I stumbled across a semi-forgotten cat toy last week.  It’s one of their favorites — it’s a motion-sensitive ball that lights up in a variety of colors when kicked.  It also eats up batteries.  It takes three watch batteries, but I only had two left in the package in my desk drawer.  They were super-cheap on amazon ($5 for 30 including shipping, whereas Radio Shack will typically sell you a single battery for $2 or $3).  I ordered 30!  Good news!

The batteries arrived the other day.  I popped open the cat toy, went to insert three batteries, and discovered they’re too thick.  I got the wrong kind of battery.  Watch batteries of this kind are all the same voltage, but in a vast array of physical dimensions.  These had the right diameter, but were just too thick.  I’d accidentally ordered batteries for the kitchen timers — the only other things in the house that take watch batteries.  Bad news!

I looked closely at the design of the cat toy circuit board and battery holders.  If the batteries were too thin, I could have bent the tension tabs more for a tighter fit, but the batteries were too thick, so there was not much I could do that didn’t require surgery.  The battery holder design was pretty simple, though, so surgery was not completely out of the question.  I grabbed my trust Weller soldering iron and assorted other tools and hacked the battery holders.  Good news!

Additionally, now everything in the house that takes a watch battery (the kitchen timers and the cat toy) all take the same battery!  There’s no need to stock two different kinds.  Good news!

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I stumbled across a semi-forgotten cat toy last week.  It’s one of their favorites — it’s a motion-sensitive ball that lights up in a variety of colors when kicked.  It...