• Karn Sinha

The Ola Scooter – Yet another story of impressive design let down by poor execution

Ola is arguably one of the most successful Indian tech startups in the last decade. The $7.5 billion ride hailing company has recently ventured into the e-mobility space. Ola’s ambitious plans have received extensive media coverage in the last couple of years, especially after the launch of their electric scooter. Unfortunately, their grand plans seem to be going down in flames, quite literally. There have been numerous instances of scooters catching fire across India. Furthermore, 1,441 scooters have been recently recalled due to safety concerns. The company is learning the hard way that hardware, unlike software, has a long maturity cycle and can’t be rushed. There is no such thing as a minimum viable product in the automotive industry.

I managed to get my hands on their newest electric scooter model, the Ola S1 Pro to see if it can live up to its hype.

A scooter that was designed for Europe is operating on Indian roads

The ola electric scooter is based on the AppScooter of a Dutch company called Etergo. Founders Marijn Flipse and Bart Jacobsz Rosier wanted it to be the 'Tesla on two wheels' when they started developing the scooter back in 2015. They had little success in the European market where they faced stiff competition from Chinese OEMs. The founders, who were on the verge of bankruptcy in 2020, sold the company to Ola for a bargain. More than six thousand investors, who have invested in the crowdfunded scooter, received €0.018 per share, Etergo said in an email. A pittance compared to the €0.40 per share that the company thought it was worth in November 2019.

Ola apparently spent a year making the scooter production ready for Indian customers. You would expect that a scooter that has been adapted for much harsher conditions would cost more. However, the AppScooter is priced at €3,400 in the Netherlands, whereas the top-of-the-line Ola scooter is a mere 1.2 Lakhs (approx. €1450). So where did Ola make most of these cost savings?

The only significant change made by Ola appears to be the battery pack. Ola uses a ‘banana’ shaped unremovable pack that is placed in the floorboard. The battery capacity has also been increased for the S1 Pro and charge times have been modified.

The overall structural design is inspired but not very robust

This machine's peak torque value is an impressive 58 newton meters, and its peak power is 8.5 kilowatts. The Ola scooter runs on an Internal Permanent Magnet (IPM) motor. These electric motors have permanent magnets embedded deep inside their iron rotors, which reduces demagnetization over time and gives them a longer service life. The IPM motor is a great choice for this application as it is high torque to weight ratios when compared with the brushless DC surface mount motors used in most other e-scooters. The IPM motors give higher torque for the same volume due to the additional reluctance torque the IPM's iron rotor provides. This results in greater acceleration when you start your Ola scooter.

The IPM motor requires an AC supply for its stator winding. To supply this power, Ola uses the banana battery pack, which is a collection of tiny cylindrical lithium Nickel Cobalt Aluminum oxides (NCA) cells. A three-phase inverter is used to convert the battery's DC voltage into an AC supply. A controller is also used in the scooter to modulate the frequency of the alternating current. When you accelerate the controller commands the inverter to increase the AC current's frequency, thereby increasing the speed of the IPM motor.

The scooter is noticeably quieter than its competition. The reason for the noise difference between the ola and other e-scooters is the transmission. As you can see the IPM motor is placed in the center of the Ola scooter and the rotational energy is transferred to the rear tire via a single stage belt transmission. Other scooters, for example, Aether use a two-stage transmission system to get high torque. The increased number of gears results in extra noise. Ola can manage with a single speed transmission because the IPM motor inherently gives a good torque output. The motor is placed in the center and not directly in the tire as a hub motor.

courtsey: the PluginIndia youtube channel

The reason this is done is to optimize the sprung to unsprung weight ratio. The unsprung weight is simply the weight of components resting over the suspension springs that move up and down with the scooter wheels. Sprung weight is shielded from the shocks and vibrations that the wheels experience as they travel over every bump and pothole. This makes for a more comfortable ride and protects the sprung components from destructive and life-shortening shocks and vibrations. If the ratio of sprung to unsprung weight is high, you get good travel comfort over speed bumps and potholes. Here you can see the motor is a part of the sprung weight.

If suppose ola used a hub motor with an in-wheel placement, the unsprung weight would increase, leading to discomfort while driving. For this reason, the ola electric scooter uses a mid-drive motor rather than a hub motor. Another design feature is the horizontal position of the shock absorber. This is called a cantilever suspension.

courtsey: the PluginIndia youtube channel

The animation above shows how cantilever suspensions work. One end of the suspension is connected to the chassis and the other to a triangular lever the lever is pivoted at this point the other end of this lever is connected to the wheel. By observing the animation, you can see that as the tire moves up and down the triangular lever rotates and transfers this motion to the shocks. This particular design enables the scooter to have a larger boot space.

