diy solar

diy solar

how would one test different configurations of panels to find which gives best results?

J

Joe_

New Member
Joined
Sep 21, 2022
Messages
105
What would you need to do actual comparison testing of the output of some solar panels mounted in different angles and configurations?
Before I commit to permanently mounting my panels in any one configuration I would like to be able to measure the difference in output over the course of a day of a panel, or a few panels to see how different orientations affect the actual output. Is there a tester that does this that is affordable? I really don't know.

I have several used 235 watt sharp panels and a BMV-712 smart battery monitor new in the box. I don't have the 48 volt batteries yet, the only charge controller I presently own is an EG4 that requires at least 120 volts PV to operate.

I'm looking to keep this as simple as possible but also accurate.. I also have some lead acid car and truck batteries in good shape and various capacities. Any ideas on how to do this?
 
Pvwatts will give you a decent estimate.

Because solar varied day by day, your best test is to have panel level monitoring and put them all out on the same day, at different orientations. You want a day with stable weather so morning clouds vs afternoon sunshine doesn't bias the results.
 
Is a panel level monitor something you purchase or is it something that you put together yourself?
 
Last edited:
TBH if you have a clear installation with no shading I don’t really buy that measuring beats PVwatts except to learn more deeply. Once that knowledge is acquired a solar pro or seasoned diyer would just use PVwatts or similar tool

Also with unshaded module level mainly helps to identify misconfig with array or as an educational tool. Full array stats provide the same info in ideal situations.
 
Joe_ said:
Is there a tester that does this that is affordable? I really don't know.
Click to expand...

I bought one of these panel testers and it seems to work pretty good. I've only used it with one panel of 400w, one panel of 405w, and another guy's panel of 445w and was able to aim them around at different times of day and get some good figures.

The 445w for my friend was a bi-facial so I was able to do some tests with him on the backside output facing the panel downward, and try out some vertical orientations..

Fixed link:
 
Last edited:
Unfortunately I was unable to use that link. It would not work. Could you repost it?
 
Here you go, will correct the other link too..



EDIT:
One word about it, the chips get warm in it after it's on for awhile, it has a temp sensor in it that shuts it down when too hot, you just have to wait a couple mins for it to cool for a bit and then it works again for while longer. I would take off the easy-access-plate cover on the backside that allows you to see the mosfets and if you blow on them it cools down faster. It works for quite awhile first but we were using it in August so it was hot out anyways, and would eventually shut down, because it is basically trying to burn-off electricity without any batteries to charge on, in order to test your panel output, so heat is a byproduct.
 
Last edited:
I was wondering if I could use the Victron smart shunt wired between the panel and a load of some sort to get an accumulated power output for a day? Would that work? 1 panel is 37 volts 7 amps approximately.
 
Joe_ said:
I was wondering if I could use the Victron smart shunt wired between the panel and a load of some sort to get an accumulated power output for a day? Would that work? 1 panel is 37 volts 7 amps approximately.
Click to expand...

Sure but it can't bulk-collect data from multiple simultaneous experiments like buying a TIGO CCA and compatible modules to grab data from multiple panels at the same time. Quadruple your productivity, as they say.

OTOH it's probably cheaper to use a workflow that tests one at a time
 
Are you doing fixed mount or something like mobile RV / camping mount?

In the latter case getting your hands dirty with experiments seems like it would pay off wrt better intuition on how to place them.

In the former case, see my previous note about just using modeling software.

Unless you also suspect that some of the panels might be degraded or whatever, then panel level monitoring or panel testing can tell you that / identify busted panels that might be dragging down a string.
 
Joe_ said:
I was wondering if I could use the Victron smart shunt wired between the panel and a load of some sort to get an accumulated power output for a day? Would that work? 1 panel is 37 volts 7 amps approximately.
Click to expand...

You'd need some kind of panel tester or charge controller with MPPT logic, capable of searching (variable load ohms) able to find Imp, Vmp, Mpp to find maximum watts... A static-ohm load can't do this..

That 37v is seen at open circuit, while that 7a is found at short circuit... You can look in the panel specs for the chart showing where Mpp is (Imp x Vmp)...
 
Last edited:
Also as post #2 said simultaneous testing is more scientifically proper.

