Have I blown my solar panel?

[richardabeattie]

I have a small 12v solar panel for keeping my equally small battery topped up but took it home to also top up my car. Demonstrating sheer stupidity I then forgot the instruction to disconnect it from the lighter socket before turning on the engine. Now I can't work out whether I've written it off. When I connect a multimeter to its plug in sunshine the meter briefly reads 19v and then displays 1! What should it read?

 

[GrahamM376]

Many cigar lighter plugs have a fuse which can be problematic, does that have good contact? Did the plug come with the panel - any control board in it? Suggest checking voltage on wires before the plug, 19 -21v in good sun OK.

 

[richardabeattie]

There's just a wire from the solar panel to the male cigarette lighter style plug and that is a sealed unit with no sign of a fuse. Any circuitry must be in the panel itself. Of course the 19v reading across the plug is in a no load situation. But I don't know why after briefly showing 19v the multimeter then shows 1.

 

[RichardS]

There's just a wire from the solar panel to the male cigarette lighter style plug and that is a sealed unit with no sign of a fuse. Any circuitry must be in the panel itself. Of course the 19v reading across the plug is in a no load situation. But I don't know why after briefly showing 19v the multimeter then shows 1.

The panel should have some diode protection built in to prevent against excess reverse current although, to be honest, if your cigarette lighter socket is pemanently live, I can't really see why starting the car, which would cause a drop in voltage across the battery and then an increase to 14V-ish, would damage the panel anyway.

The meter should continue to show 19V as long as the panel is in sunlight and I would be surprised if it could be damaged in a way that only affects it after a while. What happens if you hold the probes on the car battery terminals?

Richard

 

[CCJ]

I have a small 12v solar panel for keeping my equally small battery topped up but took it home to also top up my car. Demonstrating sheer stupidity I then forgot the instruction to disconnect it from the lighter socket before turning on the engine. Now I can't work out whether I've written it off. When I connect a multimeter to its plug in sunshine the meter briefly reads 19v and then displays 1! What should it read?

Use a higher range on your MM

 

[richardabeattie]

CCJ has it! On the higher range the no load reading is steady at 22v so the panel seems to have survived. Many thanks.

 

[Pagetslady]

The fuse in the cigarette lighter is in the center pin it unscrews usually the fuse is in there.

 

[lw395]

CCJ has it! On the higher range the no load reading is steady at 22v so the panel seems to have survived. Many thanks.

For a full test, repeat that with a bit of load on the panel
We used to test 10W panels with a 2W or so load, using our 'not calibrated' 600W floodlight.

 

[richardabeattie]

As I said the plug is a sealed unit and cannot be opened.

 

[lw395]

As I said the plug is a sealed unit and cannot be opened.

Is that a challenge? Dremel, scalpel,solvent, brute force?

 

[VicS]

Is that a challenge? Dremel, scalpel,solvent, brute force?

Why bother?

It ought to be fused therefore chop it off and fit a fused one! Unless the socket is suitably fused

 

[agurney]

Why bother?

It ought to be fused therefore chop it off and fit a fused one! Unless the socket is suitably fused

Is it possible the cigar plug has a built-in regulator?

 

[richardabeattie]

As I said - I now know the panel has not been damaged so why would I want to dismember or chop off the plug?

 

[VicS]

As I said - I now know the panel has not been damaged so why would I want to dismember or chop off the plug?

To fit a fused one if the wiring to the socket is not appropriately fused. Or if its a bog standard cigar lighter socket and plug to replace with something better.