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Solar Panels Again

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Posted

I'm looking for a bit advice from all you solar panel experts because I'm not sure if it's working properly.

I have a briefcase type 15watt panel and I used it the other week for 7 nights (from Friday to Friday) off electric on a CL. My battery's 85amp.

Late on the Sunday afternoon I checked the battery with a multimeter and it was reading 12.35 volts. From then on I used my LCD TV (8 watts) for approx 4 hours each evening plus my water pump once daily for washing/shower and once daily for my dishes. I also used the kitchen fluorescent light approx half an hour a day plus one reading light for maybe 1-2 hours a day.

On the Wednesday morning I checked the battery and it was 11.75 so I decided to hook up to the car and ran the car for about 40 minutes. After that the battery was just over 12 volts but in the evening - before using anything - it was back to about 11.75. Anyway, I left it after that and late on the Thursday night the power was non existant no.gif When I checked the battery on the Friday morning it was about 10.85 yikes.gif

Any time I checked the battery the multimeter gave the same reading with the croc clips of the solar panel attached to the battery as without the panel attached. When I checked the croc clips of the panel when it wasn't attached to the battery, the panel was usually giving readings of 20-22 volts so I assume when it didn't give such high readings when it was attached to the battery, it must have an inbuilt system to stop it overpowering the battery. emdunno.gif

Is there anyway I check if the blocking diode on the solar panel is working or not? or has anyone any ideas because I really don't think the battery should run down like that with the power I was using. It's a panel by PDQ Omis but it didn't have any instructions etc. since I bought it as an ex-display model last year.

Sorry for the long post but I was trying to give as much info as possible to see if anyone has any ideas. idea_1.gif

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48 answers to this question

Posted

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Dot,

Are you sure that your TV is only 8 watts - cos if it is it must be rather small !

Does your multimeter measure current ?

If it can measure up to about 2 amps (bit of safety margin in there !) try connecting your panel with the meter in series with one of the connectors so you can get an idea of the current the panel is providing.

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Posted

Are you sure that your TV is only 8 watts - cos if it is it must be rather small !

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Posted

Dot, I've still to get myself a Solar panel, but I'll try to give a reply even though I have no experience of these things; just the fizzics!!

A 12V battery showing only ~10.8V is practically DEAD. Your TV will be way over 8 watts (Unless it's tiny). The fact that your battery voltage just went down and down shows that you were drawing far more power from the battery than you were replacing.

The best way to see if your solar panel is charging the battery is to measure the CURRENT flowing from panel to battery, when the sun is shining. Max. current should be ~0.9amps flowing from panel to battery. When it is dark, there should be NO current flowing at all. The diode is to prevent current flowing out of the battery and into the solar panel (at night). It does sound as though your diode may be faulty and the panel is draining current from the battery at night.

Best of luck,

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Posted

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Connect the black lead of your multimeter to the positive (red?) lead of the panel and the red lead of the multimeter to the positive terminal of your battery (providing the multimeter can cope with 2 amps )

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Posted

Thanks folks, I'll give it a go tomorrow.

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Posted

One other thought - are you using a charge controller between the panel and the battery??

THere's one HERE if you want a look it. The energy guru's at work reckoned anything over a 10W panel should have one to stop problems with the battery (didn't say what problems though!!)

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Posted

"Can you get beer from a Duff battery?"

Homer Simpson (not the poet)

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Posted

Hmmm now I'm wondering if the panel's really working much at all unsure.gif

I've checked the back of the telly though (pic of TV attached) and discovered it's actually 15Watts so I've been using about double the power that I thought yikes.gif The telly was a replacement for a faulty one that was 8watts and I'd assumed the replacement was the same blushing.gif I still wonder though if the power I used could've been supplied by the battery without the panel at all so maybe the panel's not working emdunno.gif

I put the solar panel out today and left it for about half an hour then I tried the multimeter on amps and connected the black lead of the multimeter to the red lead of the panel and the red lead of the multimeter to the red terminal of the battery (I disconnected the elec hook up first). When I switched on the multimeter and kept it all attached for a minute or two till it seemed settled, the multimeter reading kept flickering between -0.02 and 0.02. From that I'm assuming that there's maybe only 0.04 coming from the panel.

Neil, I had wondered about a charge controller because I'd just come across a site yesterday advising to use one above 10watts too. I saw that one on Ebay but I was keeping my eye on this one but I'm not sure about the panel now.

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Posted

And here's a pic of the multimeter when I had it connected to the panel and the battery.

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Posted

"Can you get beer from a Duff battery?"

Homer Simpson (not the poet)

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Posted

Unfortunately our panel is in the van - about 10 miles away - otherwise I'd have repeated the M/meter experiment tonight to compare. If I get a chance over the weekend I'll take the meter over to the van and give it a whirl for you!!!!

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Posted

Thanks very much Neil thumbup.gif

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Posted

wine.gif

Dot,

Assuming that it was a half decent day I think you should have had at least 0.5 amps ..... I suspect that your panel may have a problem.

The first thing to do is use your multimeter to check for continuity on the cable, if that's OK then check the connections at each end.

