Solar Panel: Volts but no Amps

[Goldie]

I have a Uni-Solar 32W Solar panel, about 4 - 5 years old, which is now failing to output any discenible current. In sunlight at open circuit, it produces about 18.8 volts. Having by-passed the boat's wiring and connected direct to the battery to eliminate any possible circuit problems, the DC current still reads Zero. I have taken it to Barden Energy (solar/wind/battery specialists and just up the road from me) and they have found the same result they are as /forums/images/graemlins/confused.gif as I am. If there is voltage, surely there must be some current? Sage advice eagerly awaited. /forums/images/graemlins/smile.gif Thanks.

 

[VicS]

[ QUOTE ]
If there is voltage, surely there must be some current?

[/ QUOTE ] There must be a high resistance somewhere. It could be within the panel itself, in which case it is cream crackered. It could be the blocking diode. Try bypassing that if possible and replace if found to be the trouble. It could be a connection but if there are no external connections you can get at then there is nothing you can do about it.

Most likely to be the panel itself.

 

[alan]

If the battery was fully charged then you would get no current.
Try connecting it to a known load of around the specified wattage; a car headlamp bulb is ideal ........... if you are going to do it without a regulator then I would suggest a truck bulb (24volts).

Maximum current should be around 1.7 amps (32/18.8) but you are unlikely to get this in England in the winter even with the panel orientated for optimum. From expereince I would expect you to be getting around 1amp to 1.2 amps. So, 1.2A X 18.8 volts = 22.5 Watts. So, a 24 volt bulb at around 25 Watts would be ideal. Connect this across the panel output with the ammeter (10 amp range) in line.

Alan.

 

[VicS]

[ QUOTE ]
If the battery was fully charged then you would get no current.


[/ QUOTE ] With 18.8 volts EMF you are still going to get a measurable current even if the battery is fully charged.

Regarding you calculations, you have not taken into account the internal resistance of a solar panel and I think you will find that the rated power is when the terminal volts is reduced to 15 volts by the current flowing. So that's 32 watts at 15 volts and 2.13 amps.

Nevertheless putting a load such as a car headlamp bulb across the panel with an ammeter in series will be a good test.

One additional thought though.. The regulator, presumably there is one for a panel of that size, has been taken completely out of circuit to eliminate that as the source of the trouble?

 

[Goldie]

Yes Vic, I by-passed the regulator and boat wiring and went straight to battery. I'll try the lamp test but having had the panel checked independently, I'm not holding my breath! Thanks for the thoughts.

 

[alan]

I just looked up the specs for that panel :
32 W:
Operating Voltage (Vmpp) 16.5 V

Operating Current (Impp) 1.94 A

Open Circuit Voltage (Vcc) 23.8 V

Short Circuit Current (Isc) 2.40 A

Open circuit voltage is quoted as 23.8V which seems quite different from what you were measuring; however, could be due to time of year, latitude, atmospherics e.t.c. This figure (Vcc) is usually quoted for laboratory test conditions. But maybe there is a fault within the panel; have you tried flexing the panel whilst measuring the volts to see if there is any change? I have identified faults using this method before....... but have never yet found a way to repair an internal fault!!!

A good suggestion was also made to try and measure without the blocking diode in the circuit. You may have to open up a little sealed "box" where the cable joins the panel to get at the diode (I'm not familiar with this particular panel).

Alan.

 

[Billjratt]

Ian, the panel's maybe not up to scratch if you were only measuring 18.8 volts open circuit. presumeably using a digital meter which has high impedance - it should be in the low 20s as Alan says. Peel open ANY bits you can get to and make sure the wires are in contact with the printed strips that link the cells.
I assume there's nothing visible in the way of damage on either side of the panel. I also assume it's two groups of nine series cells, in parallel ( if you know what I mean). So any break in the series direction in either group will halve the amperage available. You can test by blanking off one or more cells in either half of the array to see if a change occurs (with a bulb and voltmeter connected in parallel as a load ) Questions will be asked after homework is done! Bill

 

[Gunfleet]

For reference

I have a similar one and in bright sunlight this time of year it is putting out abt .9 of an amp.

 

[mikejames]

Re: For reference

I lost output from an old solar panel after about 15 years. This showed volts but gave no current.

