Commercially working batteries had become widely used after their invention in the early 19th century, but they had many drawbacks. The electrolyte was a liquid acid which meant the casing was usually glass, making them relatively delicate, heavy and hazardous if they broke or spilled.
They were robust enough to work on fairly stable platforms such as rail wagons, but generally needed a static location.
In 1886, Carl Gassner made a breakthrough and patented the zinc-carbon dry cell. This chemistry allowed the liquid electrolyte to be mixed with a gelling agent (originally plaster of Paris) to make a paste. It wasn’t truly dry, but enough for the battery to be able to operate at any angle for any length of time.
Furthermore, it could be made small enough to fit in the hand and so opened the door to truly portable appliances such as flashlights and portable radios. It would dominate the domestic battery market for nearly half a century.
Note, some sources and manufacturers refer to zinc-carbon as the Leclanché cell, because the basic idea of using zinc and carbon really belongs to Georges Leclanché who patented the design in 1866. Carl Gassner just figured out how to make the electrolyte a paste, rather than a spill-able liquid.
Basic structure of a zinc-carbon battery
The elements are as follows:
- An anode (negative) – zinc metal often forming the battery case and negative terminal.
- A cathode (positive) – a carbon rod in the center of the battery, surrounded by manganese dioxide and connected to the positive terminal.
- A separator – often simply starch coated paper.
- Electrolyte – ammonium chloride paste.
- A gasket to separate the positive terminal from the negatively charged case.
In some models the zinc metal case is covered by a plastic shell. This is because it is very close to the positive terminal at the top end of the battery and accidental shorting when placed in a metal container or next to other batteries is possible.
Zinc-carbon and zinc-chloride
As technology progressed and manufacturing processes were refined, it was possible to use purer zinc and manganese, which led to the zinc-chloride version of the battery. These last up to four times longer than the basic zinc-carbon battery and offer a steadier voltage during discharge.
They are usually marked by manufacturers as heavy-duty, extra-heavy-duty, or super-heavy-duty. Both zinc-carbon and zinc-chloride batteries remain in production to this day. For more on the difference between the two see Zinc-carbon versus zinc-chloride.
Zinc based battery sizes
The most commonly seen zinc based batteries are now zinc-chloride (just look for the ‘heavy duty’ branding), but from time to time you may spot an original zinc-carbon. They are usually offered in the following sizes:
- Lantern (spring and screw terminals)
Zinc-carbon versus other chemistries
Despite many new technologies appearing on the market since its invention, zinc-carbon remains in use because of its exceptionally low production costs. As such, it is the battery of choice for electronic device manufacturers who like to say “Batteries Included” and the one that ultra cheap retailers stock.
Its other virtue is a very low rate of self-discharge, making it ideal for applications which are used from time to time. Such as remote controls and smoke alarms.
In reality however, Alkaline based batteries offer better value for money in every other respect, lasting up to 10 times longer for only a little extra cost. Lithium-metal options are also superior, operating at wider temperature extremes and giving a cell voltage over twice that of zinc based units.
Zinc-carbon are also the most likely of all chemistries to leak due to their construction, where the case itself forms the anode (negative). During the discharge process, this zinc container is literally consumed and if it becomes too thin, holes can form. Zinc-chloride batteries are slightly tougher in this respect but still more likely to corrode and leak than alkaline or lithium.