CONTEXT

Lithium ion batteries are widely spread nowadays to power most of electronic devices and even for electric vehicles or energy storage systems. Lifetimes of these batteries are related to their way of use and BMS are mandatory to control charge level, to balance between the cells in a battery pack,…
The determination of the State of Health (SOH) is an important part of BMS for EV or HEV batteries.

TECHNICAL DESCRIPTION

The invention relates to a new method to evaluate the state of health of lithium ion battery.
In BMS, SOH is evaluated through the measurement of parameters related to the performance of the battery (usually internal resistance and capacity).

The charging process of industrial lithium ion battery is performed in two phases. A first step with a constant current, and a second step with a constant voltage. This second step is stopped when the current reaches a specified low value.

Development stage

The invention uses the time of the CC-CV charge process in order to evaluate the SOH of the cell. A simple exponential model easy to implement shows a good fit with experimental data. The model was tested for the main cathode materials (LMO, NCA, NMC). The model could be adapted to fit the specific behavior of LFP cathode.

INDUSTRIAL APPLICATIONS

BMS

For further information, please contact us (Ref 02381-01)