Solar System Trouble Shooting advice please

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.

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
Jason
Camping Technologies Australia
https://sites.google.com/site/campingtechnologiesaustralia/

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

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!!


PeterQ

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
Rgds
Ron

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.

Cheers
Jason
Camping Technologies Australia
https://sites.google.com/site/campingtechnologiesaustralia/