Introduction: Cheap Solar Light Dismantled and Repurposed... Kind Off.

Picture of Cheap Solar Light Dismantled and Repurposed... Kind Off.

I got bored last weekend and bought a couple of cheap solar garden lights from the pound shop having taken them apart i then used some of the parts to make a small charger for my mp3 players aaa battery.
My apologies as this is an afterthought 'ible but its the thought that counts...

Step 1: Whats in the Box

Picture of Whats in the Box

In the box is very basic solar light with a very puny solar cell all sealed up in a fairly weather proof box.

I'm still thinking of ideas for the external box with just a little hot glue it would be weather proof enough. The stake and the post could also come in handy for the garden if i ever think of any thing....

Step 2: The Internals

Picture of The Internals

The internals fit inside the weather proof box..

This ones actually quite good for spares and parts. Some are much less useful coming with non standard battery sizes soldered directly to the control chip.

I had a look for a data sheet for the control chip but couldn't find it on the web I'll post up the part number later maybe some one could help out.

Its job is fairly simple when there is no current from the solar cell the chip starts discharging the battery to the led.

Step 3: More of the Gubbins

Picture of More of the Gubbins

In there you'll see a nimh battery, a handy AAA battery holder and a small joule thief type circuit on a pcb and a diode to stop the battery discharging back to panel in the dark.


The mini joule thief and the LED will come in handy for a torch in future.

Step 4: The Cell

Picture of The Cell

The solar cell that came with this unit is fairly weedy 2v job, i'm not sure what its current rating is but i'm very sure it won't be more than 30mah since these things tend to rely on not exceeding the c/10 charging rate that nimh batteries can handle with out worrying about over charging.

In order to charge a decent sized battery in less than a month i took a few of these lights ripped them apart and run the solar cells in parallel to up the charge rate.

Step 5: The Charger

Picture of The Charger

In order to charge a decent sized battery in less than a month i've put three cells in parallel which at the most will give about 90ma of charge current still under the 100ma that a 1000 mah battery can cope with.

To try and give this a modicum of water proofing i've chosen a sweets tin big enough to hold the the salvaged battery holder and three solar cells. Its a bit chunky to take out and about but it lives on my window sill charging so that doesn't really matter. Luckily my bedroom window is south facing so it gets the sun until about 5 am to about 5pm though for about an hour at mid day my irritating tree at the bottom of the garden cuts into my charging time.

I re-soldered the points on the cell with some cable out an older power supply and soldered the positive of the three cells to one of the diodes salvaged from the light then to the positive side of the battery box. Then the three negative leads were soldered to the negative point on the battery holder. Loaded the whole thing up with electrical tape to stop any shorts.

I considered a Schottky diode to decrease the voltage drop and thus increase the amount of time the device can charge as it would still work in more marginal conditions but i've got this diode from the light and i don't have any Schottky diodes to hand.

The first two cells i press out of the top of the unit but i managed to damage the cells in the proccess so for the third i just cut the top of the box plastic and all. I don't think there is too much loss of current from the damage.

A little bit of thick foamy double sided tape holds the cells well enough for this job.

Charger works well enough after a couple of days in full sunshine its enough to run my mp3 player for long enough to charge another battery.

This is more of a prototype to test if i got enough sun on my window sill on the out side of my house for a larger unit. I'll document that more thoroughly than this one.

Comments

cyberraxx (author)2011-10-14

Not a bad idea. I've bought quite a few of these from Pound World (about 7 now) and reused a couple for the parts. unlike yours mine have a 30mm x 40mm x 4mm dark solar panel. (forgotten type)

I've modified one so now the solar panel sits at 45 degrees and under the dome and the LED replaced with a string of 10 low-power LEDs (bought at Pound World) that were originally powered by 2 AAs. All have original batteries replaced with same brand NiMH batteries rated at 1000mAH (also bought at Pound World).

It actually lasts all night where as the un-modified ones only last a few hours. not sure why as all seem to use exactly the same identical parts, are identical in size and all get the same amount of sun light.

I'm wondering if I could somehow hook the PCBs in series and double the output. **gets out soldering iron.....**

blackdogg (author)2009-12-10

you can use parts of the control pannel to make a control panel for a levitator with electro magnet

slim_jim (author)2009-06-29

Didn't you spend an awful lot of money to come up with this funky recharger? For what you spent on three garden lights, you could have just purchased a real solar cell. Bigger, better, less ugly.

steveo_mcg (author)slim_jim2009-06-30

The lights were a pound each and i've re-purposed some of the other parts so while a better panel would have been not a lot more for £3 i've also got three tiny jule thiefs, 3 battery holders, 3aaa batteries and some other parts which i've yet to come up with a use for. If i had just purchased these for the cells your quite right a proper cell would have been (much) better but for the rest of the bits its not too bad. The charger was more of an afterthought.

mikedoth (author)2009-06-11

At the place I last rented we were going to throw out a bunch of these lights. I ended up taking them apart and keeping the boards in a box. I recently took them out and they had a bunch of resistors and transistors. Problem is I don't know how to test the transistors but they had some 1k ohm resistors which was very cool.

steveo_mcg (author)mikedoth2009-06-15

Yeah they're a good source of parts the old ones were much better though, these ones are so simple they only have a half dozen discrete parts.

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