It would suck if, after doing the really slow workflow of hooking up a shunt, collecting data for a day, and noting it down manually, your data turns out to be low quality / semi-invalidated because there were different solar conditions on different days of testing.
 
I like that tool.
I have a bunch of used panels that I am not certain of the condition of. But those aren't the ones I will be mounting at the moment.
But i do need to sort those out.
I'm doing something similar to an RV.. I 'm looking at mounting some new panels on a few shipping containers that are facing 168 south.
I can't tilt them south but need to tilt them 3 degrees or more east or west.
I can tilt the two main arrays west or east or 1 east and 1 west. I could also make the east container tilt west and the west container tilt east or vise versa. Also it is much cooler in the morning and very hot from 11:00 on so perhaps the cooler panels would put out enough extra that everything should point east? it's complicated. LOL
Samsonite801 said:
You'd need some kind of MPPT controller, capable of searching (variable load ohms) able to find Imp, Vmp, Mpp to find maximum watts... A static load can't do this..
Click to expand...
That is what I thought.
zanydroid said:
Also as post #2 said simultaneous testing is more scientifically proper.

It would suck if, after doing the really slow workflow of hooking up a shunt, collecting data for a day, and noting it down manually, your data turns out to be low quality / semi-invalidated because there were different solar conditions on different days of testing.
Click to expand...
I'm in the desert so clear sky's are more a thing than in many other parts of the country. But your completely correct.
 
Have you loaded up PVwatts (it’s a free website, pretty easy to use) and started punching in the numbers yet? That will clarify how much personal value you’ll get out of it…
 
Yes but how do you tell it that the panels are in pairs -12 north to 168 south, but tilted 3 degrees east-ish?
 
Last edited:
Joe_ said:
I like that tool.
I have a bunch of used panels that I am not certain of the condition of. But those aren't the ones I will be mounting at the moment.
But i do need to sort those out.
I'm doing something similar to an RV.. I 'm looking at mounting some new panels on a few shipping containers that are facing 168 south.
I can't tilt them south but need to tilt them 3 degrees or more east or west.
I can tilt the two main arrays west or east or 1 east and 1 west. I could also make the east container tilt west and the west container tilt east or vise versa. Also it is much cooler in the morning and very hot from 11:00 on so perhaps the cooler panels would put out enough extra that everything should point east? it's complicated. LOL

That is what I thought.

I'm in the desert so clear sky's are more a thing than in many other parts of the country. But your completely correct.
Click to expand...

I've found mostly, panel angle doesn't affect Imp hardly at all at mid-day Sun angles, it matters more at morning angles, late-afternoon/evening angles, and of course Winter angles. In the Summer between 10-4pm I can change the angle pretty far off and still get awesome output. But after 5pm it starts to matter more and more (as the angle going through atmosphere gets thicker and thicker).

For this reason, I just have half the panels pointing South (just a tinge SE), and the other half pointing more West, to catch the 5-8pm Sun better to help the AC so it lasts longer before eating into the battery as soon.

Mine don't have a very steep angle, maybe 18" higher on the rear than the front, and I leave them at that vertical angle all year, they do fine in the Winter, they still get full power during midday during Winter, but I am over paneled, twice as much as each charge controller can use.
 
Last edited:
I think I have it. I had a mental block on that one. I need to enter the array as being a landscape array with a azimuth 90 degrees from 168 south and a tilt of 3 degrees, etc.
I've been trying to deal with it from the portrait perspective because that is how I am able to mount the racking for the panels.
I'll give that a try. Thank you for the help.
 
You must log in or register to reply here.

Similar threads

Old_Skewler
Looking for "Seq. of Operations" mounting & wiring 6S2P panels on Roof: safety tips & best practice
Replies
11
Views
296
Hedges
Hedges
B
Solar Panel Wiring Configurations - 2p2s vs. 2s3p vs. 4s
Replies
8
Views
682
GooseF16
G
Will Prowse
Stacking and Angling Panels to Increase Output
Replies
18
Views
608
JRH
J
J
Paralleling slightly different panels to One Victron.
Replies
10
Views
407
JRH
J
M
Power performance warranty - how would you know?
Replies
3
Views
190
mciholas
M
Back
Top