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Solar charged drill made from trash!

Here is a short tutorial a wrote for a blog about one of many of my solar projects made from scavenged garbage. Any critiques or comments are welcome!

I’ll be the first to admit that while I love and own all types of unpowered tools, using them does take considerably longer and more effort than the powered ones (not surprisingly).

My background is that of a professional tinkerer, and a trained marine and environmental biologist. I have tinkered with electronics since I was a small child and while no expert (and welcome corrections (there is much I don’t understand)) what I know is from first hand tinkering and reading.

As a professional scavenger I have come to realize that we live in an incredibly wasteful and unsustainable society on many levels (no surprise to most readers I am sure). Over the years I have found drills, reciprocating saws, circular saws, chainsaws, and all types of other power tools thrown away for various reasons (all of which were easily fixed). You just have to keep your eyes open.

The project I am going to describe was one in which I took an older Black and Decker 7.2volt NiCad battery powered drill (I found in someones trash), and turned into a lithium ion solar charged drill for free. This project can be adapted to almost any brand, voltage, or type of battery powered tool.

Tools and supplies needed:


soldering iron



wire (decent gauge, larger than 3mm, preferably braided)

diode (at least rated for 20v)

some type of male/female plug with 2 leads

solar (PV) panels (5-10 volts (peak) more than the total battery volt.)

a battery powered tool of some sort

old lithium ion computer battery (non-mac)

This project assumes the reader has basic soldering knowledge and basic electrical knowledge, if not there are plenty of how-to’s and tutorials online.

Diodes can be scavenged from almost any types of old junk electronics whether it’s an old TV, old computer monitor, printer or many other types of “junk” electronics. Many diodes have numbers on them, just type it into the internet and you can usually find the power it is rated for. Unsolder it and you’re ready to go.

Same goes for scavenging male/female plugs, it can be the circular types used for plugging an AC adapter into electronics, the square type or anything really that you can plug together and has at least 2 leads. Adequate wires are easy to find in most electronics, just keep your eyes open.

Solar panels can be a little more difficult to find but with the massive influx of cheap solar junk from China if you know where to look they aren’t too hard. I got mine from the solar patio lights you see everywhere and only last about a year before they break. I am sure if walking around your neighborhood you’ll see some that no longer work, and offer to take them off your neighbors hands, or just look in the trash you’ll find some eventually. You can usually find adequate diodes in them as well. It is important to test your solar panels to make sure they function. Most patio light solar panels output around 4-5v or so at peak, but by linking them together in series (+ to -) the total is the sum of each panels voltage (e.g. 4v+4v=8v).

Now for the batteries. Most laptop computers made in the past 10 yrs use round lithium ion metal encased cells. The only exception I know of are Macs which use lithium ion polymer cells which don’t work so well in this application just because they are rectangular and flat. The large battery packs you see actually contain several smaller “cells” inside and when linked together (in series again) provide the voltage required, the same applies for power tools. When your battery no longer holds a charge it is usually because a single cell has “died” and no longer functions whereas the rest of the cells still function albeit at a lower efficiency then they did before. So you can disassemble an old laptop battery pack and test the cells with a multimeter. If all the cells show around 3.7v and one shows 0v you found your culprit.

Most cells are rated for 3.7v, so when deciding how many you will need for your project just make sure the sum is over the rating for your tool. In my case I needed at least 7.2v so I used 2 cells to power the drill (3.7v + 3.7v =7.4v). If you want your battery to last twice as long you can connect some of the batteries in parallel ( which produces sum of the current in milliamphours) (+ to + and – to –) but it is important to balance the batteries out. So if I wanted to double the run time of my drill I would have first made 2 sets of 2 cells together in series, (+ battery – to + battery –) then connect the sets together in parallel by connecting the positives on each end together and the negatives on each end together.

If this seems confusing read more about it online and get a solid grasp of the theory behind it before connecting batteries together causing a fire or worse an explosion.

The same goes for your solar panels wire them together to produce around 5-10 volts more than the sum of your batteries so that even when a cloud passes by you are still able to charge your batteries. For my project I wired 3 panels together in series (4+4+4=12v) and this works fine for me charging to 7.4v . Once again if you want to charge twice as fast just wire two sets of 3 panels (4+4+4=12v) together in parallel, and now you’re charging twice as fast.

