Coin cell battery charger

[Jay Kickliter] built his own coin cell battery recharger. This won’t work on the vast majority of coin cells as they are manufactured as disposable parts. But there are rechargeable options out there with model numbers that start with LR instead of CR. In this case he tailored the charging circuit around MCP73832 IC and chose components best suited for charging his 110 mAh LR2450. But we believe all of the LR options out there are rated for 3.6V so altering his design for use with different models should be a breeze.

We’ve been unhappy with the use of disposable coin cell batteries for some time. Sure, in a real-time clock where the cell might last 6-8 years this is not very wasteful. But in an Apple TV remote that gets a lot of use, we hate the choice of a disposable battery. All of our less-hip remotes which use AA or AAA have NiMH rechargeables in them and have used the same pair for year and years. So we’re happy to see this charger project come along.

Now the bad news. We looked around and indeed you can find LR2032; a rechargeable replacement for the CR2032. But the capacity rating falls way flat. The model we looked at boasts only 50 mAh while the disposable CR2032 offers something along the lines of 240 mAh. Hopefully this will change as battery tech evolves.

Shockingly fun quiz game

Gather your friends round the living room for a head-to-head quiz game. This one’s not quite as nice as you might think. Get an answer wrong and you’re going to get the Venkman treatment thanks to the stored electricity in a disposable camera flash circuit. [Israel] runs the game questions from a Windows machine, and uses a set of four USB joystick buzzers that let each contestant ring in. They all wear a cuff that houses electrodes for negative-reinforcement upon an incorrect answer. Since every contestant answers each question it won’t be long before you hear the uncomfortable yelp of failure from your guests. This seems a little bit more fair than shocking people for not calming their minds, but the video from that hack is still one of our all-time favorites.