DIY: The SunCat Solar Rechargeable Battery

17 by Doug Gunzelmann on February 17, 2009

Knut Karlsen constructed his very own solar rechargeable batteries that can sit out in the light and convert the suns rays into stored power. He has documented this DIY project to create the prototype SunCat battery.

“The batteries should just bask in the sun like a cat and left for a while, in a sunny window, they would slowly recharge.”

Solar charges meant to juice up your battery powered gadgets, like the Solio, have been on the market for years. Turns out Knut has some connections at the Institute for Energy Technology or IFE (very convenient contacts!) where he was able to procure some flexible solar cells. This may be a slight hiccup in materials for a quick DIY home project but never the less flexible solar cells, or Photo Voltaics, are on the market in all sorts of shapes, sizes, and prices.

Knut attached the solar cells (which were already the correct dimensions) to old rechargeable NiMH batteries. The cells are rated at 1.8V and the batteries at 1.5V, which is acceptable.

Next, he used contacts from an old camera to connect the negative pole to the photo voltaic cells with the help of a conductive silver pen to finish the connection.

This type of charging arrangement is called a trickle charger and works by slowly charging the battery. They can be left charging in this way indefinately without over loading the battery. However, this is the slowest form of charging a battery.

Sources: Bare Knut Blog

Bart Mitchell

Very slick idea. He should market reusable sleeves. I bet he would make a killing.
z

lll
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MRme

interesting idea but what are you doing to keep from overcharging and killing the battery
Doug

@ MRME

“This type of charging arrangement is called a trickle charger and works by slowly charging the battery. They can be left charging in this way indefinately without over loading the battery. However, this is the slowest form of charging a battery.”
Uncle B

A new product, soon to come manufactured in China,cheap enough for all to enjoy, complete with circuitry to prevent over-charge! Love it, batteries we never have to throw away! It will kill the disposable battery makers and may help us get off grid, a good thing, as the (GRD) great republican depression tightens our belts, and cuts down on our disposable incomes. We need more survival items like this to ensure some quality in our lives as the neo-cons, bankers, swindlers, shylocks and shysters have their way with our money. Good, renewable stuff, just love Solar energy!
Andrew

But wouldn’t leaving the batteries out in the sun make them hot and likely to explode?
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Live

so wat do u need to make it…?
i’m doing a project on it….
i think it doesn’t say….
http://emachinesamepagerdoluan80@yahoo.com Luan Do ( deaf )

Type your comment here…
http://venetianblinds.blogbank.pl/ Glinda Fergusson

Thanks for this post, it certainly helped me in terms of how I can improve things. Speaking of improving, a good way to clean any type of window blind is to make use of a can of compressed air, or maybe a pet hair roller.
Carlos

I really like the concept. However, I think it might be inefficient. After all, no matter how you position your batteries, there will always be some part of the solar panel that doesn’t get direct sunlight.
Belle

Hello,I have a question. So, after charging are you supposed to remove the solar cells? Or just leave it there?
Belle

Another question, what material was it that you used for connecting the negative and positive poles to the solar cells? Is that copper or aluminum? Because it’s quite expensive to tear apart a DSLR.

JL

To answer the questions posed…
1) the batteries will never overcharge – solar cell wraps only provide a trickle of current – they may take a long time… uh, they WILL take a longer time than in any charger! – to recharge, but they won’t ever overcharge, even as-built. They also don’t need to be very efficient, as any sun on part of the surface will provide the right voltage at a trickle current rate sufficient to recharge the battery, even if half or more is shaded.

2) they won’t heat up enough in the sun to be a problem, but you can move them into the shade for a few minutes before using them if they do get warm.

3) you can leave the solar cell sleeves on forever, or switch them to new batteries when the old ones no longer take a charge. They are “wired” using simple copper foil and conducting paste pen traces, not soldering (!), so changing them over is easy enough. That copper foil also comes on rolls for “leading” stained glass, it has an adhesive on one side, but you can use the uncoated side for conducting electricity – I do! (No need to strip a DSLR!) These batteries are designed for projects and are slightly smaller than what we buy in the store, so they have no covering; all you need to complete them is the solar cell wrap (I don’t have a source, sorry), some copper foil traces (see above), conductive paste (comes in “pen” form), and adhesive to hole the solar cell wraps on – possibly a good clear tape would work too.

Excellent idea, great project – I might have to try it myself – I use a lot of rechargeables!!