This was fun maker-style project. I believe that if I was doing PEP
(which I am not because it's for a very different bioregion than the one I am in
) this would have qualified me for some Oddball points
Backstory: We are pretty rural. We have a tone of devices that charge via USB. Phones, e-readers, tablets, little lights, personal fans, all kinds of stuff. And the electrical grid is at least a little bit fragile; we get ice storms in in winter and pretty regular power outages during thunderstorm/tornado season.
One of our adaptations is that we've got a lot of those small "cell phone charger" auxiliary batteries. The kind that are the size of two packs of gum and hold enough juice to charge your phone a few times. They don't cost much, but they don't hold much juice, either. And the fun adventure (after you find one in the dark) is wondering whether it's got a charge in it. When was the last time I charged this thing? Was it in this calendar year?
One day, I got a notion. I've been standardized for close to a decade on the Black & Decker homeowner grade 18v rechargeable tools. They are almost completely obsolete now, but there was a huge line of yard tools and power tools that all used the same 18v lithium batteries, the ones about the size of 2/3 of a brick. Most of those lithium batteries have failed from age, and new ones used to cost $40 or so, so the tools go for cheap at garage sales with no-good batteries. Up until about a year ago, I was getting pretty short on working batteries, but I have a huge collection of the tools that I bought for $1, $2, and $3 over the years. Then some cheap Chinese nickle-metal hydride replacement batteries hit the market: about $20 with perhaps 30% more amp-hours of charge storage than the old lithiums had when new. So now I have plenty of the batteries again.
So what was my notion? I thought "Wouldn't it be nifty if I had a USB charger that plugged into those tool batteries? We'd be set for weeks on device charging, given how many of those batteries I have sitting around on smart chargers all the time."
First I went out and looked for a commercial product. No joy. Dewalt (I think) sells such a charger, but it's for a totally different (22v?) battery system. One or two outfits sell boom boxes (radio/cd players) styled like their tools that take the batteries and have USB outlets on them, but not Black & Decker that I could find.
Then I did a little research. I discovered that aftermarket USB charging sockets for cars (12v) are frequently designed to sell into the marine market (24v) also, so with a little looking, you can find a $5 charging socket that takes any voltage from 12 to 24. My tool/battery system is 18v -- perfect! The one I bought a few months ago
has doubled in price since I ordered mine; I suspect a derangement in the supply chain. (Lots of things on Amazon cost twice as much now as they did in January.) But I'll bet you can find a cheap one if you look.
So that was easy, but the other end is the clip that snaps onto the battery terminals. I could do it with alligator clips, but that's rinky-dink. I wanted a more elegant solution.
My "bright idea" was to salvage a battery clip from an existing Black & Decker tool. I've often bought them in lots -- a drill and a saw and a weed eater, say. When the whole pile comes with batteries (probably dead but one likes to check) and costs $5, I don't think too hard about how badly I need each tool in the collection. So I surveyed my inventory and found a leaf blower. WTF, a leaf blower? When am I gonna blow a leaf? I don't have any hard surfaces at my house that need cleaning, and leaves get to lie where they fall as mulch.
Seven screws later, the leaf blower fell apart in my hands. I had a battery clip to play with! And guess what? It used the same spade connectors as came on the USB charging socket. My wires are coded red and black for pos/neg, and the spades on the charging socket are marked pos/neg. Could it really be this easy?
No, not quite. The spades on the blower motor were soldered in place. One of my leads (red/positive) from the battery clip thus had to be cut off short so I could crimp on a new spade connection. (Two came with the USB charging socket.) But on the black/positive line, there was a tiny switch between the clip and the motor. That spade connector was not soldered, so I just unplugged it. Just like that, boom! I had a charger to charge USB devices from 18v Black & Decker tool batteries:
The spade connectors on the battery clip looked a little bit fragile, so I protected them with a bit of black electrical tape before plugging the battery clip onto a battery. Hey, look the LEDs on the USB charger socket are glowing!
Look at the pretty glowy lights on the front:
Then it was time to wrap the whole thing in black tape and test it with a "load". Happened to have an LED gooseneck light on my workbench so that became my USB test item. Hark, what light through yonder LED breaks?
It's a silly little project but I'm very pleased with it.