# PPT_CHAPTER_4

#### slide_1: Batteries

* Battery is a device which is used to store electrical energy in the form of chemical energy and to convert this chemical energy into electrical energy.
* The construction of battery consists of electrochemical cells, which consists of two electrodes, negative and positive electrode and an electrolyte in the centre.
* When the two electrodes are connected by a wire, electrons will flow from negative electrode to positive electrode. This flow of electrons is called electricity.
* The cell is considered to be dead when the electrons on the positive and negative electrodes are equal.

#### Slide_2: Battery Fundamentals

* Volt - The unit of measurement of electromotive force, or difference of potential, which will cause a current of one ampere to flow through a resistance of one ohm.

* Ampere-Hour: A unit of measurement of a battery’s electrical storage capacity. Current multiplied by time in hours equals ampere-hours.

* Watt - A measurement of total power. It is amperes multiplied by volts.

* Watt-Hour: A Watt Hour is a unit of measurement for power over a period of time.

* Cell - An electrochemical device, composed of positive and negative plates and electrolyte, which is capable of storing electrical energy.

#### Slide_3: Battery Fundamentals(Cont)

* Capacity - The capacity of a battery is a measure of the amount of energy that it can deliver in a single discharge.

* Direct Current (DC) – The unidirectional flow of electric charge. It is the type of electrical current that a battery can supply.

* Cycle - One sequence of charge and discharge.

* Charge - The conversion of electric energy, provided in the form of a current, into chemical energy within the cell or battery.

* Discharge - The conversion of the chemical energy of the battery into electric energy.

#### Slide_4: Battery Fundamentals(Cont)

* Battery-Charge Rate - The current expressed in amperes (A) or milli amps (mA) at which a battery is charged.

* Cycle Life - For rechargeable batteries, the total number of charge/discharges cycles the cell can sustain before its capacity is significantly reduced.

* Depth of Discharge - The amount of energy that has been removed from a battery (or battery pack). Usually expressed as a percentage of the total capacity of the battery.

* Energy Density: The volumetric energy storage density of a battery, expressed in Watt-hours per litre (Wh/l).

* Power Density: The volumetric power density of a battery, expressed in Watts per litre (W/l).

#### Slide_5: Battery Fundamentals(Cont)

* State of Charge [SOC]: SOC refers to the remaining charge in a cell as a percentage of the charge contained by the cell when it is full.

* State of Health [SOH]: The change in the amount of charge that the cells can hold as they age.

* C RATE: C rate of the battery is the rate at which the capacity of the battery is charged or discharged to the load.
Maximum Current Draw = Capacity (Ah) x C-Rate
Example, a 3S 2.5Ah 5C LiPo battery pack will draw a maximum safe current of
2500mAh x 5C = 12.5A

#### Slide_6: Mathematical Calculation

* Average Battery Current
IB=C/N
IB = Average battery current
C= Capacity in Ah
N= No of hours of discharge

Example:
For 10Ah of battery and 10hours of discharge
IB=30Ah/10h = 3A
It means that 30Ah of battery is capable of supplying 3Ah of average current to the load up-to 10hours. Though due to losses 30Ah battery can supply 3A average current for less than 10 hours.

* Continuous Discharge
2500mah battery with 5C rating
Continuous Discharge Amperage = (mAh/1000) x C Rate)
= (2500 /1000) x5=12.5A

* Run Time for Safe Continuous Discharge
2500mah battery with 5C rating
Run Time = (60min/C-Rate) = (60min/5) = 12min
Therefore, Discharge 25A for 12min

#### Slide_7: Types of Battery

The types of rechargeable batteries used in Hybrid Electric Vehicles and Other Electric Vehicles [EV] are

* Lead-Acid battery.
* Nickel-Cadmium Battery (NiCd or NiCad)
* Nickel Metal Hydride [NiMH] battery.
* Lithium-ion [Li-ion] battery.

Each battery type has its own set of advantages and disadvantages selection of these batteries depends on where it is used so that maximum benefit can be obtained.

#### Slide_7: Lead-Acid battery

* To convert chemical energy to electrical energy sponge metallic lead and lead peroxide are used.
* It is the oldest and the first rechargeable batteries made available.
* Advantages: low cost, long life cycle, and can withstand slow, fast and overcharging, it is available in all sizes and shapes, wide capacity range, low self-discharge- which is lowest among rechargeable batteries, high discharge rate, can be recycled and reused in new batteries.
* Disadvantages are energy density is low, poor weight-to-energy ratio, not environmental friendly, as it employs harmful chemicals transportation restrictions on flooded lead acid, limited number of full discharge cycles.

