What Is SoH In Battery, State Of Health, Methods, Purpose

October 13, 2020January 7, 2023 CS Electrical And Electronics

Hello guys, welcome back to our blog. Here in this article, we will discuss what is SoH in battery (state of health), methods to estimate the SoH, and why SoH estimation is needed.

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What Is SoH In Battery, State Of Health

SoH (state of health) is expressed in percentage and is nothing but comparing the present cell capacity with the initial capacity of the cell. The cell capacity will vary after a number of cycles of charging and discharging. So, to find out the quality of cells after a number of cycles, an SoH estimation is needed.

The increasing number of fossil-fuel-driven internal combustion engines (ICEs) has a significant effect on global climate transformation, energy usage, greenhouse pollution, and health hazards. As a consequence of this worrying crisis, several nations have started to put a more significant focus on renewable and green energy sources to substitute fossil fuels.

According to a statement by the Transport and Environment (T&E) community, the transportation enterprise alone accounted for 27% of general European Union greenhouse gas emissions. Passenger automobiles account for 41% of total vehicle pollution.

The car enterprise has recognized electric vehicles (EVs) as the excellent solution to appearing challenges and problems associated with climate change and rising energy demands.

Because of their increased electric capacity, high precise energy, increased charging efficiency, extended lifespan, lower maintenance, and lower self-discharge, lithium-ion batteries (LIBs) are a preferred option for the automotive enterprise BMW Mini E, Tesla Model S, GM Chevy-Volt, Renault Zoe, Chrysler 200 C EV, Nissan Leaf EV, and Mitsubishi iMi EV nearly all EVs on the road.

EV batteries must be managed more efficiently to extend the driving range, optimize power consumption, extend battery life, boost battery efficiency, and provide safe operations. In public, the electric vehicle uses a true module called a battery management system (BMS) to confirm that the battery is secure and efficient.

Inappropriate battery maintenance can donate to security problems such as quick battery aging and extreme heat, which can conduct in an explosion. One of the most significant BMS operations is the actual measurement of the battery’s state of health (SOH).

This guarantees that lithium-ion battery conduct healthily and predictably by estimating their remaining lifespan and indicating their failure condition.

Why SoH (state of health) estimation is needed?

HEVs (hybrid electric vehicles) and EVs (Electric vehicles) have been identified as the most viable alternatives to living internal combustion (IC) engine-based automobiles and their production has grown in current years.

Due to several benefits such as increased energy capacity, insufficient environmental emissions, and extended cycle life, batteries have become a standard power source for HEVs and EVs.

A well-thought-out charging scheme would protect batteries, decrease temperature variations, and enhance energy modification efficiency. Slow charging limits the availability of EV use, whereas charging too fast results in significant energy loss and temperature increase.

As a consequence, the battery management system (BMS) is essential for maintaining battery safety and implementation. Battery simulation, internal state estimation, and battery charging are all appropriate developments in the BMS of electric vehicles.

Battery pack states monitoring, real-time controller tuning, thermal management, battery behavior research, and fault diagnosis are all useful from an optimized battery model.

Similarly, some of the inner battery states such as state of health (SOH), state of charge (SOC), and internal temperature are challenging to determine explicitly even though these states play important functions in regulating battery operation and must be monitored utilizing practical estimation approaches.

The factual state of health (SOH) computation of lithium-ion batteries allows users to make wise replacement decisions and lower economic losses. SOH computation accuracy is related to multiple factors, such as use time, ambient temperature, discharge and charge rate, etc.

Most specialist service techs decide that you should replace your automobile battery every four to five years. Nevertheless, there are multiple factors that can affect a battery’s life.

SoH (state of health) estimation methods

Here you have to estimate two things: one is SoHR and another one is SoHC. SoHR means after a number of cycles the cell’s internal resistance will start altering, so it is important to estimate internal resistance to replace cells after a certain limit. SoHC means the estimation of the capacity of the cell. After a number of cycles, the capacity of cells will start degrading, and estimating SoHC will tell us when to replace the cells.

There are various methods used to estimate both SoHR and SoHC. That is;

01. Simple method: For SoHR you can use this simple formula, rate of change of voltage divided by rate of change of current. And for SoHC you have used this formula, (present capacity / initial capacity) * 100.

Let us discuss some other methods for SoH estimation.

02. Direct measurement:

Impedance: Electrochemical Impedance Spectroscopy (EIS)
Ohmic Resistance: Current Pulses

03. Model based on measurements:

Data Maps
probabilistic method
Support vector algorithm
Parity relation
Sample entropy
Coulomb counting
Big data

04. Adaptive battery methods:

Kalman filters
Neural networks
Fuzzy logic
Observers
Last squares

These are some best methods to estimate the SoH of the battery. The SOH of a battery is usually defined as the battery’s performance at the current time corresponding with the implementation at ideal conditions and the battery’s new state. The computation of the battery’s SOH has to take into regard both the battery capacity fade and the impedance increase.

The decision of the SOH can be done by two separate methods including data-driven and adaptive systems. In the data-driven part, with the cycling data and the primary parameters concerning the battery lifetime, an computation of the SOH can be achieved.

Deep knowledge of the correlation between the process and degradation through physical analysis or the evaluation of large data sets is required for this method.

This was about “What Is SoH In Battery, State Of Health“. I hope this article may help you all a lot. Thank you for reading.

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