Kipkay over at Metacafe has posted videos showing how you can take apart a 9V battery and use the cells as AAAA or AAA batteries (he has a similar trick for 12V -> 1.5V button batteries. I have played with batteries a lot in my life and never knew this. There was some speculation on reddit that it was a hoax of some kind, so as a good sciencer (like a scientist, but we don’t get the lab coats) who really didn’t want to get started on the morning chores, I decided to try it myself with a new 9V I had sitting around. I learned a couple useful things.
Duracell batteries are harder to open than the video implies. My dainty needle-nose pliers weren’t enough — I had to go find larger clampy ones. The edges of the case are also sharp. This would be very tricky to do in a car somewhere without tools.
He tells us these are AAAA cells, which makes sense. You know, I didn’t even know AAAA cells existed until I encountered a tablet stylus that used them. The handy thing is that they can double for AAA batteries in most cases — they just won’t last as long.
I decided to test them in my TI-86. One important thing he doesn’t mention is that there’s no reliable way to tell the polarity once you’ve disconnected them, so mark them somehow as you take them apart. If you’re just guessing, you’ve got 16 combinations to work through.
I didn’t think about this, so I cut them apart and folded over the remaining half-tabs on each end, then tested them all with a multimeter to get the polarity (my digital multimeter is missing, so I couldn’t get exact volt-readings).
I put them in the calculator. It didn’t turn on. I added a bit of aluminum foil at the contacts to make sure they were all touching.
It works!
So, in conclusion: This is a decent way to get AAA batteries in a pinch for a bit less than what they cost in the store, although I don’t use 9Vs for much, so situations where this is helpful are gonna be a bit rare. AAAs in a pack of 8 usually go for about $0.70 a battery, 9Vs for around $2 — so $0.33 per AAA. AAAA batteries are rare enough, and marked up enough, that if you have something that uses them this could be a worthwhile main source.
There are some really good points you made in your post…very insightful
This is great DIY project if you are bored
, i will try it myself later 
That’s pretty cool. Haven’s seen this before and I think I am gonna try it. Gonna go get a new battery right now.
Great hack. And good pictorial/guide. Many thanks for your insights and work.
Don’t be a dork! Buy the batteries you need and go on with your life. Save yourself, it’s too late for me.
Don’t be a dork!… LOL….:))
penyakit ginjal
If you look closely at the battery, you will see a indentation all the way around one end of the battery. This is a reliable way to find negative.
Where else can you find rechargeable AAAA batteries ! Great find folks.
Nice and detailed post dude. Also I think the positive terminal has a ring at the end which can remove ambiguity.
@Bilal: the negative end is actually the one with the ring around it.
@xkcd: thank you do much for this post. I’m out of AAAs at the moment and I needed to know if it was safe to take apart a Duracell. Thanks again!
-XPGiNfeCt