Solar System Trouble Shooting advice please

Submitted: Monday, Apr 22, 2013 at 13:35
ThreadID: 101816 Views:2739 Replies:6 FollowUps:6
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Decided to run a test on my solar panels on the 14yr old Trakmaster. One panel is probably 14yrs old and the other 10-12yrs at a guess - the panels are brownish in colour and not crystal glass and look about 80-100w each(maybe) and measure 740mm x 1366mm.
My system had and old "Sun Selector" regulator(not made these days) and feeds two as new Full river 105AH AGM batts configured in parallel. AC charging is via a 15amp Ctek.
So I switched off the Ctek and promptly forgot about it and found a while later that the batts were way down - and this through the summer - so I concluded something in the solar charging system was not working.
I recovered the batts and they are now cycling well after many tests.
All solar wiring and connections were checked and OK and I then measured the Open cct volts on the panels and that was 20.5 volts or so which I think is fine.
So I bought a new Prostar 30M reg and installed that. Did all the install and self tests and it seems to be working fine.
The Prostar is set with the "load" terminals set to "off" as nothing is connected here.
The Prostar is for battery recharge only.
After a week of testing,the batts got down to 12.1V before I bailed out and started up the Ctek again to avoid damage to the batts.The Prostar charging light was on but nothing was getting to the batts - the "solar amps" read ZERO throughout.
The solar open cct volts are still around 20V and when the Prostar charging light was "on",the solar volts and batt volts were identical meaning the panels were connected through but I should have had 14V or so if the solar was PWM charging through the reg.
Any thoughts from anyone?
Can the panels be faulty even if they show the right open cct volts?
How can I test this before investing in new panels?
Any help appreciated
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Reply By: Member - J&R - Monday, Apr 22, 2013 at 14:28

Monday, Apr 22, 2013 at 14:28
The panels may have voltage present but not be able to supply any current. Hook up a load to the panels without a regulator (an old headlight bulb that still works will do) and see if it illuminates.
AnswerID: 509535

Follow Up By: Member - Ron B (VIC) - Monday, Apr 22, 2013 at 22:02

Monday, Apr 22, 2013 at 22:02
Gday mate,
thanks for that suggestion. I'm going to try this tommorrow using some old bulbs I have. If I can't find a headlight globe at 55W,I'm sure I can find a few indicator globes at 21W to make a suitable load.
FollowupID: 787465

Reply By: CampingTechAust - Monday, Apr 22, 2013 at 21:51

Monday, Apr 22, 2013 at 21:51
Hi Ron,
Could you please check if your old panels have a blocking diode installed?
Your new regulator doesn't require them to be installed.
If the panels have the diodes installed, I would expect them to be in the junction box on the back of the panels. With the panels connected to the regulator, can you measure the voltage on either side of the diode - hopefully you can get to both terminals. I would not be suprised if you get 14V on the regulator side of the diode and 20V on the panel side. They could be getting warm too.
Try that first before you write off those panels.
Basically I think after reading the manual of your regulator and from your description that the diodes have gone high impedance. With the panels open circuit, they will present the regulation 20V every day of the week. With the panels connected to your regulator, all of the "power" is being lost over the diodes.

Hope this Helps
Camping Technologies Australia
AnswerID: 509562

Follow Up By: Member - Ron B (VIC) - Monday, Apr 22, 2013 at 22:13

Monday, Apr 22, 2013 at 22:13
Gday Jason,
hadn't even considered the implications of technology advancement over those past 12-14yrs,and yes,the Prostar does not need a blocking diode in the panels - but maybe the old regulator did?
I have no paperwork on the old reg and neither did Trakmaster and I found the company in the US doesn't exist any more when I tried to contact them for a user manual.
I had the panels off about a year ago looking for a roof leak and had to disconnect them - I can't remember seeing a diode in either of the control boxes BUT,it might be there as I wasn't looking for it.