For the continuity check disconnect both ends of the cable if possible (if not just disconnect one end). Switch the Multimeter to Ohms (Might show an Omega sign) connect one of the multimeter leads to one end of the positive cable and the other lead to the other end of the cable. If the cable is OK you should get a reading that's close to zero e.g. 0.3 ohms (probably less). Repeat the test for the negative cable. If the cable is OK and the connections are fine then you may have an issue with the blocking diode - can't really help there unless I can see how it is put together.

Good Luck

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Posted

Thanks very much for tomorrow's homework PB biggrin.gif

It was lovely and sunny when I tried the panel today so I'll try these instructions tomorrow.

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Posted

Finally got round to checking the cable and it's OK, so has anyone any other suggestions? Please? emdunno.gif

I'm really thinking it's probably not worked at all since I bought it but I didn't have a clue how long my battery should last anyway and, of course, the panel's over a year old now cry.gif

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Posted

Hi Dot. That's a fine picture of the meter.

Back to the panel. Can you get at the diode? It should be in one of the leads from the panel - between the panel and the crocodile clip or it could be attached to the panel.

If you can, then put the red lead on the meter to the other side of the black one on the meter, as shown in the picture, and set the dial three positions from 'OFF' That is the omega sign and the meter will then read OHMS.

Put the ends of the leads together and you will have a very low reading, perhaps about 0.2 or 0.3 OHMS. That is the ressistance in the leads.

Now, without touching the metal of the probes, put the leads on the diode, one on either end and wait a few seconds for the meter to settle. Note the reading. Watch for a K or M after the figure

Then connect the leads to the diode the opposite way round to your first test, that is swap the red and black to black and red. Note the reading. Again watch for a K or M.

Post it on hear and I can tell you if the diode is OK or not.

Sorry if I am teaching grandma to suck eggs .....

Dave

Dave

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Posted

Sorry if I am teaching grandma to suck eggs .....

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Posted

The one in the background must be one of the biggest though. Howe many watts is it I wonder? emdunno.gifemdunno.gifemdunno.gif

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Posted

Hi Dot.  That's a fine picture of the meter.

Back to the panel.  Can you get at the diode?  It should be in one of the leads from the panel - between the panel and the crocodile clip or it could be attached to the panel.

If you can, then put the red lead on the meter to the other side of the black one on the meter, as shown in the picture, and set the dial three positions from 'OFF'  That is the omega sign and the meter will then read OHMS.

Put the ends of the leads together and you will have a very low reading, perhaps about 0.2 or 0.3 OHMS.  That is the ressistance in the leads.

Now, without touching the metal of the probes, put the leads on the diode, one on either end and wait a few seconds for the meter to settle.  Note the reading.  Watch for a  K  or  M  after the figure

Then connect the leads to the diode the opposite way round to your first test, that is swap the red and black to black and red.  Note the reading. Again watch for a  K  or  M.

Post it on hear and I can tell you if the diode is OK or not.

Sorry if I am teaching grandma to suck eggs .....

Dave

Dave

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Posted

Dot,

Once you get your panel sorted Towsure do a charge controller for ?24.95.

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Posted

. . . . .

At long last I think I've done what you asked  laugh.gif

The resistance in the leads settled at about 0.1 to 0.2 OHMS.

It's hard to see which lead in the diode is red and which one black but, if it makes a difference, I think I put the black from the voltmeter to the red of the diode and the red from the voltmeter to the black of the diode and the OHMS reading settled at about 2.299 to 2.301 M When I put the black voltmeter cable to the black of the diode and the red of the voltmeter to the red of the diode it didn't give any reading at all. The voltmeter never moved at all  emdunno.gif

Is that any help?

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Posted

Dot,

Once you get your panel sorted Towsure do a charge controller for ?24.95.

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Posted

Sorry for only picking up on this thread now, Dot, but it so happens I've been fiddling with my Solar Panel, today, making a fancy suction cup (Vacu-rak) platform frame to mount it on the roof of the 'van, without drilling holes!!.  When I've got it sorted I'll put some photos on here.

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Posted

wine.gif

Sounds like the same thing I did in November - pity I haven't been off mains since then !

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Posted

Dot et al.

I got the frame for my solar panel sorted today (well nearly) see below.

user posted image

There are some other photos here.

The vacuum suction pads are American (From GT Towing) and are designed to carry loads on a car roof or boot (trunk) lid. They are very powerful and, with 4 attached, I think the panel should be OK, certainly on the stationary caravan; not intended to travel with the panel on the roof.

When it was sunny this morning, I tested the voltage output of the panel.

Horizontal to the ground it was 20.4V and tilted towards the sun 21.3V; thus with a clean panel there's only an extra volt obtained by tilting the panel to the sun.

However, I've designed the frame, to allow the panel to be tilted; not so much for extra output, but more to allow water etc. to easily run off. A flat panel, like the roof, will get algae, moss and general grot settling on it, seriously degrading its performance.

I haven't got it actually connected into the'van yet, as I need to route some wiring around the 'van to the Solar controller and battery.

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