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Forum Index : Solar : tricky solar problem
| Author | Message | ||||
| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Here's one for a Monday.. No solar output ... Plenty of volts -66.7 . But no output,very strange,oh a very little .1 amp ,but really nothing. I've tried disconnecting /reconnecting the feed cables . but haven't disconnected/reconnected the panel junction box's cables yet. So, this is why my regulator wasen't showing a solar input ??.(maybe it's OK) I tried a dummy load ,,no difference ,no output.. I tried a DC clamp meter ,no output, just that slight .1 amp S , what do you think .. blocking diodes?? ,but how come I get 66 volts ,,but next to zero watts ,just dosen't make sense. 4X 220 watt sharp panels configured to 48 volts , has been down for ,say 2 months, but was working for 2 years before. Bruce Bushboy |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Big splat of bird sh*t on one cell? A whole panel's output current is only as good as its weakest cell. Volts will be OK. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Can have the same symptoms for a degraded connection or faulty wire in a solar panel circuit, usually on the negative. Pays to be slow and methodical, I find if I dont I can miss the problem, for hours!  I'm confused, no wait... maybe I'm not... |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Bruce That's about the normal unloaded voltage of a 48 volt system, Have you tried bypassing the regulator as a similar thing happened to mine and it was the PWM regulator went down so it showed the voltage of the panels but stopped feeding the battery. My friends setup went down like that also and we traced it to a faulty cable when we cut it open there was a corrosion spot in the middle of the cable that caused high resistance and melted the remaining conductors, inside a conduit it wasn't noticed until we pulled the cable out. You can connect a ammeter directly across the output of the solar panels early in the morning and watch the amps rise as the sun comes up, be sure to put in a switch to open the circuit so you do not overheat wiring with the short if all is OK. The high voltage reading would indicate to me that there is an open circuit somewhere from the regulator to the batteries as if it was connecting to the batteries the voltage couldn't go that high. All the best Bob Foolin Around |
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| Pete Locke Senior Member  Joined: 26/06/2013 Location: New ZealandPosts: 181 |
Light bulbs are about the best invention for testing all sorts of power related things. I don't have any solar set up, but if it was me I would series together two 24v (or whatever combination will give you the right voltage for your panels) high wattage automotive lamps (brake lights are good) and bung them across the panel output leads. You will know straight away visually in which direction to start fault tracing. No light, head towards the panel. Plenty of light, off towards the controller. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Looks like Bob get the kit-cat prize ! Corrosion is the suspect. I have not drawn the cables out of the conduit yet , but suspect ,after multimeter checks and a buzzer ,that it's the problem. 16mm square cable ,single insulated, run in 40mm irrigation piping.. Let you know when I pull them out .. Thanks for your interest, Bruce Bushboy |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Bob, if there is any wiring overheating with that test then the wiring is seriously undersized. I always test a suspect solar panel by first disconnecting it from everything and then shorting it out with a suitable amp meter. I do that test at lunch time in full sun. The panels do not mind being short circuited that way and the max short circuit current is only slightly higher than the max power current. Its probably better not to use a switch to open the circuit as at 60V there might be some arcing at the switch contacts. Klaus |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Klaus If I am testing panels for balance output I do the test at midday also, but when testing a whole array I like to do it in the morning and watch the output rise and watch for flickers on the ammeter as that could indicate a loose connection or a dry joint somewhere in the system, I do use a switch because it allows you to control the experiment without the risk of a shock as 60+ volts DC can be lethal under some circumstances I use a panel with a 300 amp battery isolater switch and shunt 300 amp meter and a 20 amp digital meter for testing panels for balance simple set up but it works and is better than hay wired meters like I used to do. I have managed to weld up a couple of lower rated switches so the bigger the better, my first one had a 500 amp starter solenoid off a diesel engine on it and it worked real good, but I lent it to someone and can't remember who it was, bugger, more Brami required. Right on the wiring overheating but we do cut corners at times and the extra 20% amps when shorted can make the magic smoke arise and a poor contact heat up and blister the skin. All the best Bob Foolin Around |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
I removed that suspect 16mm square cable from the duct --- Yep, Bob was correct,corrosion ... Here's a pic ,will cut the sheathing to get a look at the copper corrosion. Bruce 
Bushboy |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I sometimes see a corrosion problem with satellite cabling that you could probably relate to. The cables are designed so that 18 volt DC can be injected into the outer braid to power the signal pickup (LNB). A parrot has a little nibble on the plastic sheath and the water is sucked in what seems like an impossibly tiny crack. Sometimes I have seen it fill the entire cable run with water and the DC power just eats everything away. I am amazed at how far gone some of them are before the TV signal drops out and I get the emergency phone call. I'm confused, no wait... maybe I'm not... |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks for that Yahoo, I used to cable outdoor microwave units ,sometimes 100 or more feet up the tower. These were fairly thick coaxial cable ,maybe as thick as your little finger. I've taken the connector off at the bottom of the tower in the radio shack ,and guess what, --? I've been flooded with water coming out of the cable .. And, you are right , the cable, connectors, and even sometimes the radio inside is wet and corroded.. DC is fed to lnb's ( low noise block downconverters) just behind the parabolic antenna .. This is necessary to convert ( downconvert) the microwave frequency to an intermediate frequency suitable for coaxial cable transmission--(just for the interested forum readers.) Bruce Bushboy |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Bruce The normal heating and cooling of the conductors in a humid environment causes the atmospheric moisture to condense and can be very corrosive when in a enclosed duct, I always found it better to lay cables above ground and exposed, as it ventilates and prevents the build up of the pure H2O in a confined space. The only other way is to pressurize the conduit with an inert gas, not to easy in our applications. All the best Bob Foolin Around |
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