What's inside a PP3 battery, and why? The PP3, also known as a 6F22, 9 volt, or transistor battery, looks like this on the outside:
This is the zinc chloride type of PP3 volt battery. There is also an alkaline type which looks different inside.
Let's strip off the metal jacket and see what's inside.
The red wire seems to join the positive (+) terminal to the bottom of the battery. The negative terminal (-) has no visible connection yet. Let's lift up that connector plate and see what's underneath.
Now we can see that the negative terminal is soldered to a metal plate on top of the battery. What does the bottom of the battery look like?
The red wire is soldered to a similar metal plate at the bottom of the battery. The battery seems to consist of a stack of six cells wrapped in a plastic sleeve. Let's strip off the sleeve, cut off the yellow paper band and see if we can take the stack apart.
Under the plastic sleeve, the stack of cells is coated in wax. This is probably to stop the chemicals inside them from drying out. The cells can easily be prised apart. Here's a closer look at one of the cells, first in its original state and then with the wax cleaned off. Each cell is a little zinc-carbon galvanic cell that produces 1.60 volts.
Now it's time to look at one cell in more detail. It has a plastic sleeve around it, so let's take that off for a start.
Now, on the left, we can see a cake of some pasty electrolyte in a paper cup. Turning it upside-down shows that the paper cup rests on a metal plate. Let's separate the cup from the metal plate. Here's what it looks like.
There's nothing left to take apart now, so I'm going to stack up all the cells and see if it still works. If one cell gives 1.60 volts, then I should get 9.6 volts out of the stack.
Yes, that worked, with even more volts than I expected, and with the metal jacket back on it looks as good as new! Now where did I put that receipt?