Now in comes the diode. The diode functions as a one way valve, allowing electricity to travel in only one direction in your circuit. This is important because without it every time a cloud covers your panels, the electrons stored in your batteries will seep back out into the panels possibly damaging your panel and draining your battery. Diodes typically have a single white or black band indicating the orientation of it. The band indicates the negative side, so current flows from the banded side to the other, not vice-versa. The diode should be soldered between the + of your solar panels and the + of your batteries. If you have a multimeter you can set it to test your diode and make sure it is in the correct orientation, and working.

So let’s finally put everything together.

1. Determine some method to attach your batteries to the drill and that they will fit.

2. Determine if there are leads coming from the drill and which are + and – make sure they are long enough to reach the batteries.

3. Solder the drills + lead to the + side of the batteries as well as another wire to attach to the diode and male/female connector later.

4. Solder the – lead to the – side of the batteries as well as another wire to attach the male/female connector later.

5. Solder the diode banded side lead to the extra wire we soldered to the + side.

6. Solder one lead from the male/female connector to the non-banded side of the diode.

7. Solder the remaining – lead to the remaining lead of the male/female connector

8. Determine a way to mount the connector to the drill either drill a hole and glue it in or some other secure method.

9. Solder the other half of the male/female connector to your solar panels (making sure your orientation matches up to the other half attached to the batteries)

10. There are many ways to make this project look nicer and neater, some possibilities include encasing the back of your solar panels with fiberglass resin, to create a larger single panel, or using an old battery case (Dewalt etc) and taking out the old NiCad cells (please recycle, cadmium is deadly) and placing your new batteries, wires and diodes into the case, and closing it back up.

11. Remember this should be fun, educational, and there is always a way to build a better mousetrap. I always love to hear others ideas and criticisms. If you have the skills (and time) you could include a charge control system or other features.

A few tips

1. I always “soft wire” (aka. Twist the wires together) making sure none are touching and determine if my circuits work (like seeing if the drill works) before soldering things together.

2. Double check the orientation of your male/female connector using your voltmeter before plugging them together and possibly destroying your batteries.

3. Make sure that any and all bare wires or soldered joints are not exposed. I use electrical tape, hot glue, and heat shrink tubing to cover all bare surfaces. If you don’t when you shove it all together things well touch and short circuit.

The solar powered drill I made for free is still running strong after a year, and I’ve only had to recharge it once! Next solar project is a reciprocating saw!

Important note: Lithium ion batteries can explode (read the news headlines please). Make sure you know what you are doing before attempting this project. There is no charge controller in this simplified solar system so it is important to make sure not to over charge your batteries. I would monitor the voltage of your batteries the first time charging in full sun and determine the time it takes to reach full charge. That way you have idea about how long to keep it connected to the panels in the sun. Also note that the quality of the batteries you start with will largely determine how often it needs charged. So if your batteries are on their last legs expect the same from the drill.
projects like this could be surely interesting for regions with an economic crisis, where a lot of people with enough know how have no chance to get any jobs and have to rely on their own entrepreneurial spirit. and still there is a lot of waste around to get recycled in these regions, left overs from the time before the economic bubble burst...
Agreed, here where I live currently in Southern Louisiana, people why very low income have no concept of reuse or fixing things. Why this is certainly not uncommon in the rest of the US, it seems to me to be far worse down here.

I have found so many appliances, tools, tool boxes, and stuff I could go on all day about that it is crazy!
maybe this could be a matter of culture, sort of a 'use once and then throw away society', which on the other hand, would be a (little realized) chance for the ones that live in the shadows of our welfare.
some years ago i spent some time in cuba, and maybe it would make a nice anthropologic research, how people learned there to recycle things due to economic crisis and embargos. also they manage most complicated structures of black markets as a result of 'socialist' economy.
also in mumbay, india, i read about a whole favela (cant't remember the name now) specialized on recycling materials (of course they wanted to demolish the quater for some real estate speculation project...), which would be also a real treasure on the DIY and recycling know how.
I remember reading that Jeri Ellsworth who started CastAR a company that got 15 million in funding for a new type of immersive reality glasses got her interest in electronics as a kid. Her father was a auto mechanic who got her supplied with electronic part by simply asking customers to drop off dead electronics. Looking at how much the parts in some thing being thrown away would cost if bought separately there is a lot of wasted potential.
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