I'm going to try and put a 4 or 5 amp load across the panels tommorrow (with the regulator disconnected) as suggested above
and see if there is any result but I don't expect one).
If that doesn't work, I'll remove at least one panel and have a look for that diode.
Thanks for the input
FollowupID: 787468

Reply By: Member -Ted (Vic) - Tuesday, Apr 23, 2013 at 08:35

Tuesday, Apr 23, 2013 at 08:35
Hi Ron

The blocking diodes are there to prevent backfeed when the panels are in series and one of them is shaded it prevents the sunlit panel feeding back into the shaded panel. The diode is connected across the output of the panel so it doesn't have a panel side and a regulator side. I would suspect the panels are not supplying any current even though the voltage would appear to be correct. With the panels wired in parallel the diodes do nothing.
I think by applying a load with a globe or resistor is the way to go.

My two cents worth
Good luck
AnswerID: 509589

Follow Up By: Member - Ron B (VIC) - Tuesday, Apr 23, 2013 at 09:23

Tuesday, Apr 23, 2013 at 09:23
Thanks Ted,I'm learning a bit more each time.
My panels are definitely wired in parallel for a 12v system.
Jason's suggestion above would therefore seem irrelevant,ie even if the diodes are fitted,they are across the output(the only place they can be of course) and if the panels are in parallel,the diodes are irrelevant. I was confused by Jason's comment of measuring voltage at the "regulator side" and "panel side" of the diode when I know each panel has only one pair of wires connected and the diodes have to be connected across those if they are fitted.
FollowupID: 787497

Follow Up By: CampingTechAust - Tuesday, Apr 23, 2013 at 14:32

Tuesday, Apr 23, 2013 at 14:32
Hi Ron,
Apologies for not being clear in my descriptions.
There are 2 types of diodes used in solar applications - blocking and bypass. Blocking diodes are used to stop current flowing backward through the panel at night and are installed in series with the panel. Bypass diodes are used to allow the current from a fully lit panel to bypass the high resistance presented by a panel that is shaded. Bypass diodes are installed in parallel.
In my post, I was referring to the blocking type (as per your manual) which are in series. Being in series, the Anode of the Diode will be connected to the positive terminal of the panel (inside the junction box) and the Cathode will be connected to the positive lead going to your regulator (also inside the junction box).

I would try Ted's idea first as that is much easier than mine, but I am expecting that you may not get much if any light from a globe. If this is the case, open up the junction box, identify the type of diode you have, if it is wired in series or parallel and which terminal is the anode and which terminal is the cathode. If it is in series, happy days, keep reading below. If not, then my idea isn't going to work for you and I'm back to the drawing board!

If in series...
The "panel side" is the anode and the "regulator side" is the cathode. Given the age and size of your panels, I also wouldn't be surprised if you have the old style diodes that are a little black cylinder with a white band at one end and the leads sticking out of either end. The white stripe is closest to the the cathode terminal. (sorry if this is obvious to you).
With the panel connected to a load, measure the voltage on both sides of the diode. If the voltage is more than 1 Volt different (I am expecting you will read close to 20 Volts different, the diode has failed. Go to an electronic component retailer and buy an new one (rated for the max current of your panel) They should only cost you a few $ at the most.

Hope this helps

FollowupID: 787532

Reply By: oldtrack123 - Tuesday, Apr 23, 2013 at 11:53

Tuesday, Apr 23, 2013 at 11:53
Hi Ron
It is quite possible to get the open circuit volts you measured , but the panels can still be faulty
I would suggest you check the short circuit current
Disconnect the panels from each other & the reg

Then with your multi meter set for 10A DC check the SHORT CIRCUIT current of each panel
IF the panels are 80W, it should be around 4A <5A in bright sun!!

