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Li-polymer batteries.

Today there are some types of lithium batteries:
- lithium iron phosphate;
- Lithium - iron-sulphide;
- Lithium–titanate;
- Lithium-ion;
- Lithium-polymer.
The first three types of batteries occur rather seldom and they didn't receive wide application at present. Main and most commonly used current sources in various devices are li-polymer and lithium - ion batteries.
The lithium-ion battery has a large number of varieties, it is widespread in the modern world. At present it is one of the most popular current sources used in portable equipment (cell phones, photo/video cameras, laptops).
However, gradually lithium - ion batteries are displaced by newer lithium - polymer batteries. Service life of li-polymer batteries makes about 400-500 cycles. The quantity of cycles can vary depending on quality of production and characteristics of batteries.
Producers of li-polymer batteries are constantly improving the production technology and quality of batteries, which influences the service life positively.

Types of li-polymer batteries and application fields

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We divide li-polymer batteries into three groups:
-- Standard li-polymer batteries
-- Li-polymer batteries with the increased capacity
-- Li-polymer batteries with high discharge rates
The first group contains batteries which capacity doesn't exceed 6Ah, batteries belonging to the second group have capacity above 6Ah, the third group represents batteries with the various capacities which discharging rates begin from 5C.
Standard batteries are applied generally in electronic devices where compact sizes and low current consumption are necessary.
Batteries with the increased capacity are applied as a source of current in devices, the main requirement to which is longtime self-contained operation from one charge.
Batteries with high discharge rates found their application in model making (air, auto etc.), as current sources for electric cars, i.e. where high electrochemical capacity is required.

Assemblies of batteries

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The increase of capacity and electrochemical capacity is also possible by the means of assembly of batteries.
Assemblies can be parallel and consecutive, including a combination of parallel and consecutive assembly at the same time.

Producers of batteries put marks, basing on which it is possible to define the quantity of elements the ready battery consists of and how they are connected between each other. The parallel connection is marked by a letter P, the consecutive – S. At the parallel connection of batteries there is an increase of the general capacity (i.e. the parallel connection with a capacity of 5Аh 3.7V of two batteries will give a total capacity of 10Аh with voltage of 3.7V).
The consecutive connection increases a nominal voltage (i.e. the consecutive connection with a capacity of 5Аh 3.7V of two batteries will give the battery with the capacity of 5Аh with a nominal voltage of 7,4V).

It is important to know:
- At independent assembly of batteries it is necessary to carry out balancing of each cell;
- It is impossible to assemble the batteries differing on capacities in assembly;
- To replace old jars in assembly with the new ones.
It is worth using modern chargers which have built-in balance weights while charging the batteries. By the means of such chargers it is possible to charge all cells in the battery with adherence to all necessary parameters.

Li-polymer batteries.

Li-Ion batteries are applied in portable computers, cell phones and communicators. Most producers are constantly improving chemical properties of the batteries and also expand the field of application and provide various improvements every six months or even more often.

Many producers specify their batteries of this type for working at temperatures up to -20 °C, and thus they are capable to put out 60-70% from the nominal capacity under small loading. Nevertheless at big currents output falls to 40%. Though at temperatures close to 0 °C the capacity reduction of lithium - ion batteries is insignificant.

Due to high characteristics, high power capacity and also the length of the charge storage period these batteries are popular for use in small-sized mobile equipment. Nevertheless today they are most expensive among the available batteries in the market. They don’t come in AA and AAA consumer formats, they have non-standard voltage of 3,6 or 7,2 V (it is connected with chemical components applied in them), and also if damaged they are inclined to detonation at intensive charging. Though any of the damaged batteries can blow up, so treat them more carefully. Lithium-ion batteries also possess very high energy density.

 

 

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