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Understanding Sub-systems of a Light Electric Vehicle

Battery:Battery is a device that converts chemical energy into electrical energy by means of electrochemical reaction. This is the source of energy for an E-bike which is similar like petrol in an automobile.

As petrol to be refilled after the day’s ride, same is the case with the battery too. Battery has to be charged daily.For measuring the capacity of the battery we use Ampere hours (AH).In E-bikes, the battery capacity is 20AH. This means that the battery lasts for 20 Hours if the discharge is 1 A continuously.There are different battery technologies namely, Lead acid, Lithium ion, NiMH etc.Lead acid is cheapest of all and suitable for the E-bike application. Lead acid batteries use liquid electrolyte. This is acceptable for the applications where the batteries used for still applications.

E-bikes are basically bumping and vibrating depending upon the roads. Hence the Basic Lead acid cannot be used as the liquid electrolyte will be spilling out which is dangerous to the person near by.

VRLA and SLA batteries are basically Lead acid based. The battery should be non-spill. Hence the two types Lead acid batteries came to existence.  

• VRLA batteries ? Valve regulated Lead acid. This is basically regulated by a value. The valve does not allow the inner liquid to spill out during the driving time. This provides safety.
• SLA Batteries- Sealed Lead acid. This battery is totally sealed, so that the liquid electrolyte don’t spill out. This has disadvantage, no maintenance can be done.

Brushless DC Motor

• Hub motor: is directly connected to the wheel. Hence the motor operating speed is same as required wheel speed. This is in the range of 380 rpm (revolutions per minute). The motor is heavy when compared to Geared motor. Power density is low when compared to a geared motor. Efficiency is better for Hub motors as there are no Gears involved in it.
• Geared motor are compact and have high power density. This means for the same power, geared motor is smaller size compared to that of hub motor. The motor inside the gear motor will rotate at high speed and low torque. The gear system will reduce the speed proportionally and increase the torque proportionally.

The traditional motors which are being used till recently are DC Motors. There are many problems associated with DC motors. They are as follows

1. The brushes present in the DC motor are subjected to wear and tear which needs periodic maintenance at least six months once.
2. The speed is constraint as the stationary parts are physically in touch with rotary parts.

The above problems are solved if we use brushless DC motor as it is giving us many advantages over DC motors.

The advantages of BLDC over DC motor are as follows

1. BLDC motor has very high power in a given volume. This is known as high power density. This high power density is due to the usage of permanent magnets.
2. Due to absence of brushes, there is no need of periodic maintenance. The motor once fitted need not be dis-assembled over its life time.
3. There is no contact between rotor and stator parts while running, hence this technology is not constrained to speed

Power Electronic Controller

A power electronic based controller being used to control the operation of the bicyle. Various aspects a controller can do are Controlling the electric motor operation, electrically stopping the motor while braking, speed measurement, regenerative braking and any other features.

DC-DC Converter

This converter used to reduce the high voltage to low voltage ( usually 12V) for supplying to the lighting circuits.

Wire Harness

Wire Harness is the wiring pattern connecting all over the bike accessories for their proper operation.