One of this bike's coolest features is the regenerative braking which gives you more range. Here the motor acts as a generator the braking happens here without any metal-to-metal contact. Just by twisting the throttle in the reverse direction, the regen feature will give you more intense braking by reversing the direction of the stator EMF. This gives the reverse torque to the rotor and the motor comes to a sudden stop. Ola calls this feature a forced regen.

Despite these impressive features, the scooter has some major design flaws.

The first major design drawback is that during normal turns the handle reaches very close to driver’s knees, especially if they are tall causing discomfort.

Second, when the user tries to drive it on hyper mode, the scooter automatically switches to normal mode after some time due to the heating of the motor and battery. In hyper mode, the motor draws high power for a longer duration and overheats along with the battery. If this overheating continues the motor winding may burn and the battery can cause a fire. To avoid such a scenario, a smart battery management system is employed and is integrated with the battery pack itself. This electronic system signals the controller to switch back into normal mode as soon as the battery's temperature goes beyond safe limits. This solution eventually also saves the motor from damage. This feature is particularly important in India's warm environment.

The third drawback manifests itself during a hill climb with a pillion passenger. The scooter fails to fulfill the high torque demand required for this situation. This is probably because the scooter was originally designed for the Netherlands, which is very flat compared to India.

The final and most serious issue that we will examine further is the much publicized spontaneous combustion incidents. Government officials are still investigating the root cause but it seems very obvious why the scooter is catching fire. The original AppScooter was designed for European roads and Europe’s mild summer temperatures. Ola's founder Mr. Aggarwal had to make huge modifications to the scooter's design to make it viable for India’s bumpy roads and scorching summer temperatures exceeding 40 degrees celsius. They spent a whole year redesigning the scooter for the Indian conditions. In hindsight, one year of R&D seems insufficient to effectively achieve these adaptations.

Are Automotive Safety standards enough to make a reliable product?

The source of fires in EVs is almost always the battery packs. EV battery packs have up to three times the energy density of household products such as laptops. They also undergo more abuse in terms of temperature variation, moisture, vibration, and shock. A lithium-ion battery contains both an oxidizer in the form of the cathode and an ignitable fuel source (the anode and electrolyte). Certain defects in the manufacturing of the battery pack can result in the development of a dangerous condition called thermal runaway. If undetected, this condition can ultimately result in spontaneous combustion.

Fortunately, India has one of the world’s most stringent battery testing standards, the AIS 156.

AIS156 covers the following tests:

· Vibration test

· Thermal shock and cycling test

· Mechanical drop test for removable REESS

· Mechanical shock

· Fire resistance

· External shock circuit protection

· Overcharge protection

· Over-discharge protection

· Over-temperature protection

The test does seem comprehensive and includes all major stressors. However, these stresses are applied in isolation and are therefore not representative of actual conditions. It does not even mandate that these tests be performed on the same battery pack. OEMs can prepare a new battery pack for each test, negating the usefulness of these tests. Moreover, these are one-off tests formulated to test the design of the product and not the build quality. In order to pass these tests, OEMs often prepare samples that are usually not representative of production parts.

Testing should be designed to catch faulty products before they are shipped out to customers.

Since most battery fires are caused due to faulty cells and battery packs it would be prudent to develop an effective screening program. This can be achieved through HALT and HASS testing.

HALT stands for Highly Accelerated Life Testing and is designed to determine the lower and upper operating and destruct limits of a product. It is typically broken into 4 steps:

1. Temperature Step Stress

2. Rapid Temperature Cycling

3. Vibration Step Test

4. Combined Vibration and Temperature Cycling

Once the limits of the design are well understood, an effective screening program such as HASS can be implemented. HASS stands for Highly Accelerated Stress Screening and is used during the production phase of the product lifecycle to screen for process defects during the system or product assembly level phase.

These testing tools can very quickly identify limitations and weaknesses of the design and can significantly reduce the design process and corrective action activities for design robustness. It helps reduce development time and costs and indirectly improves product reliability and reduces warranty costs and degradation of a company's brand equity.

It is encouraging to see that Indian startups that were traditionally focused on IT and software have started to venture into the hardware space. There is a long way to go before they can catch up with China, which has been a manufacturing powerhouse for the last three decades. Indian companies should avoid the temptation of making low quality versions of western designs like China did in the 80s and 90s. To compete in the global market, the industry needs to leapfrog China by creating world-class indigenous product design centers in collaboration with global Universities. The Indian government’s "Make in India" initiative should perhaps be read as Design and Make in India.

Disclaimer: The opinions expressed within the article are solely the author’s and do not reflect the opinions and beliefs of Ola Electric Mobility or any other entities mentioned above.

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