I found the positive wire from the panel had rotted away between the terminal block in the connector box on the back of the panel and the panel.
The corrosion was inside some silicone sealant blob where the wire went through a backing plastic sheet on the panel. I was able to clean up, re-solder a wire and re-seal the wire.

 

[misterg]

Where exactly are you measuring the voltage?

It's got to be something like a broken connection between where you measure the voltage, and the end of the leads. If the panel was connected to the battery, you would measure battery voltage (maybe +~0.6v if there's a diode in between).

DO YOU HAVE AN IN-LINE FUSE HOLDER IN THE WIRES?

If so, I would put a pound to a penny that this is where the problem lies.

It does not lie 'up stream' of where you're measuring the voltage, so please don't rip the panel to bits.

Like you say, if there's volts, you should be able to get some amps, at least.

Note that there's nothing wrong with connecting a suitably rated ammeter directly across a solar panel - i.e. something capable of taking 2-3 amps for your panel.

0.02p

Andy

 

[Goldie]

Thanks one and all, plenty to think about there from brains that know far more elecktrickery than I. I trust you'll be coming down to mark my homework in person Bill? Please pass our best to C and TCC.

No fuses in the circuit as tested, no plug or connections, just leads from the panel. Thanks again one and all.

 

[misterg]

[ QUOTE ]
No fuses in the circuit as tested, no plug or connections, just leads from the panel.

[/ QUOTE ]

So if you're measuring volts at the panel end, but can't get *any* current, then one of the leads is broken or your ammeter is broken.

Andy

 

[William_H]

Start by cutting the leads at the panel (but long enough to reconnect) test again. As suggested an ampmeter straight across the panel +& - will test nicely. If it is still no good look for a way to open up the connection area you may find the connection of the wire to the diode if fitted or wire to the panel elements.
A suggested it is cream crackered if you can't find a wire break so don't be too reluctant to tear it apart. olewill

 

[corkonian1]

Barden Energy are not exactly solar/wind/battery specialists then if they cannot solve that one.
/forums/images/graemlins/laugh.gif

 

[Anonymous]

Two of their sales staff told me a load of utter codswallop re the solar panels they'd sold me, and about the advanced 3 stage controller, that isn't. Self-proclaimed experts? I think there are some key staff who know their stuff but they employ some virtually untrained people. They need to get rid of the bad ones, or train them, or limit them to making the tea and not advise customers.

 

[MarkJohnson12345]

I have recently bought a 20 watt panel.

It goes through a 12v controller, and according the the nasa battery monitor produces a massive 0.2 amps.

I hold my breath.........................

But it is winter and the boat is in the shadow of buildings in the yard.

The power input does keep the batteries up to scratch during the week, but doubt it would put a serious amount of amps back into the battery if they were low.

I think we ge a different kind of sunshine in the UK, especially in the winter. The sun goes through too much atmosphere to give alot of energy here.

I bet in Oz the 20 watter would give thousands of amps per second, despite all of the amps calcs.

Alternative energy is useful in the middle of the ocean or a river, but a poor relative if you have a 240 volt plug beside your pontoon.

 

[Goldie]

Thanks all, for your supplies and suggestions. Alas we shall never know if any of them would have worked because when I tried to collect the panel from Barden last week, they couldn't find it (the guy who had dealt with it wasn't there). Today they called me to tell me that it had been disposed of..... /forums/images/graemlins/mad.gif

Apologies were profuse, but I'm still /forums/images/graemlins/mad.gif

 

[alan]

That's pretty poor; I hope they offered you a replacement with a huge discount on price??

I had a Solara 225M fail on me after about 3 years which was out of warranty. Solara offered me a new one with a serious discount ......... 50% IIRC. /forums/images/graemlins/smile.gif


Alan.

 

[Anonymous]

Then they'd better give you a new one. It was their fault, it was in their care and it was not theirs to dispose of.

 

[Goldie]

Alan, Lemain, I agree! The problem is that the 32W panel is no longer produced (although Barden have offered me a 12W panel - poor substitute!). I shall pop down and see what they can do - the 32W flexible was ideal as it sat on the mizzen boom in use and stowed down alongside the cockpit dodgers whilst underway. I don't think anything else will do that. I haven't got space for a reasonably sized rigid one, although I suppose I could stow it in the quarter berth and try balancing it on the boom with ties to the corners - I doubt it would be very secure though. I'll let you know what they offer.