motorcycle Honda Numa Hybrid

Engineering Students Build 2 Wheel Drive Hybrid Prototype Scooter

In 2012 we can expect the fuel prices increasing to unimaginable levels. Gone are the days when petrol was available for 40 rs per liter. There is a reason why those fuel hungry yet fun, smoking 2 strokes were wiped out of the face of the planet earth.

Being a 2 stroke fan myself i can only dream about them making a comeback. Thats when four Automobile engineering students and our friends at VMKV Engineering college Salem, found a way to build a hybrid combining the good old 2 stroke fun, and practicality and efficiency of an electric motor.

The Hybrid.

In theory it works similarly to the much advanced hybrids available in the market. The fuel burning engine and the base vehicle is a TVS Scooty ES which displaces 59.9 cc. The 2 stroke aircooled single produces 3.5hp at 5500 rpm and 4.5 nm of torque at 5000 rpm. The electric motor/generator is fixed on the front hub on custom forks tricked out to accommodate the 250 watt brush-less DC motor.

Battery pack which powers the electric motor consists of four 20 ah 12 volt Maintenance free Li-ion batteries connected in series. Charging the battery is done by the electric motor itself in generator mode.

There are different ride modes and their custom made Electric circuit (ECU) switches and controls the running of electric motor/generator and/or engine according to the modes selected. Mode selection switches are fixed on the dashboard and their corresponding indicator LEDs which tell you which mode you are on are also fixed here. Layout is simple enough for everyone to understand.

Mode selection switches and indicator LEDs on the other side.

The custom made console houses a speedometer and a battery charge indicator gauge. The blue part on the speedometer indicates the electric motor to engine switchover range.

The riding modes are the most important aspect of the Hybrid and much work has gone into tweaking and polishing the modes to work efficiently.

Mode 1 – Petrol. This is the default setting and there is no switch for this mode. Scooter runs like every other petrol scooter. Battery charging happens during this mode at any given speed.

Mode 2 – Electric. When the toggle switch for this mode is activated the ECU automatically switches off the engine and the electric motor takes over. Maximum speed supported at this mode is 25-28 kmph.

Mode 3 – Power mode. This mode activates both electric motor and engine, bumping the torque and hp figures. Now the scooter turns into a 2 wheel drive fun machine till 25 kmph!

To ensure that the electric motor gets enough power for long enough, the ECU switches off the electric motor and turns it into a generator when the speed exceeds 25 kmph and initiates charging. When the speeds again goes down below 25kmph the ECU switches from generator mode to electric motor mode. In power mode the Scooty has enough power to propel a rider and a pillion on a steep uphill climb from a dead stop!

Mode 4 – Hybrid. This is the most interesting mode. When this mode is activated The ECU turns the electric motor on and switches off the engine till speeds not exceeding 25kmph.

When the rider twists the throttle and wants to go faster than 25 kmph the electric motor is switched off and it is turned into a generator by the ECU and the engine is switched on. This also initiates charging after 25 kmph. When the speed is again reduced to 25 kmph or lower the engine is switched off and the electric motor switches from generator mode to electric motor mode.

Now fuel efficiency is maximized. Pretty neat!

The Hybrid in action.

Along with all these modes the team also housed an external charging circuit for practicality. The scooter can be charged from any household 240 volt current outlet.

The 240 volt external input plug for battery charging.

Fuel efficiency has increased Emiison levels have reduced almost 2 fold. The engine when run on petrol alone delivers 40 kmpl. Now a stock Scooty ES will deliver about 50kmpl.

The reason for this low value is because of the electric motor/generator which puts a load on the engine. This is not a problem because the electric motor compensates for this 10kmpl decrease in engine efficiency when speed is below 25kmph.

When the engine burns one liter of petrol it will recharge the battery to 80% in Mode 1.  With an 80% charge the motor can propel you further for 35kms. That gives a combined fuel efficiency of 75kmpl! In full charge the battery can power the motor for 50kms and that along with 1 liter of fuel you can go 90 kms! For some who ride certain 100cc 4 strokes, this value is not sky high. But there were limitations because of the budget.

The battery for one has been bought second hand and  so are several other parts. With enough budget and support the Development team is confident that they can make the kilometer per liter value go past 100 and maybe a 150! We at Throttlers wish them all the best for their future endeavors.

The Development Team with their Hybrid. From left – Sajith Raj K, Arun B K, Akhil Ghosh, Dhanush K Dev. The team also like to thank their Head Of Department Mr. T Raja.

Engine – Aircooled 2 stroke single

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