Low voltage output

[Hymie]

I have a motorhome with a Kyocera 12 volt 80watt 10 year old solar panel for recharging the batteries. It appears not to be working and I have the following readings: In full sun with nothing attached it gives approx 4.5amps at 10volts. I suspect that as the voltage out is lower than the battery volts the regulator is not allowing any charge to take place. Also having disconnected the panel the batteries now charge (on electric) to a higher voltage than they had before, so could the panel or the regulator have been affecting this? The blocking diodes appear ok at hi impedence one way and approx 1.5M ohm the other (rather high?). What can go wrong with a solar panel? can it be cured?

[Mike90250]

your blocking diode should be a few ohms in one direction, and 1.5M ohm the other direction. Some meters have a diode test position, since it can take 2 VDC to fully turn on some diodes.
If you have a charge controller, it usually has a blocking diode built in, a 2nd one is pointless.

How old are your batteries. 10 V is 2v less than 12V, and it could be a cell has died.

Can you attach a regualr charger, to get your batteries back up - 10V is dangerously low, and will destroy the battery quickly.

[Hymie]

Thank you for your reply.

Yes the diodes are giving odd readings I agree with you but they do read less in one direction than the other. Normally faulty ones are either S/c or O/c. I wonder if these are some type of high speed, high current diodes which read higher than normal or as you say I need a diode test position. Mine has a transistor test but not diode and the slots are too small for the diodes anyway.

The batteries are absolutely fine when charged by normal means (14volts), and , as mentioned achieve a higher charge with the panel disconnected.

It just that the panel gives out current but at 10 volts. I have tried another meter and that was the same.

[Mike90250]

you may have had a panel failure. Can you examine it - look for hairline cracks or lifted bond wires (view thru the front glass)

[astrayan]

In full sun with nothing attached it gives approx 4.5amps at 10volts.

Typically, when a panel has nothing attached, it emits no current You aren't measuring current and voltage at the same time. You are measuring short circuit current first, and then measuring open circuit voltage of 10V.

Your panel could be like mine, ie: half of it is dead, and the bypass diode allows the half that works to be measured as 10V, or 4.5A.

[Hymie]

The readings I have taken are off load, therefore disconnected from the regulator pcb, battery, etc and I would have expected around 16 - 20 volts for a 12 volt board. I cant understand if half the panel is dead (which is what the volts are telling me) how I still get 4.5 amps. Very stange. Upon closer inspection there appears to be no damage to the panel at all and all a nice even blue appearance.

[astrayan]

You are getting half the voltage, but the current will remain the same, because each cell outputs 4.5A.

It's because panels have 3 wires for output in the junction box. This allows -11V, 0V and +11V access to the panel bus.

When the current goes through a diode, when you short circuit it using an ammeter, the diode clips off 1 volt, as the current goes past the dead half.

If you could subtract one cell from the array, you'd measure about 4.5A front-to-back.

As I said in another thread, I have lost 5 out of 7 BP panels this way.

[Hymie]

Firstly thanks to everyone helping me with this.

I had not realised that the board was split as you say and now testing the board show that one side is dead and the other is ok. At least this proves the board to be faulty. I spoke to another camper recently who said he thought solar panels were guaranteed for 20 years, does anyone know about this please?

PS Sun shining in spain - shame I cant recharge batteries!

[astrayan]

does anyone know about this please?

I believe that all products are designed to break just after the warranty expires, so you will find your Kyocera panel warranty is 6 months less than the period it took to break.

Old panels had a 10 year warranty. New panels have 20.

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By the way, when I rang up dealers, looking for ideas, they said that the bypass diodes can sometimes be faulty and form a dead-short. In order to properly diagnose your problem, the diodes must all be clipped out.

I don't know if anyone can verify that this is a real problem that happens often, since in 12V systems the diode has never had any current pass through it. (Unless you have been short circuiting the panel and partially shading it.)

[Hymie]

All ok now

I Just want to thank everyone for their help regarding my Kyocera solar panel. Also to let you know that Kyocera have been absolutely brilliant and following my initial email to them via their web site have replaced my solar panel under guarantee with no charges to me at all. Now all is well. Many thanks again to all - especially Kyocera.

[john123]

you may have had a panel failure u should chk it