Project 2

a.The max heat generation of the battery:

Theory:

 Heat Generation:

As we need propulsion power to run a vehicle which is for an EV – possible by using the needed heavy voltage battery packs?

 Heat is generated when the battery pack is being Used and during charging as well.

Therefore, it is necessary to evaluate the battery heat generation to maintain the level of heat within safe limits for safety and durability, better performance.

 Operating temperature of lithium-ion battery is an important factor influencing the performance of

 Electric vehicles. During charging and discharging process, battery temperature varies due to internal heat generation, calling for analysis of battery heat generation rate. The generated heat consists of Joule heat and reaction heat, and both are affected by various factors, including temperature, battery aging effect, state of charge (SOC), and operation current.

In this article, a series of experiments based on a power-type lithium manganese oxide/graphite battery was implemented under different conditions. The parameters for Joule heat and reaction heat are determined as well as the total heat generation rate is detailed and analyzed considering the influence of temperature, aging, SOC, and current. In order to validate the accuracy of heat generation rate, a lumped battery heat transfer model is applied to calculate the temperature variation, and the estimated temperature variation shows good correspondence with experimental results under different currents and aging conditions. Due to its simplicity, the temperature variation estimation method is suitable for real time applications.

What factors affect the generated heat in a battery?

 The generated heat consists of Joule heat and reaction heat, and both are affected by various

 factors, including temperature, battery aging effect, state of charge (SOC), and operation

 current. 

 Controlling the heat buildup in EVs:

 Battery thermal management is a huge challenge in electric vehicles. In addition to increasing the risk of fire, high temperatures can have a direct influence on range. By efficiently controlling EV

 Temperature levels, battery range can be maximized. 

  Just like internal-combustion engine vehicles, when an electric power train works harder, it gets

 Hotter. Therefore, EVs require effective, efficient and durable cooling systems. Heat management can have a major impact on not only the components within a vehicle, but also its overall performance.

 Importance of Thermal Management for EVs?

 TMS is generally used for batteries operating under a high discharge rate, and especially for a large-

 Scale battery pack that requires a long life cycle (>10 years) and is pricy to replace.

The factors that are traditionally considered in the TMS trade-off analysis include energy efficiency,

 Capital costs, ease of operation, maintenance requirements, and reliability. Cold plate and

 thermoelectric devices are not recommended for use in commercial systems, owing to their high

 thermal resistance and low coefficient of performance, respectively.

Battery Thermal Runaway in Electric Vehicles:

Thermal runaway begins when the heat generated within a battery exceeds the amount of heat that is dissipated to its surroundings.

 What causes the battery to overheat which leads to thermal runaway?

  1. Ambient Temperature

  2. Age of the Battery

  3. Float Charging Voltage

  4. Overcharging

 Approaches to Minimize Thermal Runaway

 The reduction of the Thermal Runway hazard can be fulfilled on three levels-

 1.  First: improve the intrinsic safety of anti-TR properties by material modification;

 2. Second: set passive defense against the practical abuse conditions and develop an early warning

 Algorithm before TR;

 3. Third: postpone or inhibit the secondary hazard, such as Thermal Runway propagation, to win

 Sufficient time for the passenger to escape from the EV after the accident

 Formula:

 Heat Generation = Joule Heat + Entropic Heat

 Joule Heat = i^2 X r X t

 Where, t = time (sec/hr)

  i = battery current (A)

  r = resistance (mohm)

  Joule heating, also known as ohmic heating, is used to directly heat water with electric current.

 Joule heating is sometimes also referred to as ohmic heating or electrical resistance heating. It refers

 to the method of heating electrolyte-filled water by exposing it directly to electrical current.

 The entropic coefficient of a lithium-ion battery cell is used to calculate the reversible heat of a

 Battery during operation, which is a no negligible part of the battery thermal modeling.

 SOC % (State Of Charge) of a Battery pack:

  The SOC is the measurement of the amount of charge remaining on a battery. It represents the ratio of the current capacity of the battery to its nominal capacity after a period of use or long-term

 shelving, which also indicates the maximum amount of power that can be stored in the battery. The

 SOC is calculated as a percentage: when it’s at 0, it means the battery is completely discharged.

 When the SOC is at 100, it means the battery is completely full.

<!--[endif]-->

 Absolute Charge State

 There is also what’s called an absolute charge state, which is a reference value calculated from the

 fixed capacity value when the cell is manufactured. The absolute SOC of a new fully charged battery is

 100% while an aged battery, even if fully charged, cannot reach 100% in different charge and dis-

 charge situations.

 Influencing Factors

 Most SOC estimations require precise data measurements, whether it is the chemistry of the cell (type

 of electrolyte), its operating conditions, or the variables of the cell (voltage, current), etc., thus being

 suitable only in the laboratory and not in real applications. The SOC of a battery is a combination of

 voltage, charge/discharge current and internal resistance parameters to estimate its size. These

 parameters are also affected by a variety of uncertainties such as battery aging, temperature changes

 and usage status.

 Accurate SOC estimations reflect important information, such as battery performance, remaining

 battery life, etc., which ultimately leads to efficient management and utilization of battery power and

 energy. In addition, SOC estimation can be used to regulate battery life degradation, explosions or

 fires due to battery over-discharge and overcharge, as well as aging and permanent damage to the

 battery cell structure. Therefore, the SOC indicator on a BMS is vital for user convenience, as well as

 the efficiency, safety and life of the battery.

 We can observe that the SOC% is discharging and charging in the above output by its simulink model connectivity .The positive symbol of the battery is connected controller current source negative and negative of the battery is connected to the positive of controlled current source and the controlled current source is connected to the signal builder to check the battery operation for 208 seconds 

As we can see the both charging and discharging the SOC has been decreased only 1% of the battery as we can observed and also my drive cycle has been shown for the 208seconds as required.

Data input & signal conversion

output:

Conclusion

A Battery model is designed in the Simulink with the given currents data and given specifications, Calculated SoC% for 208seconds of simulation run time, and also Calculated Maximum heat generated in the battery.

 

We can observe that the SOC% is discharging and charging in the above output by its simulink model connectivity .The positive symbol of the battery is connected controller current source negative and negative of the battery is connected to the positive of controlled current source and the controlled current source is connected to the signal builder to check the battery operation for 208 seconds 

As we can see the both charging and discharging the SOC has been decreased only 1% of the battery as we can observed and also my drive cycle has been shown for the 208seconds as required.

------------------**----------------------------**--------------------