AnswerID: 509597

Follow Up By: Member - Ron B (VIC) - Tuesday, Apr 23, 2013 at 15:41

Tuesday, Apr 23, 2013 at 15:41
Gday Peter,
I followed your suggestion with the panels demounted and even with the terminals on the panels fairly RS,I managed 3.25A on one and just under 3A on the other - telling me the 60W panels are working OK and will work better when I clean things up
See below for full story
FollowupID: 787548

Reply By: Member - Ron B (VIC) - Tuesday, Apr 23, 2013 at 16:06

Tuesday, Apr 23, 2013 at 16:06
Hi all,
first a big thanks to all who replied and made suggestions - I've followed them ALL and I sure know a lot more about solar than I did before.
The answer to my problems turned out to be a fairly simple one but one that I didn't expect.
First some facts and measurements (with the panels demounted off the van):
- my panels are only 60W and 64W. Manuf 1997 for one and 2003 the other
- no bypass or blocking diodes fitted in the control boxes
- Open circuit panel voltage measured at the panels 19.5 - 20.5 volts(bit more in full sun)
- short circuit current panel 1 is 3.25A,panel 2 is 2.95A (part shade,crap terminals)
- I can light a 21W indicator bulb brightly off each panel (more in better light)
- my junction box terminals are stuffed
- I conclude the panels are old but still OK

And now the answer:
In my initial follow up to Jason I mentioned chasing down a roof leak 12 or 18mnths ago which I found and fixed.
This filled the van ceiling with water and sagged the roof inside and out - I can't do anything about this "sag" and with me getting up there occasionally,even with a load spreading board,the sag is very noticeable.
A test this arvo with the van levelled and a garden hose showed the water pooled on the roof to about 1/2" - enough to creep up the sides of the junction boxes on the panels.I had sealed them well incl cable entries/exits when I refitted them but didn't allow for the screws - where water must have wicked up.. My boxes were 1/2 full of water and there were signs of arcing with some terminals destroyed.Splashing or condensation I guess.
I'm now working on trying to repair the terminals but I will direct-connect the panel outputs to the solar feed wires and use what's left of the terminal blocks to anchor the lugs.
I'm also working out a way to raise the panels up another 25 - 30mm to get them away from any pooled water.
My wattage is only total 124W and that will have to do for now.
I'll upgrade or buy a portable panel set for the planned big trip as I run a 110L Waeco F/F and an Engel 38L as a freezer.
Any last observations welcome
AnswerID: 509614

Follow Up By: Member - J&R - Tuesday, Apr 23, 2013 at 18:00

Tuesday, Apr 23, 2013 at 18:00
Forget a portable setup. Forever setting up, chasing the sun, tripping over cables, packing down, packing away and get the idea.

Just buy a new panel, say 200 watts and mount it a little higher. The difference in output with a modern panel/regulator is worth the expense. I'm in the process of putting 600 watts on an offroad trailer. Will be totally self sufficient for the foreseeable future.
FollowupID: 787562

Reply By: CampingTechAust - Tuesday, Apr 23, 2013 at 23:45

Tuesday, Apr 23, 2013 at 23:45
Hi Ron,
I'm glad you got to the bottom of your problem.
I was reflecting on Ted's comments about the Bypass Diodes helping when a panel is in shade and given that you will soon be in the market for new panels, I thought I would post one final comment.
I work for Silcar Energy Solutions and our workshop in Perth is flat out with construction of large solar arrays for the National Broadband Network. So I went and stuck my head under a 24 panel array that had just been completed. The 80 W panels that we are using have 2 bypass diodes installed. This is because the panel has been constructed as 2 separate halves at 40W each and wired in series. The BIG bonus for us campers is that if one half of one panel goes under shade, you won't loose the entire panel. There is a down side with panels wired in parallel though. The panel that is in shade will present a lower overall voltage which will drag down the second panel that may still be in full sun.

So, if you can get a panel constructed in this way, you will get the best performance possible under marginal light conditions. If your regulator allows, you would do better to wire the panels in series, then a panel in shade won't pull down the second.

Camping Technologies Australia
AnswerID: 509640

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