SOC-ASIC (State-of-Charge-Application Specific Integrated Circuit), A Battery Voltage Monitoring System for Series-Connected Battery Cells in Electric Vehicle for State-of-Charge Estimation

Author Name(s): Nakul K Pathak, Prasad R. Pande, Lokesh Heda, Parag Jawarkar
Author Email: pathaknk@rknec.edu

Abstract

Increasing Green House Effect and reducing fuel storage of planet contributed highly due to automobile industry drives an alarming situation for researcher to look for alternative options for future generation vehicle. Tesla, Mahindra-eco and other automobile companies have already come up with concept of e-vehicle whose soul is battery and brain is Battery Management Unit. Our proposed design embodied SOC-ASIC (State-of-Charge-Application Specific Integrated Circuit) design for SOC (State-of-Charge) estimation of Series-connected Li-ion Battery cell used to build battery pack of hybrid or all- electric vehicles. It consists of high precision Array of dedicated instrumentation amplifier circuit which connects output voltage of terminal across each individual cell to ADC via array of switching network. Array of switching network consists of low power, low loss, and low threshold voltage switches driven by output of de-multiplexer circuit whose select lines controls from General Purpose Input-Output (GPIO) pins of microcontroller. Signal voltage after switching network process with Noise filter and Kalman filter to produce accurate and precise terminal voltage to ADC. Keywords Kalman Filter, Electric Vehicle (EV), State of Charge (SOC), Battery Monitoring.

Introduction

At the 16th Conference of the Parties held in 2010, Parties to the UNFCCC agreed that future global warming should be limited below 2°C relative to the pre-industrial temperature level [1] [2] [3].NASA’s Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880. Twothirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade. But why we should care about one degree of warming after all, the temperature fluctuates by many degrees every day where we live. A onedegree global change is significant because it takes a vast amount of heat to warm all the oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age [4]. Majorly the reason for Green House Effect is Green House Gases, which are water vapor, carbon dioxide, methane, nitrous oxide, and ozone, of which human activities have produced a 40% increase in the atmospheric concentration of carbon dioxide (CO2), since the beginning of the Industrial Revolution (around 1750) from 280 ppm in 1750 to 406 ppm in early 2017 [5].

Conclusion

This paper has proposed a scheme for State of charge estimation using dedicated Application specific Integrated circuit which is specifically designed for Battery Management Unit for Electric Vehicle. The proposed design embodied an Array of one-to-one high precision Instrumentation amplifier which utilizes to convert floating output into grounded output which can then forwarded via switching network which is controlled by demultiplexer whose select line are attached to GPIO of controller which stores data of individual voltage level of beach battery cell from battery pack. The feasibility of the balancing method has been verified by connecting 3 lithium-ion batteries in series in loading condition. The switching network is controlled by giving select inputs to demultiplexer which in turn operates switches one by one based on delay given from microcontroller. Result shows successfully voltage levels from individual battery cells, which are connected to dc motor (loading condition), can be retrieve even in loading condition

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