Battery or accumulator – what is the difference?

Batteries (more precisely primary batteries) cannot be recharged – they have accumulated energy for a single use. The electrochemical reaction that takes place in them is irreversible. The main part of a battery is the primary cell.

The most common are AAA, AA batteries, etc., as we know them from daily use. Their advantages are lower acquisition costs and lower values of self-discharge current. Therefore, they are primarily used in devices that must function reliably for a long time and simultaneously have low energy requirements – e.g., clocks, small flashlights, remote controls, detectors, monitoring cameras, etc.

Fig. 1. Batteries (primary cells)

Fig. 2. Accumulators consisting of a single secondary cell

Accumulators have the ability to store energy by recharging with electric current and can be used multiple times. Charging is a reversible electrochemical reaction.

The main part of an accumulator is a secondary cell, and usually, an accumulator consists of several such cells. A secondary cell is also called an accumulator cell.

In the that a secondary cell is equipped with elements for immediate use with everything that belongs to it according to relevant standards – including clear, visible marking – then a cell equipped in this way, even if it is only one, is also called an accumulator.

However, when it is a rechargeable cell that does not have all the attributes necessary for immediate use and was manufactured to become part of a more complex device, the correct name for such a "semi-finished product" is a secondary cell or an accumulator cell.

Secondary cells are often part of larger units. The final product is then a device consisting of a set of series, parallel, or combined connected secondary cells, including a housing, connectors, suitable control electronics, etc., and we call it an accumulator. The name "accumulator battery" is also often used and is equally acceptable.

Fig. 3. Secondary (accumulator) cell Samsung Li-Ion INR 18650-25R

Fig. 4. HERMAN BL 18V/5Ah Li-Ion accumulator as a system of series-parallel connection of rechargeable cells

Compared to primary batteries, accumulators have higher initial acquisition costs, higher self-discharge currents, and additionally require a suitable charging device.

The greatest advantage is resistance to high current loads and a high number of possible charging cycles – normally ranging between 100x – 1000x; with modern rechargeable batteries from renowned manufacturers (Samsung, Panasonic, etc.), their number reaches more than 1500. Their use is rapidly increasing, and they have an irreplaceable place in our daily lives, e.g., in mobile phones, cars, cordless tools, etc.

A Galvanic cell (sometimes inaccurately called a Voltaic cell), named after scientists Luigi Galvani and Alessandro Volta, is basically a type of electrical source capable of converting an electrochemical reaction into electrical energy. It consists of two electrodes connected by an ionic conductor, usually an electrolyte.

Fig. 5. Galvanic cell

Fig. 6. Voltaic pile – schematic representation – electrolyte (1), zinc (2), copper (3), cell (4)

According to historical records, Volta had not yet invented the galvanic cell, but in 1800 he invented the galvanic column, called the "Voltaic pile", which is historically the first electric battery. It is a galvanic battery formed by several series-connected electric cells with zinc and copper electrodes, separated by felt soaked in an electrolyte solution.

And exactly in honor of the inventor Alessandro Volta, born on February 18, 1745, February 18th is declared worldwide as "National Battery Day".