One of the primary concerns related to electric vehicles have been the time-consuming charging process. The current breed of electric scooters take a dreadful 6-8 hours to recharge. This can be mainly attributed to the Lead acid batteries these vehicles have. Most lead acids can be best charged at 0.2C to ensure an acceptable pack life. That typically implies a charging time of 5-6 hours at a minimum. While any vehicle will be parked for more than 6 hours in the night, such a ‘re-fueling’ requirement is a step-back from what vehicles can do today. An ‘overnight’ charging requirement imposes a steep psychological barrier for any user and today, arguably, is the single biggest deterrent to their large-scale adoption.
For electric vehicles to be mainstream, we need faster charging. We must appreciate however that the charging problem is as much a chemistry problem as a charger issue. With most current chemistries of lithium-ion, a sub-one hour charging time is achievable.
Having a lead acid battery is like having a small straw connecting your water tank and pump, there is only so much of water you can pump when your pipe is so small. Having Li-ion battery is like replacing the straw with a big water pipe. Now, how fast you can fill the tank depends on how powerful is your pump.
It is the charger’s job, to juice in the power from the electrical sockets in your homes/offices and supply it to the batteries. For electric two wheelers in general, power availability is not a problem. So at this stage it’s down to the capability of the charger itself.
But a lot of design factors which could be neglected for a 250W charger, used by most electric scooters, can become a big nuisance for a fast charger which is 10X more powerful. There is a lot more heat, lot more complexities and a lot more cost. The necessity of an on-board charger makes size and weight as critical factors too. Hence an ideal fast charger for a scooter will have 4X the power density of the current chargers, will not cost a fortune and yet supplies the required power with optimum efficiency.
A deeper-dive into the technology of charger
Electric vehicles are here for the long term and eventually there will be a few million of them on our roads. Imagine a scenario where all the vehicles are charged simultaneously.
Most current chargers introduce some noise into the grid during operation and at higher power levels and with a higher number of vehicles, this noise has the potential to collapse the grid. Additionally, the electromagnetic interference (EMI) caused by the chargers can also be a significant issue for nearby electronic devices. By introducing power factor correction and filter circuits between the grid and the charger, we can ensure that the grid remains isolated from any such noise and prevent any EMI issues also.
Chargers are fundamentally a power supply unit. And like all power supply units they have transformers and inductors which work at a specific frequency. This frequency majorly dictates the volume and the weight of the charger. Now, the current generation of electric scooters in the country come with chargers which work at sub-100 kHz frequency. To build a charger which has 10X the power in the same volume we need to work at a frequency which is at least 4-5X.
It’s of course not as simple as just selecting a micro-controller which works at higher frequencies. A higher frequency impacts the choice of components, affects the PCB design and has the potential to significantly increase the system losses. And when you are working at say 2.4kW, even a 10% loss is more power than currently what the entire electric scooters needs to run!
The way to solve these problems is by utilizing topologies which enable zero voltage switching, introducing high efficiency components like silicon carbide diodes and thermal designs which can dissipate several hundred watts of heat without failing.
We are working towards designing and building a versatile fast charger that can meet all the mentioned requisites and can also overcome the associated challenges. And with Ather’s approach of vertical integration we are able to cut down on redundancies in any system. Overlapping features get eliminated, packaging improves, costs go down and the end product is a much more cleaner and intuitive experience.
One of the big thesis that we believe in is that vehicles of the future will be smarter and connected. The coming decade for vehicles will be defined by this new vertical. In such a scenario it is vital that all components reflect that idea. Our chargers interact with the rest of the systems, understand your usage, will learn from you and improve your overall experience over time. This will enable for detailed monitoring, control of charging parameters and with regular software updates, effectively improve the charger every month.
All this has been possible because of a very dedicated and innovative team which has the attitude of challenging the status quo and is devoted to giving our riders a WOW experience.
Stay tuned for more updates!