#### Slide_7: Nickel-Cadmium Battery (NiCd or NiCad)

* The rechargeable NiCd battery is composed of nickel hydroxide in the positive electrode, cadmium in the negative and potassium hydroxide as electrolyte.
* NiCad batteries will maintain a steady voltage of 1.2v per cell up till it is nearly completely depleted.
* Advantages are low internal resistance, wide range of sizes and performance options are available, high charge and discharge rate, lighter, more compact and higher energy density than lead acid batteries, self-discharge rate is lower than NiMH batteries.
* Disadvantages are expensive than lead acid, extremely toxic-causes environmental pollution, high self-discharge, low energy densities compared to newer systems.

#### Slide_7: Nickel Metal Hydride [NiMH] battery
* Hydrogen absorbing alloys are used as the active element at the negative electrode and Nickel-hydroxide at the positive electrode.
* Advantages are higher capacity than NiCd, environmentally friendly no toxicity issue, wide operating temperature range, transportation and storage is simple.
* Disadvantages are load discharge is high, generates heat during fast charge, sensitive to overcharge.

#### Slide_8: Lithium-ion [Li-ion] battery.
* NiMH and Li-ion came into view in 1990s and Li-ion became the most promising and the fastest growing battery system.
* Lithium offers the largest energy density and is the lightest of all the metals.
* Due to safety issues, attempts at developing Lithium-rechargeable batteries failed.
* There was a shift from Lithium to Lithium-ion, it is safer but lower energy density than Lithium metal.
* The subclass of the lithium-ion battery markets are
Lithium-Iron-Phosphate [LiFePO4]
Lithium- Nickel-Manganese-Cobalt-Oxide [NMC]
Lithium-Manganese-Oxide [LMO]
Lithium- Nickel-Cobalt-Aluminium-Oxide [NCA]
Lithium-Cobalt-Oxide [LCO] batteries.

#### Slide_8: Other Battery Technologies

1. Solid state battery:
The Solid-state battery employs a solid material for its electrolyte and replaces the liquid or polymer electrolyte.
The battery pack thus obtained possess higher energy density and hence reduces the cost per Kw in terms of commercialization purpose.
It also has higher durability, longer life and higher charging capabilities.

2. Aluminium-air battery:
The flow of electrons in this battery is produced due to the reaction of oxygen in the air with aluminium.
These batteries possess one of the highest energy densities among all the batteries.
An EV equipping such batteries can offer up to eight times the range of an EV with a conventional lithium-ion battery while occupying significantly less space.

#### Slide_9: Battery Pack

The following parameters are considered while opting for a battery pack:

* Life span: The battery pack of an EV has a life cycle of 8 years or 160,000 Km.
* Safety: A safe operation must be ensured by carefully designing a proper BMS for the rated application.
* Cost: A major disadvantage for EV’s is the cost is much higher than that of an ICE vehicle.
* Specific energy: The energy density is a measure of battery capacity in weight (Wh/kg) and the amount of energy stored per unit mass.

#### Slide_10: Battery Connection

* A battery pack consists of set of identical individual battery cells.
* They may be configured in parallel, series or combination of both to produce the desired voltage, capacity, or power density rating.
* Three types of Connection

1. Series Connection
2. Parallel Connection
3. Series-Parallel Connection

#### Slide_11: Series Connection

* In series connection voltages gets added and current remains constant.
* Two 3.6V 2400mAh batteries connected in series(2s)

3.6V+3.6V=7.2V
Thus forming, 7.2V & 2400mAh.

Series Connection

#### Slide_12: Parallel Connection

* In parallel connection increases the current rating keeping the same voltage rating.
* Two 3.6V 2400mAh batteries connected in parallel(2p)

2400mAh+2400mAh = 4800 mAh
Thus, 3.6V & 4800mAh
Parallel connection

#### Slide_13: Series-Parallel Connection

* By connecting two pairs of two batteries in series and then parallel, then this configuration is called Series-Parallel configuration.
* To get 7.2V and 4800mAh, cells must be connected in 2s2p format, meaning 2 cells in series (7.2V) and 2 cells in parallel(4800mah).

3.6+3.6=7.2V (2S connection)
2400+2400=4800mAh (2P connection)
Thus, 7.2V & 4.8Ah (2S2P)
Series-Parallel connection

#### Slide_14:Insulation and types of insulation

* Proper insulation of a battery pack is important to shield the battery from high and low temperatures respectively.
* These extreme temperatures can shorten the lifespan of the battery.
* Proper insulation also ensures that the system is not affected by external factors such as weather, dust or moisture.
* This not only prolongs the lifespan of the battery cells but also ensures safety.

#### Slide_15: Cell holders

* Cell holders are often used to provide rigid support to the battery pack structure.
Battery cell holders

#### Slide_16: Barley sheet

* Barley Paper can be used for insulation.
* Barley paper insulation provides high insulation, shielding and anti-interference.

Barley sheet insulation

#### Slide_17: Shrink Wraps

* Common methods of sealing the battery packs are using heat shrink wraps or putting the battery pack in some hardcase.
* Shrink wraps are available in multiple dimensions to suit different configurations.
* The shrink wraps are selected based on their width.

PVC shrink wrap