A while back, I had some fun pulling apart an old carbon-zinc style 9V cell, which is a pretty basic experiment I think everyone should at least try at some stage in their lives. This time, it’s time to teardown some alkaline versions, which are built differently for the most part.
Since we do use up a few 9V cells around the place, I’ve made it a habit to shop at element14, and buy “trade” branded batteries in bulk, whichever is on special at the given time. As a result of the last two batches of purchases, I’ve ended up with a Duracell Procell and a new style Energizer Industrial cell, which are both depleted and are going to hit the bin anyway.
You might not have heard of these brands, but they are the “trade” bulk versions of the batteries you might find in your supermarket. It ends up being potentially cheaper, but you are told that you get virtually the same quality. These are normally intended for companies to integrate into their products as the “included” batteries, or by tradesmen doing things like bulk smoke detector battery replacement. The difference in branding is mainly to try and avoid cannibalizing the profits from their retail packaged blister packs, hence the markings on the cell outer jacket of “Not for Retail Trade”.
The Duracell Procell has a metal outer jacket and is Made in the USA – quite a nice quality feeling cell. The Energizer Industrial cell has a plastic label outer over a plastic body, which seems common for “newer” cost-reduced cells, and is Made in China.
Teardown: Duracell Procell
We start the teardowns with the Duracell Procell. For those following at home, feel free to try this – you need a good set of needle-nose pliers and possibly a flat head screwdriver and start prying at the seam where the can joins together.
Once you have lifted the crimp, you should be able to separate the ends and “unwrap” the cell.
This cell seems to have an interesting construction where the inner set of six AAAA flat-ended cells are shrink wrapped together into an assembly. Despite this, the empty cell (that is the weakest in the pack) seems to have leaked causing some corrosion on the inside of the can.
As the whole pack is shrink wrapped, it comes out of the can neatly in a bundle. The top contacts are spot-welded to tabs which lead into the pack. Using a sharp knife, we can cut away the outer heatshrink and take a look at the pack construction.
As it turns out, there are cardboard/paper insulators at each end, and the cells are individually tabbed and spot welded together to form the battery. This ensures good reliable contacts, and is a construction technique used to produce serious battery packs, such as the rechargeable batteries in your laptop. I didn’t expect to see this in a disposable battery.
Each of the cells has a printed code on it, and is individually shrink-wrapped in a semi-transparent yellow coloured plastic.
That’s a lot of material for a disposable battery, as the active material is contained inside these individual AAAA cells. Some of the material does “get out” and cause corrosion, but because of the outer can, your device is “protected” against leakage to some extent.
Teardown: Energizer Industrial
The construction of the Energizer Industrial cell is a little different, and it has a plastic body. Tearing this apart involves first picking at the end of the outer wrapping label, and then using a sharp knife or screwdriver, prying at the seam at the top where the battery contact panel has been glued to the rest of the “tub”.
Once you have gained entry, the top contact panel will come off and reveal a white insulating piece of glossy card. The contacts are, similarly to the Procell, spot welded to tabs. Amazing. In this case, there is a fluorescent orange stripe, which is probably a factory marking.
There’s really not much to do but “lift up” and pull the whole assembly out of the tub. Then you are greeted by, again, six AAAA cells which are all individually label-wrapped in silver and black marked wrapping. This is very much reminiscent of the Energizer colouration scheme. A batch code is visible on the cell itself.
Not unlike the Procell, this too used spot-weld construction. Maybe it’s not a big deal anymore …
Of course, here is the cells all turned out into a loop …
Teardown Bonus: Aldi Activ Energy
It just so happened that there was a small battery recycling box at the university where there were a few disposed batteries, and a friend was well equipped with some tools and didn’t mind me rifling through some of the batteries and tearing them apart. Unfortunately, I didn’t have my photography gear, so these are all lower-quality phone-camera shots.
The first bonus teardown cell is a retail cell sold by the discount supermarket chain, Aldi. They brand their cells “Activ Energy” and claim them to be “just as good” as the leading brand (i.e. Energizer).
This is where there is a nice surprise. The cell was a plastic construction – tearing the wrap off of the cell and getting out some scissors to pry off the top … gee, that looks somewhat familiar …
Indeed, this is pretty much the same as the Energizer Industrial cell. It looks the same with the cardboard separator and silver/black adhesive wrap on the cells.
The separator had a fluorescent stripe on it as well, although it was a light green rather than an orange one. The cells also had batch codes.
There seem to also be green dot markings placed on the cells. So maybe indeed the Aldi 9V cell is “as good” as the major brands because it is manufactured by the same factories in China as the leading brand. However, without further testing, we cannot be sure that the cells used as of the same standard, but physically they share significant similarities.
Teardown Bonus: Energizer Retail
Now we get to another interesting conundrum – while the Energizer Industrial cells are in plastic cases, the retail batteries are almost always in metal cans. This suggests the batteries are actually materially different. One candidate cell picked out from the recycling bin had identical expiry date to the Industrial cell, which indicates they are similar manufacturing vintage, but had a completely different construction.
This construction resembles the lozenge format more commonly seen in the carbon-zinc style batteries, but is very neat. It doesn’t feature haphazard cellophane like the carbon-zinc does, and instead, has hard plastic framed lozenge shaped cells sticky-taped together into a stack, which probably explains the “divot” on the contact surface.
This type of construction is something I’ve never seen before in an alkaline cell.
Teardown Bonus: Eveready Gold
I can remember a long time ago when there were television commercials for this branding, pitching it as the better “value” alternative to other alkalines, without saying that they come from the same parent company as Energizer. In essence, they were just competing with themselves.
The construction on this battery is much closer to what I remembered an alkaline 9V cell would be. Just a loose assortment of clear-shrink-wrapped AAAA cells, with foil-on-cardboard ends “pressed up” by a pressure contact to the cell ends to make the contact. The pressure was supplied by the crimped outer metal jacket plus the stiff end-boards. Despite this arrangement, the cells were generally reliable and contact wasn’t much of an issue.
However, the pressure also “held together” the thin end-walls of the cell, which may have been thinned to reduce metal usage, weight and also allow for internal cell pressure to help “push against” the foil contacts. This did lead to an outgassing (hissing) from several cells, as the battery was opened and the pressure holding the ends down was “released”. Do be careful!
There are many ways to build a 9V alkaline battery, many of them involving AAAA sized cells, but not all of them. It seems more recent cells have been using more spot-welding techniques for more reliable contacts, which may or may not increase construction complexity and cost. However, there was a surprise in the Aldi cell being very similar to the Energizer Industrial cell, and the Energizer Retail cell being made using a technique resembling the carbon zinc style batteries. You see something new everyday!