Batteries: a closer look

Accumulators, or rechargeable batteries, or secondary batteries (generally called batteries), are electro-chemical systems able to accumulate an electrical energy to be released back according to the electrical demand. They are made of elementary cells, electrically connected one to the others in series or in parallel, to reach the requested voltage (Volt) and current (Ampere) values.

The specific values of a battery, for ex. a car battery starter, are:

Nominal tension: expressed in Volt consists of the average electrical cell output passing from the positive to the negative pole. It is a marker of the warning level linked to the electrical energy: tensions above 60 V are dangerous for the human body. For this reason, the use of electrical devices is to be made with special care.

Nominal capacity: shown in Ah it represents, in a simplified way, the number of Ampere that a battery can release for one hour continuously.

Maximum release: shown in Ampere it represents the maximum current the battery can release for few seconds (for example to start a car engine).

Applied technology: shown withacronyms like Pb, Li, etc.

Geometrical measures: they are important when the compartment, as inside a car, has a limited size

When a single battery does not have the requested characteristics for its application, it is necessary to assembly more batteries together. The contemporary use of more batteries is made with a series or a parallel setting.

By connecting the elements properly, it is possible to build battery packages suitable for a wide series of applications, from the low power and low capacity ones for medical use or for consumer electronics, up to a high power and high capacity for electrical and hybrid vehicles. Even the bigger batteries can be connected in series and in parallel.

By connecting the elements in series (positive with negative) the tension arises. Total tension is the sum of each element tension. In the picture example the total tension of two 12V batteries connected in series is 24 V.

Series Connection

By connecting the elements in parallel (positive with negative) the capacity arises. The total capacity is the sum of each element capacity. In the example of the picture above the total capacity of two batteries of 200 Ah connected in parallel is 400 Ah.

By combining the two methods it is possible to obtain all the tensions and capacity combinations.

The elements in the picture hereunder are horizontally connected in series.

The two packs that result are (vertically) connected in parallel.

Parallel Connection

Series – Parallel Connection