What is Powertrain in EV Vehicles?

Figure : EV drivetrain architecture (reference : MDPI energies).

The Powertrain in EV Vehicles are responsible for delivering and managing electrical power to move a Vehicle.

The EV Power train consists of  below components and systems,

1. Batter Packs (Lithium Ion Battery);
2. Inverters or MCU(Motor Control Unit);
3. E-drive (PMSM Motor);
4. VCU(Vehicle Control Unit;
5. i-PDU(Integrated Power Distribution Unit or All in one combo PDU);
6. Mechanical Transmission (drive shafts, differential gears & EV axles );
7. Thermal management systems ( Liquid Coolant Unit,Refrigerent Unit,Cabin air HVAC Unit).
   

References:

• Fault Diagnosis Methods and Fault Tolerant Control Strategies for the Electric Vehicle Powertrains

Memory Effect in Batteries

 Memory Effect:

These are observed mostly observed in NiCd Batteries and the battery loose its maximum energy capacity because of  repeated charging after only partially discharged. 

It Means : Battery is not fully discharged instead but charged to full repeatedly.

This effect is also known as battery effect,lazy battery effect or battery memory.

This effect was first observed in Satellites where the solar power was used to charge the NI-Cd battery and since satellites in the orbits revolve round the earth it has to go behind the earth and doesn't get any sunlight for some time and it has to use battery power for its operation.

The batteries utilizes suns power at day and battery power at night but it wont utilizes complete energy, hence the battery is getting discharged only 30% SOC and recharged to 100% for thousand of times, the NI-Cd remmembered it ( In Chemistry terms ), and the remaining 70% of the battery capacity was lost.

How to Mitigate Memory effect: 

1. The Memory effect can be mitigated by discharging the battery completly untill the battery ceases to function, then charge it to 100% SOC.

2. Try to discharge the battery pack completly and charge it to full atleast once in a month.

Fortunately Lithium based Batteries are not subjected to memory effects or Lithium batteries have no memory effects.

Motors used in Electric Vehicles

 

Below are the major motor types used in electric Vehicles,

1. Permanent magnet synchronous motors (PMSMs)

2. Induction motors

3. Brushless DC (BLDC) motors

What is Energy Density?

 It means the amount of energy that can be stored in a given Battery / substance / system/ a region of space.

For eg:

A simple analogy is the amount of water a water Bottle can hold is the capacity of that water bottle and the amount of density can change depends on the type of water (Hard or soft).

Same way, Energy Density of a battery Pack can be calculated as  V*Ah/Kg = Wh/Kg.

V = Nominal Battery Voltage
AH = Rated Battery Capacity
Kg = Battery Weigh

What is C Rate?

C rate was developed by French Scientist & Physicist Charles Augustin de Coulomb and is derived from Coulomb's Law

 It means the rate at which a battery is getting charged or discharged.

The C rate depends on the type of battery chemistry used and also depends on the manufacturer.The higher rate of charge like 1C means the battery can be charged more quicker then 0.5C rate of charge.

The higher C rate is suitable for applications like Grid balancing,Frequency regulation,Electric Vehicles etc

For eg: 

1C - Take 10AH battery it can able to charge and discharge at the rate of 10A for 1Hr or 1A for 10Hr.
0.5C or C/2 - Same 10AH battery can able to charge and discharge at 5A for 2Hr (10/2 = 5A).
2C - Same 10AH battery can able to charge and discharge at 20A for 30min (10*2 = 20A).
5C - Same 10AH battery can able to charge and discharge at 50A for 12min (10*5 =50A).