Electric Vehicles

Every BMS measures only three vital parameters of the battery which are the Voltage, current and Temperate of the cell. It constantly compares these values with safety limits and disconnects the load if they exceed the threshold values. Apart from safety purpose the BMS is also used for some computational purpose, like measuring the SOC and SOH of a battery.
SOC stands for Sate of Charge and SOH stands for State of health. Unlike an ICE Car the amount of fuel left in the battery cannot be measured by directly look at it. Some people even think that measuring the voltage across the terminals of the battery can give you the battery capacity, well it’s not true and it is not that easy. Similarly SOH gives the life expectancy of the battery. Both SOC and SOH are vital information for a consumer since SOC tells you how far you can drive before recharge and SOH tells you when it’s time to replace your batteries. It is the duty of the BMS to measure both these parameters. How does this measuring take place is totally a different story and we will cover in a separate article.
BMS circuits are often complex, a simple 4 Cell Lithium BMS is shown in the picture below. Imagine the BMS of a car that has to monitor around 7000 cell.

Electric Vehicle Motors

While batteries are the fuel tanks of an EV, the motors are the Engines of them. There are many types of Motors used in EV and the one used for Scooters and bikes is totally different form the one that is used in cars. Let’s have a quick look on the commonly used ones that are BLDC motors, Brushed DC motors and AC Induction Motor. A more detailed article on EV motors will be covered later.
BLDC Motors: BLDC Motors have been the choice for EV’s from its origin in 1900. Even today it is commonly used in Electric cycles and scooters. BLDC stands for Brush Less DC motor, these motors have a constant torque and fast response making it suitable for automotive applications. Apart from EV’s these motors are also used in wipers, power windows etc. The BLDC motor for EV can again be classified into the following two types

BLDC Hub Motors

In BLDC Hub type motor, the rotor of the magnet is the wheel itself, meaning there is no need of coupling arrangement since the rim of the wheel forms the motor. These motors are also called as the BLDC out runner motor. Advantage of this type of motor is that there is less mechanical loss and since there is no transmission unit cost and weight is reduced. Downside is that we cannot have gear ratio of high power motors due to size limitations. A BLDC hub motor of scooter is shown below. Almost all electric cycles and scooters you find on road uses such type of motors.