To think of a solution, first you need to find a problem!
Now, due to the limitations of regular rechargeables, I still use disposable alkaline batteries in a few places in my house in devices like flashlights, my wireless keyboard, remotes, clocks and a "emergency" back ups for when a rechargeable died and I didn't want to wait for them.
As you can see, most of those devices have a fairly low to extremely low battery "turn over" rate and hence my "stock" of alkaline batteries is very small and I often have none or run out when I need some fresh ones.
Problematic no? Yes! Not to mention expensive and hard on the environment!
Well I have long known about these special chargers for regular alkaline batteries that could "top off" a normal, non-rechargeable battery and give you some more use from an otherwise "dead" disposable battery. The problem was I didn't want to buy yet ANOTHER charger to go with the stack I already have for Renewals, just NiCad's, just NiMH's and of course NiCd AND NiMH's...
No joke, I have 11 battery chargers in my house. So, another one was NOT welcome.
Still, I was curious about the concept and spent some time poking through the internet for tidbits on the interesting idea of doing something that was not supposed to be possible, or even attempted according to the warnings on disposable batteries...
There is surprisingly little solid information about the whole concept, but I mostly found that it could be done and done fairly safely if you followed some basic rules, used a custom built charger and baby sat it... Oh goody! I won't need to buy another charger, I LOVE building electronics AND I can use one of these old useless renewal chargers for parts! Whee!
Wait... I'm going to build a charger to recharge alkalines... I HAVE a charger designed to charge rechargeable ALKALINES... What the heck is the difference?
Turns out, not that much.
About half an hour of research on Google, Rayovac.com and Wikipedia, left my lazy side grinning like an idiot. Between rechargeable alkalines and disposable alkalines, there were minor differences in chemistry so the rechargeable variation would take a charge better and repeatedly, along with better leak protection... In short WHAT difference?
I grabbed my tools and I found, to my delight, that the Renewal charger uses a low average current (~20-40ma) provided by 2 volt pulse at a 50% duty cycle... According to the information I've found that's practically PERFECT for charging a regular alkaline! It's even got a "full charge" cut off at 1.7 volts, a bit high, but I wouldn't even need to baby sit it when it was charging! Besides, if a battery blew up, no big deal, I had 3 more and the charger was useless anyhow!
I could Reduce, Reuse AND Recycle all at once! At this point I was happy enough to start crapping electrons.
Figuring I should be able to stuff a regular alkaline right into a Renewal charger and be good to go, I grabbed a near death battery from my remote control and popped it in to witness the astonishing act of... nothing.
Back to my tools and a closer examination. Turns out the battery wasn't making a connection because Rayovac designed a safety system so people couldn't do exactly what I was trying. (ref: http://www.rayovac.com/technical/wp_batoptions.htm
-Near the bottom above Fig. 6 after lots of marketing propaganda and useless fluff)
Now, if there is one thing I have learned in life (often after regaining consciousness) the best part about safeties, is finding ways to get around them ;)
Lets get crackin'!