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.
Ted…
Are you sure this is correct?…
Additionally there is an easy way to discern the positive versus negative ends of a battery.
Are you ready for this?
…are you?
A diode. For the sake of simplicity a LED (and a 1K resistor…you know, so you don’t blow out the LED). Since current can only travel in one direction through a diode (through a process leading sciencers have determined to be magic) the light will only turn on when you have the battery connected correctly. (And it has a low enough power requirement that you can test individual batteries thus eliminating the exponential combination problem.
HAHA. I love the test screen. e^x-x
19.9990999792
*siren goes off*
ROUNDING ERROR!! EVERYONE EVACUATE!!
You renew my hope to find an IC packed with tiny vacuum tubes.
I tried it and it exploded in my hand
Nifty. Forwarding this to a preparedness site I frequent.
Hey, thanks for this. A few people come into my store asking for AAAA batteries. Now I have an answer for them!
I had great fun trying to rip apart a 9v Energiser ™ branded battery. But following some cut fingers, I managed to mangle the case open and get to the cells inside. Interestingly, its quite easy to tell the poles apart because the +ve end has a small bump.
I still can’t get it to work… I tell you though, I nearly split my finger open on the battery case. Not for the clumsy I’d say. Interesting idea, thanks.
Great stuff! It worked, eventually. Hey derek, you’re right not for the clumsy
what exactly was the problem? maybe we can help?
Gord
Yeah, a hoax indeed
http://www.snopes.com/photos/humor/batteryhack.asp
Randall, your dainty needlenose are fine for this. Pry a corner of the Duracell’s seam with a knife and then use the pliers like a sardine tin key. I just did it to retrieve the 9v button-snaps for a project. Like most things, it’s about finding the archimedes spot.
Great! Thanks for your trying. You took away a lot of questions!
Cheap Paintball Guns…
I found your site on technorati and read a few of your other posts. Keep up the good work. I just added your RSS feed to my Google News Reader. Looking forward to reading more from you….
Well, maybe a short video showing the detail would be good for those of us who are not so articulate at these DIY things…. any more cool ideas?
[...] [...]
[...] 9V batteries are just 6 AAAAs in series. (That said, cut batteries open at your own risk!) [...]
@Mrten, “This works only with the ‘alkaline’ kind of 9V batteries, others are, as commented above, stacked.”
Really? My opened _alkaline_ ANSMANN 9V is stacked.
Also, nobody knows AAAA. Even battery companies misspell it! Finding AAAA: both difficult and expensive. Wikipedia has some model numbers.
The wonderful idea! Great stuff!
Congratulations!
I too discovered this a few years back when need AAAA’s for a laser pointer, saves a fortune when taken from 9V as opposed to a package of 4A. huge markup thanks for the reminder of this usefully Idea.
[...] you can get AAAAs anywhere you can buy name-brand 9V batteries, since a 9V is usually powered by six AAAA batteries wired in series (this trick also works with rechargeable [...]
Just saw that this got referenced in this month’s IEEE Spectrum magazine! (IEEE = Institute for Electrical and Electronics Engineers, kind of a big deal)
Between the increasing commonality of this sort of reference and the You Tube type altering of reality, XKCD certainly is becoming part of Mainstream Internet Geek Culture.
Linkage, per previous comment: http://spectrum.ieee.org/nov08/6916/6
thanks
Really usefull battery experience. some useful battery tips at: http://www.cheap-laptop-battery.co.uk
I just found out that the hack doesn’t work on Radioshack 9V batteries… they don’t have individual cells inside, just a sealed transparent plastic case with 6 “layers” of some sort inside. Just wasted a perfectly good battery and still need a AAAA for my bluetooth headset. :-(
hello!!!:)
your website sucks batterys shouldnt be invented everything should be charged like the nintendo ds
I was just browsing on Google for things to do with a 9v battery. I also saw a video on how to hack a 12v battery(i thinks its AA). The 12v batterys have eight of the small, flat, super expensive battery cells in them