Growing popularity of battery cells in Lithium-Ion technology is justified by its excellent parameters, like large electrical capacity for weight unit, unsignificant self-discharge and memory effect absence. Advantages of lithium-Ion cells with growing demand on alternative energy source for vehicles (EV and HEV), cause rapid interest in batteries of serially connected lithium-ion cells. Such a batteries offer large capacity and high voltage to power the drive system, which is a condition to limit currents and efficiency increase.
Electrical energy storage in multicell serially-connected battery pack generates several problems that can lower the efficiency and operation safety:

• battery charging only to the moment, when any of serially connected cells achieve its maximium allowable charge level, exceeding the allowable charge level may lead to cell degradation or even to the explosion
• battery discharging, only to the moment, when any of serially connected cells achieve its minimum allowable discharge level, exceeding the allowable discharge level may lead to cell degradation
• charging is not a constant process, it depends on charge level of the cells
• cells temperature in charge and discharge phase may not exceed the allowable limits

Lithium-Ion battery is expensive, and its proprer operation, determines the proper operation of a powered device (i.e. electrical car). From the proper operating battery pack we expect the following results:

• possibility of safe charging serially connected battery cells, in which each of the cell in battery achieve its maximum allowable charge level;
• possibility of safe discharging serially connected battery cells, in which each of the cell in battery achieve its maximum allowable discharge level;
• complete information of each cell voltage and temperature for safety operation of the whole battery pack;
• complete information of charging and discharging current flows in battery, that allows to calculate accurate value of charge remaining in battery

Cells serially connected in battery are never identical, and what’s more initial differencies in particular cell parameters intensify during operation. Such an effect causes, that achieving above-mentioned objectives demand an advanced measurement techniques and specialised charge management systems. EVE tech team elaborated the metod that allows to safe and optimal operation of HV Lithium-Ion cells in battery.

If you are interested in battery management, do not hasitate to contact us

Janusz Mendel – CEO
jmendel@eve.com.pl
phone +48 22 783-51-12
fax +48 22 783-55-04