Battery Teardown To Get At The Cells Inside

Most of what people call batteries are actually cells. All of the common disposable alkaline batteries from AAA to D are single cells. The exception is the 9v battery which actually has six smaller cells inside of it. [Tom] took a look inside three different batteries to see what cells they’re hiding. Since he no longer uses the batteries for their intended purposes the individual cells may find a new life inside of one of his upcoming projects.

The six volt lantern battery on the left has four cells inside of it. This is no surprise since each zinc-carbon cell is rated for 1.5V. There’s not much that can be done with the internals since each cell is made of a carbon rod and zinc electrolyte ooze (rather than being sealed in their own packages).

Moving on to the rechargeable PP3 battery in the middle he finds the 8.4V unit is made up of seven 1.2V nickel-metal hydride cells. Many of them were shot, but we’d love to see one of the intact cells powering something small like a bristlebot.

The final component is an old laptop battery. Inside are an octet of Lithium Ion cells. The majority register 0V, but a few have 0.4V left on them. This is not surprising. We’ve seen power tool packs that have a few bad cells spoil the battery. It’s possible to resurrect a battery by combining good cells from two or more dead units.

40 thoughts on “Battery Teardown To Get At The Cells Inside

  1. The 6-volt cell surprised me. I remember taking apart a 6-volt cell which had 8 cells (2 groups of 4). Of course this was close to 10 years ago, so maybe the technology has changed or I’m remembering wrong.

  2. The six cells inside a decent 9V battery have a name; AAAA cells (think one smaller than an AAA battery.) I have cut open many 9 volts to get the cells out for flashlights that use a quadruple A battery. Note that really cheap Chinacorp 9 volts do not have cells inside, they have wax paper envelopes filled with goo instead.

  3. I have taken apart a couple 9v. The alkaline ones were 6 smaller AAAA cells, but lithium ones were a little different: they were 3 3v lithium cells, going horizontally across the battery, like this:

    | cell 1 |
    | cell 2 |
    | cell 3 |

  4. Be careful with the duracell 9V AAAA cells, they tend to easily explode (projectile their kathode) and spew their grey electrolyte (normally contained in the “sealed” 9V). You will find on many of your dead/depleted 9Vs there are bulges on the underside due to just this.

  5. I would urge anyone to not attempt to charge Li* cells recovered from old battery packs (well, any Li* cells really) if the voltage is under a couple of volts, even if they work fine the first time they may cause trouble later. Most likely is rapid self discharge and slow charge, but they may also overheat and burn.

    The usually mentioned minimum voltage is 2.5V, but the batteries should be ok to carefully charge if above 2.25V.

    Unloaded voltage under 2V? Trash!… Oh, sorry, i meant battery recycle bin.

    1. LiOn cylindrical cells have turned quite a few expensive aluminum LED flashlights into unexpected grenades. It is vitally important that all such cells in a battery maintain the same voltage. That’s why laptop batteries have circuits to monitor at least groups of 3 or 4 cells. If one cell gets weak, power from the others can make the weak one explode if there’s no sensing and protection system.

      1. It’s not really important that all cells have the same voltage, what’s actually important is that no cell gets completely discharged and starts charging backwards. You do not need a balance controller for this, but simply a protection chip on each cell, these can be had for less than a dollar each and can easily handle the maximum of a few amps from a laptop cell.

  6. I find the most useful part of a depleted 9V cell is the header, much stronger than those on pigtail. Savage the protection PCBs from old handphone batteries, and put in 2-S LiPo, and this lessen the pain when I forgot to turn off the portable.

    1. A warning, do not do this to industrial batteries with chlorine compounds, these compounds will release chlorine gas in dangerous quantities when opened.

      Almost all consumer batteries are “safe” though.

  7. All these batteries are homogeneous. I remember, many moons ago, seeing a radio (77 set) battery busted open. There were different types of cells withing the same battery. My memory of it is foggy but I believe it was a mix of AA and D; the thing was the size of a brick.

  8. “There’s not much that can be done with the internals since each cell is made of a carbon rod and zinc electrolyte ooze…”

    The carbon rods are actually quite useful. Great for performing water electrolysis, or other electrochemistry experiments. I’ve also used them to demonstrate how a carbon arc lamp works.

  9. I find that Duracell and Energiser 9V (PP3) batteries contain 6 AAAA cells, which are great for the most mini Maglite. The cheaper PP3 batteries seem to contain some dry pack thingy.

    With resurrecting laptop batteries by replacing cells, the hardest part will be to not upset the charge controller, there are a lot of safety regulation with these and they can be eager to brick themselves, possibly even blow some fuses.

  10. Just a side note: I’ve soldered the terminal end removed from a dead 9 volt battery to the output of a 9 volt wall wart.
    This allows a 9 volt device to be operated directly from the wall wart.

    (/pre-emptive) Yes, it is a hack! B^P

  11. Is it some US law that forces them to use cells? Or some EU law that forbids it? Since in europe they never seem to have such individual cells in 9 volt batteries, they are stacked chemical cells not individually packaged, and it seems odd companies would waste money on enclosing each cell when the end-user never is suppose to get at them.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.