Week 5 Challenge

ANSWER : 1

• The aggressive driver accelerates rapidly and brakes harshly.
• This requires the instantaneous high power to meet this condition.
• By operating battery at this condition increases depth of discharge and it degrades the battery.
• Battery pack has less specific power capacity than ultracapacitor.
• In order to meet this amount of peak current, the battery has to designed as per this condition.
• Hence the battery pack size and cost also increase.
• For this instantaneous high power for short duration of time, it is not efficient to increase the battery pack.
• But ultracapacitor has ten times high specific power than battery.
• The specific power is about 10kW/kg.
• Hence it can take care of peak loads.
• Thus, the sudden load can be used to meet sudden acceleration and braking.
• Sudden braking produces high regenerative current. This current can be used to charge the battery but it is not efficiently used.
• Because the battery must be charged in the particular charging rate.
• Ultracapacitor can be charged and discharged quickly.
• So, this current can be used to charge the ultracapacitor.

Hence, Ultracapacitor is the better choice to supply the power for the aggressive driver who accelerates and brakes rapidly.

ANSWER : 2

Energy Density: It is the measure of how much energy a battery contains in proportion to its weight. This measurement is typically presented in watt-hours/kilogram. The higher the energy density, the longer the runtime.

Lead Acid batteries:

Lead-acid batteries have relatively low energy density.

Nickel-Cadmium Battery:

Nickel Cadmium has a much higher energy density compared to lead-acid batteries.

Nickel-Metal Hydride Battery:

Ni-MH batteries can have two to three times the capacity of NiCd batteries of the same size, with high significance and also much less than lithium-ion batteries.

Lithium-ion battery:

Lithium-ion batteries have a high energy density.

Ultracapacitor:

Energy density is more in ultracapacitors compared to capacitors.

The values of energy densities of different batteries and cell voltage are shown in the below table and also the same is represented in the X-Y plot shown below.

ANSWER :3

Battery name	Power density (W/Kg)	Cell voltage (V)
Lead-acid battery	180	2.1
Nickel Cadmium	150	1.2
Nickel Metal Hydride	1000	1.2
Lithium-ion	340	3.6
Ultracapacitor	496	3.5

The power density plot of the batteries is shown below in the plot.

ANSWER :4

True. The number indicated as 1 is a -ve electrode.

Lithium-ion batteries generate DC power by utilizing chemical reactions.

• During discharge, lithium ions from the -ve anode move through the electrolyte to gets intercalate the +ve cathode.
• During charging, electrons move from anode to cathode in the external circuit.
• Electrons flow to balance the cell voltage.
• During the electrochemical process, the anode is -ve and the cathode is +ve.
• At the first time charging, the lithium-ion from the cathode gets attached to anode and it forms the inseparable layer on the anode.
• A solid Electrolyte Interface (SEI) is formed at the anode. Anode gets decomposed if it comes in contact with the electrolyte. SEI protects the anode.

A battery has just been manufactured in the industry and has been connected to a charger for the first time. The electrode marked as (1) in the picture below is the negative electrode. this is true.