Dynamis lead-line Technisch handboek - Pagina 10

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The above charging mode needs long enough time to fully charge the battery.

However, for charging the electric vehicle battery system with limited time,

the CICV charging mode may sometimes not be able to fully charge the

battery. If one battery is not fully charged in a long string of batteries, that

battery will have faster degradation and then cause a capacity loss of the

long string after many cycles of deep discharge. Such result comes from the

little differences in charging efficiency among different cells. In the constant

voltage charging stage, the current density is gradually decreased to a very

small value; it is difficult to allow all cells to have the same amount of

charge unless charging with long enough time. In discharge, all cells should

deliver the same amount of charge. In consequence, the lower capacity cells

will experience deeper discharge and faster degradation.



A three-stages charging mode is introduced for long string and deep

discharge cyclic applications, which would allow every cell to be fully

charged in short duration. The first two steps are the same as the CICV

method, with the modification that the constant current should be larger than

0.6CA and may be as high as 2CA for some electric vehicle battery

applications. The constant voltage step may be lasted for 1 to 3 hours with

voltage limit of 2.4~2.5V/cell. A third stage is added and it is the constant

current charging with current density smaller than 10-hour rate (10-hour to

40-hour rate), and with duration limited to 1 to 2 hours. In this third stage,

there is no voltage ceiling, although the cell voltage will always be finally

flattened around 2.65 ~ 2.75V/cell. The voltage of the final stage may seem

too high, however, with the small current and short duration restriction, the

negative effect on the battery is minimized.

DYNAMIS Batterien GmbH

Tel. +49 7735 93669-0

Brühlstr. 15 D-78465 Dettingen / Konstanz

Fax +49 7735 93669-91

www.dynamis-batterien.de

04.12.2006

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