Batteries

A battery is an energy storage device in which the stored chemical energy is converted into electrical energy by reducing oxidation. In principle, these are two electrochemical substances (electrodes) with different electrochemical voltage potentials, which are housed in a housing with electrolyte (see figure 1).

In the case of an alkaline battery, the two electrodes consist of zinc (minus pole/anode) and manganese dioxide (plus pole/cathode). Concentrated caustic potash (potassium hydroxide) is used as electrolyte, with which the two electrodes and the separator are soaked (see figure 2).

Since batteries are intended for repeated use, they are also called primary cells. In contrast, rechargeable batteries are also referred to as secondary cells.
In colloquial language, however, the terms are often used incorrectly. Even experts speak of a car battery or starter battery, even though these energy donors are rechargeable lead-acid batteries.

Different chemistry results in different voltages

Since the different substances from which battery electrodes can be manufactured have different chemical voltage potentials, different nominal voltages are also produced for the respective battery types.

• 1.35 V for the mercury oxide zinc cell
• 1.5 V for the alkaline manganese cell
• 1.5 V for the zinc-carbon cell
• 1.4 V for the zinc-air cell
• 1.5 V for the lithium iron sulphide cell
• 1.55 V for the silver oxide zinc cell
• 2.9 to 3.7 V for lithium cells, depending on the cathode material

In the case of a 4.5 V flat battery or 9 V block battery, several individual cells are connected in series within the battery in order to maintain the higher voltage level.

For a 4.5 V flat battery, these are four cells (3 x 1.5 V = 4.5 V) and for a 9 V block battery, these are six cells (6 x 1.5 V = 9 V).

How does a battery work?

Battery test without aids

Practical advice 

As water is consumed when an alkaline battery is discharged, the battery "dries" internally. For AA batteries, a simple test can be used to check whether the battery is full or empty. The video above shows how to do it.

When the battery is full, the electrolyte is gel-like and thus attenuates the impact on the table top. Once the battery is discharged, the electrolyte is solid and the battery springs on the tabletop several times. Unfortunately, this trick only works with batteries of the size Mignon (AA).