Development of status detection method of lithium-ion rechargeable battery for hybrid electric vehicles

In order to maximize the performance of lithium ion batteries, we have developed a new method for detecting the status of hybrid electric vehicle (HEV) batteries. The method obtains an accurate state of charge (SOC) by combining the SOC based on open circuit voltage (OCV) and the SOC based on current integration. In addition to that, our method has an auto-tuning function, which is realized by relatively simple processing, for the characteristic parameter of batteries. Our method can also obtain the state of health (SOH) by watching the tuned characteristic parameter. We perform simulation evaluations of our method with a battery model, and we confirm that the SOC error is less than 5% even if SOH set in the battery model and in our method are under mismatched condition. We also confirm that the SOH gradually converges to the true value and SOC error is improved by performing simulation evaluation repeatedly.

Automated summary

A new method is developed to detect the status of HEV batteries, accurately obtaining the state of charge and health of the batteries. The method also has an auto-tuning function for battery parameters, as confirmed by simulation evaluations showing less than 5% SOC error. The state of health gradually converges to the true value by repeated simulation evaluations.