're right Jaahn, the only answer is to sell or give away all of your test gear, bar one unit, to someone who will very much enjoy them.
hmm, I'm not sure where you would find someone like that who would be so willing to help you out of that bind wink

Ken, If I can swing this with Jaahn, you wanna go halves in his stuff ?

cheers Brett

kgarnett · Senior Member

Yes, of course I'd be willing to help out Jaahn move his stuff.

It would just add to all my stuff which my wife classifies as junk. but of course in reality her stuff is junk and mine is all "good stuff"

She just doesn't understand.

Ken

-- Edited by kgarnett on Friday 19th of July 2019 05:33:01 PM

T1 Terry · Guru

denmonkey wrote:
ooh yes rivnuts. I've not long ago discovered them and have cause to try one out soon to hold on a bash plate to the under side of the pajero where the thread has gone.
I'm going to drill it out and stick on in there. I guess I'll see how well they hold in a touch scenario under the 4wd and getting beaten about.
That should give me some confidence in their staying power.....or not

So is the general consensus, that there isn't anyone angling their roof panels remotely or otherwise ?

cheers Brett.

You can buy both steel and stainless steel rivnuts, maybe be even high tensile from a specialty supplier, but no idea how you would pull it :lol: If you have a rivnut that isn't holding properly, cut the bolt head off and drill it out, or if you manage to get the bolt out, use a bolt long enough to go all the way through the rivnut and enough for a nut and a couple of flat washers on the bolt shank as well. Screw the bolt through till there would be some thread sticking out the other end, then hold the bolt head and tighten the nut onto the 2 washers as tight as you think you can go without either stripping out the thread of an aluminium rivnut, or snapping the bolt in a steel rivnut. This will retighten the rivnut. If you use this method for high load bearing rivnuts then every time you tighten the nut up the bolt the rivnut is tightened and the bolt takes the load through all the threads of the rivnut. Never a problem with spinning rivnuts then.

T1 Terry

Peter_n_Margaret · Guru

The OKA has dozens of riv nuts in it from new. I am not much of a fan, but agree they do a job that is sometimes hard to do some other way. I have had many failures of the originals, sometimes due to corrosion and sometimes due to them spinning in the original panel.
I replace them with either steel or aluminium ones. It is useful to add a couple of tiny grooves in the panel with a small triangular file to give them some extra grip.
I have also used some big ones (M12). They can be pulled up by tack welding to the panel then pulling up with a bolt, washer and socket on a breaker bar. They rarely fail.

I often use m6 aluminium riv nuts in a piece of aluminium that is then glued to the skin of sandwich panel with Sikaflex 11FC to provide a high load attachment point to a relatively fragile skin.

Cheers,

Peter

denmonkey · Senior Member

thanks boys, i do like the idea of chucking a weld on on it. I have a welder and am sure I could tack it but thats about as good as it would get.
I don't believe I should be trying to arc weld on vehicle. bad things happen dont they.

I've got a mix of the alu and steel nuts. Guess, I'll just suck it and see. keen to try them out for the first thime.

The reason I'm going with this, is where the bolt goes through the bash plate to hold it on, is into a square tube cross member of sorts.
so there's no getting behind it to do the usual stuff. :(

cheers