Decorative Solar Lamp Question

[mmartell]

Not sure where this question should go so I posted it here...

I have one of those decorative solar lamps, heavy cast head goes on a metal pole, hasn't worked in some time so took it down to have a look at it.

It has a fairly large array of panels compared to the single panel sold in those cheapo solar lights sold in the dollar stores. But when I measure the voltage coming off the panel in full sunlight it struggles to reach half a volt. In comparison the cheapo dollar store ones easily put out 2.3 volts. I know they are different designs and the one I have uses a 4v 4ah SLA battery and a much more complicated circuit board but my question is... is the solar array dead or was there a time that half a volt was the expected output ?

I was hoping to use the array and replace the circuit board (not sure if it's working) and the old SLA battery for a couple nicads at minimum or lithium even better. The single led inside still works.

[mmartell]

Re: Decorative Solar Lamp Question

Here's a pic with my lamp and the dollar store one above it.

[Curious.George]

Re: Decorative Solar Lamp Question

But when I measure the voltage coming off the panel in full sunlight it struggles to reach half a volt.

Are you measuring the unloaded output of the panel? Or, is the load possibly dragging the output down?

[mmartell]

Re: Decorative Solar Lamp Question

Unloaded for both, straight from the solar panel.

[sam_sam_sam]

Re: Decorative Solar Lamp Question

Show a picture of the inside of the solar light and the back side of solar panel

[eccerr0r]

Re: Decorative Solar Lamp Question

if any of it is in shade, it could drop down to 0.5V, so that could be one thing...

[redwire]

Re: Decorative Solar Lamp Question

Water getting in kills the interconnects or they bake in the sun and oxidize, and sometimes a cell can get cracked from hail. You likely have an open circuit.
I would load the (multimeter) with say a 1k resistor and in normal light measure the voltage output at various points in the array. There's cracks in the black plastic... which means water gets in.
It must be a series and parallel combination. I see 12 cells, and go with about 0.5VDC each, so maybe 3p4s? OOPS it's for a 4V SLA so likely all in series to give 6V.

I was tinkering with a couple Ikea solar lights. With one AA NiMH cell the big one is 6 cells in series for about 3V minus the schottky diode, so it's extra voltage/charging in the Ikea Solvinden table lamp/cone. But a piece of junk as the cone is frosted white and masks the sun really bad. Got it on sale to tinker with. It also lights up way too early.

Usually I see four cells in series (~2V minus schottky diode) to go with one AAA battery i.e Ikea Solvinden pendant light.

[mmartell]

Re: Decorative Solar Lamp Question

if any of it is in shade, it could drop down to 0.5V, so that could be one thing...

That 0.5v was the MAX I saw in full sunlight.

[mmartell]

Re: Decorative Solar Lamp Question

Water getting in kills the interconnects or they bake in the sun and oxidize, and sometimes a cell can get cracked from hail. You likely have an open circuit.
I would load the (multimeter) with say a 1k resistor and in normal light measure the voltage output at various points in the array. There's cracks in the black plastic... which means water gets in.
It must be a series and parallel combination. I see 12 cells, and go with about 0.5VDC each, so maybe 3p4s? OOPS it's for a 4V SLA so likely all in series to give 6V..

I have no access to the solar array. There are only two wires coming out the bottom with what looks like hot glue sealing the hole.

The only interconnects are at the battery the rest are soldered to the small pcb.

[mmartell]

Re: Decorative Solar Lamp Question

Show a picture of the inside of the solar light and the back side of solar panel

The pic in the second post is the top of the unit and the bottom has two wires coming through from the panel.

There are also four small screws that must be securing the panel to the lid but I assumed it must also be glued in place to seal it off from the elements ?

[redwire]

Re: Decorative Solar Lamp Question

We'll need a pic of the backside. The solar array can be installed either on the top or the back side of the cover.
Either way, the solar array is pooched and it needs to come out if you want to repair it.
One cell on the middle far left has a rust spot- which is bad.

[mmartell]

Re: Decorative Solar Lamp Question

Removed the cover that houses the panel from the lid but now the panel still has to be removed from that somehow. Still working at it. Definitely evidence of water between those surfaces.

[eccerr0r]

Re: Decorative Solar Lamp Question

I have a solar panel (probably 4W) likewise having issues, it appears to simply be oxidation loss from either water or simply air leaks, pretty much total loss I think as they are glued sealed and cannot be serviced. Slightly bending (before anything else breaks) sometimes restores voltage...

I hope this is not the same fate of the 100W panels I have...which were actually supposed to be weather resistant, probably unlike that small panel.

[mmartell]

Re: Decorative Solar Lamp Question

I think mine are glued and sealed as well meaning it won't be possible to take them out without destroying them.

How much heat will these take from a hot air gun ?

[eccerr0r]

Re: Decorative Solar Lamp Question

I'm not sure how people came up with heat guns to deal with unsealing plastic, thermoset plastics (like epoxy) don't work that way. Even if it does release, it may become opaque and also made useless.

The larger panels I have at least are glass front, and are supposedly sealed together by pressure sensitive adhesives. But even so need to be heat resistant, after all, it has to be in the hot sun all day...

[redwire]

Re: Decorative Solar Lamp Question

Many small solar garden lamps are a square glass solar-array with hot glue underneath. One I put on a hot stove to soften the glue to pull the array out of the top plastic without melting that.

I'm still not sure how they put OP's solar lamp together. Looks like press-pins, I would gently pry around the edges and see. The only need to seal the clear cap, and the lid.
The problem is the plastics look near dead from UV and heat. Silicone caulk doesn't last long as a bodge. I would see what the cost of a new battery is and the $$ might not make the repair economical.

[mmartell]

Re: Decorative Solar Lamp Question

I'm not going to replace the battery. I would only like to use the solar panel itself and the led light source. Failing that I have no problem drilling holes in the top and using a few dollar store ones to make it function again at least until my wife sees what it looks like.

Thought I'd learn some stuff along the way too.

To that end I guess I should ask how possible it even is to repair non functioning panels ?

[sam_sam_sam]

Re: Decorative Solar Lamp Question

This can be done but not always successful

But you some how have to remove the outer cover

I would either to try to peal the outer cover off or just scrape the outer cover off of the connections and try to reconnect them together

I have done this before my self but ones fix the problem is to reseal it so it can be reused

[mmartell]

Re: Decorative Solar Lamp Question

So yes, this DOES look terrible. Several broken traces and oxidized solder pads as predicted.

Can the traces be replaced with wire ? And can I clean up the contacts with fresh solder or should they not be touched with an iron ?

[redwire]

Re: Decorative Solar Lamp Question

It looks fixable. I use q-tips with alcohol IPA to clean the corrosion and flux. I only resolder dull looking connections.

It's strange the long trace is black, not sure where the water got in (at the pad, then under the trace?) and what else got the electrolysis. Black is from current flowing through the water between two points.

If a pcb trace looks bad, then a thin jumper wire could be put in. Not sure if this board could sit lifted up a mm or so? Or does it need to be flat which is no more once you add wires.
The glue job is thick or thin in some places, really not a great job.