Well, I built this yesterday in response to my DLO remote for my iPod docking station going dead. After opening the battery compartment, I discovered that the power source for the remote was a small lithium button cell that put out 3 volts. I went over to the corner Walgreens and was flabbergasted to learn that one of those little button batteries cost $4.29! Why, that's nearly 2.7% of the cost of the docking station when I bought it new. I simply was not going to fall prey to the rampant highway robbery of purchasing a small power cell for my remote.In formulating a strategy for replacing the remote's power supply, I set some criteria for getting the remote functioning once again:
The solution had to be less than the cost of a new battery.
The remote must be fully functional.
The power source must last as long or significantly longer than the 3V lithium replacement battery.
Must be friendly to the environment.
Ancillary problems to be solved:
Must be able to find the remote.
Solution must make the remote far more interesting than before.
To get the poor dead remote functional once again was simple: provide a power source of 3 volts or close. Obviously the amperage requirement of the device was very low given the size of the battery that normally powers the device. Making the device power source last longer than the button cell was simple; just make the capacity bigger. Batteries of this size normally deliver several micro-amp hours of current. I wanted to go completely overboard and provide at least several hours of current at several tenths, a whole amp hour if I could manage it. This would require a power cell significantly larger than the nominal power cell. My mind was reeling with the possibilities.
To satisfy the environmentally friendly aspect of the project, I decided to try to build a battery out of components I had lying around, or could buy at the local Dollar Store, keeping in mind the$4.29 limit. It turns out that rummaging through some boxes in my closet provided everything I needed to bring my concept to reality:
Two baby food jars that I was using to store miscellaneous small parts.
Two large hose clamps.
Two nearly dead D-cell batteries.
A brand new package of 2 part epoxy.
Black and red wire, 22 gauge.
In the kitchen I found sea salt and the tap provided a source of water.
I stripped the dead batteries of their steel casings so I could get to the zinc casing that acts as the anode for the cell. I cleaned the casings with some sandpaper to ready them for soldering. My next step was to use my Greenlee punch to make an aperture in the baby food jar lid large enough to accommodate the D-cell. About a centimeter down from the top of the cell, I soldered the cell to the lid around the entire circumference, making sure that I wasn't leaving any voids where electrolyte could leak through. To make sure that no electrolyte leaked through the nylon insulator at the top between the positive cathode and negative anode, I sealed it with a liberal coating of 3-minute epoxy. Since the EMF of a carbon-zinc chloride cell was about 1.4 volts, I would need two cells wired in series to satisfy the voltage requirements of the remote. My next step after soldering the two primary cells to their jar lids was to make a couple of small holes in each to allow the flow of aqueous electrolyte into the cell.
Making the new electrolyte was simple. I just need to make a saturated sodium chloride solution. I mixed the sea salt with water from the tap. No complex chemistry here and it was completely safe to make. I aliquoted enough of the saltwater into each jar to reach the holes I drilled in the dead D-cells. To ensure that nothing leaks out, I sealed the lid to the jar with more epoxy.Now to make sure that these two cells stayed together as a pair, I used the two large hose clamps. Since one alone was too small to reach around both cells, I fed the ends of the clamps into the other to make one big clamp with two tightening screws, making the cell pair look that much more robust. After the epoxy set, I was ready to connect them in series. Soldering a wire from the cathode of one cell to the anode of the other cell and a wire to the battery's anode and cathode made the battery functional and ready to hook up to the remote. I opened the remote up, identified the positive and negative terminals and soldered the wires from my newly-built battery. I left the old battery cover off to provide an entry for the substantially larger wires to get through and I was nearly done. The hose clamps made a nice surface to attach the remote to the battery with heavy duty double sided tape.
The new power source has an EMF of about 2.8 volts; plenty enough to run the remote and will last substantially longer than the little lithium cell. The little lithium cell had about 225 mAh capacity and weighed in at 0.1 ounce or 3 grams, this bad boy has about 16000 mAh capacity and weighs in at over a pound and a half or 700 grams. The ancillary project goal of making the remote loss proof was achieved as it seems highly unlikely that this combo will be lost inside the couch between the cushions. It also gives the remote a new aesthetic that appeals to me - and maybe only me. At least I didn't pay $4.29 for a battery, and I got to distract myself for a couple of hours.
