It says it right on the side of every alkaline battery – do not attempt to recharge. By which of course the manufacturer means don’t try to force electrons back into the cell. But [Cody] figured he could work around that safety warning chemically, by replacing the guts of an alkaline dry cell.
The batteries in question were certainly old, gnarly looking, and pretty dead – [Cody] barely got a reading on his multimeter. As you can see after the break, he cleaned off the exterior corrosion and did a quick teardown of the dry cells, removing the remains of the zinc anode, now in the form of zinc oxide paste looking very much like what you’d slather on your nose before a day at the beach. He filled the resulting cavity with a putty of zinc dust, freshened up the electrolyte charge with a squirt of 20% potassium hydroxide, sealed up the cell with a little silicone caulking, and put the recycled cell to the test. Result: 1.27 volts. Not too shabby.
[Cody] remarked that he “probably did something wrong” since he wasn’t getting the full 1.5 volts out of his cell; we suspect that since he only renewed the zinc anode and left the manganese oxide cathode alone, he’s only getting the juice out of the half reaction of the zinc side of the electrochemical equation, which has a potential of 1.28V.
A neat hack, to be sure, but it couldn’t possibly make economic sense, right? Not so fast. The zinc dust he used goes for about $30USD a pound, and KOH is about that price for either a 5 pound bucket or a one gallon jug of 45% solution. That would renew the anodes of a LOT of D-sized cells. Even if you added in another $30USD for 500g of manganese oxide, you might still come out ahead of the game. Either way, it’s a good hack to file away if you ever need to MacGyver your way out of a bind.
If you haven’t had enough of the insides of batteries, we’ve looked at tear-downs to get at the dry cells inside. We’ve also discussed the alkaline battery bounce test. And [Cody] has some other useful non-battery tips that we’ve covered before, like his urine-fueled anti-Gorn gunpowder.