Simple circuit to squeeze last drops of juice from batteries
The latest Weekend Projects video shows you how to build a "Joule Thief." Bre Pettis explains:
LinkWindell Oskay of Evil Mad Scientist Laboratories joins me to teach you how to make a super clever little circuit called the Joule Thief! The Joule Thief allows you to squeeze the life out of what most people think of as "dead" batteries!
We were inspired by Big Clive to make this project and it's the perfect platform for a flashlight, book reading light, or really just something you should make to get more use out of your batteries!
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Very amusing video! Of course, cats and kittens, always remember that P=VI, so if you up the V, you drop the I!
Cute.
But I think that using NiMH rechargeables would make more sense in general. The Rayovac Hybrid, Sanyo Eneloop and other "low-loss" models that will hold onto most of their charge for over a year are now widely available in department stores. And ANY type of NiMH made within the last 4 years will greatly outlast an alkaline in a camera anyway.
Adding some educational value to the video (like explaining how the circuit works) would have made it more worthwhile.
A few more things about NiMHs -
Get a charger that can handle "1 to 4" (with "1" being the important feature here) batteries at a time. You want one that charges each cell individually, which maximizes cell life AND your ability to use an odd number of cells necessary for particular devices. You don't want to be collecting spent batteries until you have the 2 or 4 needed to satisfy a stupidly designed charger.
Only mix cells of the same capacity within a device.
And don't leave spent cells on the shelf for weeks before recharging. Get them into a charger within a few days' time to prolong their useful life.
The low-loss cells I mentioned previously are suitable for things like wall clocks, remotes and other very low-drain devices. Just recharge them once per year.
Obviously this idea only really makes sense with non-rechargeable batteries, but I wonder if the same effect can be achieved with rechargeable ones as well. I wish the video hadn't just shown how to make this device, but also explained what it really does and how it works. Maybe one of the smart bb readers can answer this: Could it be that I'm observing a similar effect with NiMH batteries in my wireless mouse? My mouse uses pretty much every last bit of charge in my NiMHs, so that when I put them, after the mouse stopped working, into the charger in 'test' mode, the test light goes out within a second. But the thing is: After my mouse stopped working and the batteries are in this quasi-dead state, the mouse's LED will still continue to shine for a really long time. I'm thinking there might be a similar effect because my mouse apparently runs on 1.5 Volts (the batteries are wired up in parallel, when just one of them goes completely dead, you still get a grace period), but I really have no idea.
/me quits the early morning rambling and stumbles off to :make some coffee ;-)