I think it was the 9th of August of last year (2022), we opened our rounds of discussions internally, “Now that our Platform Zero is ready, we need to test the hell out of it!” But taking it on the roads was not feasible. It was all bare shell, good for, maybe, off-roading, as it was equipped with seatbelts, helmets, and such! After much deliberation, we concluded that the only option we had was to integrate our platform into a legally drivable vehicle. This posed a challenge as none of the trucks on the road had the electrical and sensor system we wanted to test. It has to be a car – something heavy to represent a small truck and capable of carrying an extra ton of batteries. Which car could meet our requirements? Mercedes Benz S Class!! 😅
We chose the S-Class for multiple reasons. Its parts are easily accessible, it has ample boot space for our batteries, and its air suspension would provide necessary protection for our batteries and connections. Already weighing over 2 tons, it could handle an additional 800 kilograms, making it a suitable choice for a small-scale test of our 55-ton dream! However, everyone we consulted, said, it couldn’t be done!
The integration process was deemed too complex due to the car’s intricate electronic control unit (ECU) that governs all its functions, along with 100s of other microcontrollers. If we couldn’t get the ECU to work, even the doors wouldn’t open. Despite the skepticism, we managed to hack it and get it on the road in less than three months of consistent effort! Having said that, S-Class is one of the best-designed automobile vehicles out there and our engineers were in awe while seeing the inner workings of this beast!
Surprisingly, the S-Class seemed to be designed for electrification. After removing the engine, the engine bay area provided a perfect space to accommodate all the electrical and electronic components. The spot where the driveshaft meets the engine was seemingly designed to fit our axial flux motor! It almost felt like the car was designed in 2009 specifically for ours to electrify it!
On 12th August, we dismantled the engine-bay area, removing the engine and any unnecessary components, totaling approximately 350 kilograms. Ensuring the suspension worked, especially the rear one that would bear the weight of the battery, required some hacking, but we eventually succeeded! The boot space was spacious enough to house almost all of our battery modules, resulting in a 40kWh battery pack operating at ~800 volts.
Once we removed the engine, we created a mechanical two-tier cage system in the engine bay area to accommodate our power distribution units (PDUs), charging system, inverter, and other components. It involved some clever hacking to gain access to the car and bypass various systems (SP Road in Bangalore has some of the country’s best German car hackers, and we commend them for their skills!). Once our vehicle control unit (VCU) was plugged in, everything worked perfectly (except for the annoying “flat tire” indicator). Excited to test it out, we hit the road but immediately encountered two major issues!
Firstly, the power steering was not functioning because the power steering compressor relied on the engine we removed. There was nothing powering the pump! Secondly, the car wouldn’t go above 30 kmph, and the power system would shut off as soon as we accelerated enthusiastically. It was the time to go into debugging mode!
The power steering issue was expected since the power steering pump was no longer present (in the original configuration, it was driven by the engine). The speed limitation and power cut-off seemed related. Upon inspecting the software, we discovered that we had limited the torque to 200Nm and the RPM to 2000 (never needed more with Platform Zero’s limited tests).
Ironically, we were operating out of a basement and needed around 1300Nm of torque to drive the car up a steep ramp, and we were getting 530 Nm of torque on the wheel shaft (200Nm from motors and 2.65 scaleups from Benz’s rear differential). Had we not wished to drive outside under the sun, we wouldn’t have decided to electrify a car and would be sitting happily with Platform Zero’s performance. Fixing the software issue was relatively straightforward, but when we reached 50 kmph, the coupler broke due to the insane power of our axial flux motor and a manufacturing defect. Our coupler’s (the thing connecting the motor and the drive shaft) bonding between the metal sleeves and rubber just gave up. It took us 3-4 days to manufacture a much better coupler made of steel-infused rubber, which provided a more reliable connection between the motor and the driveshaft.
Power steering presented a greater challenge. Most of the electrical and hydraulic circuits were intact, but we needed a motor to run the pump. They say that if you look hard enough, you can find God! And so, we looked hard and found the Mahindra eVerito! The eVerito featured an electro-hydraulic pump that was CAN-based, and we came across some YouTube videos on how to bypass some of its restrictions. Our engineers went to work, and within a week, we successfully integrated it into our system.
The next day, on the 28th of October, we took the car out for a drive. It was a truly magical experience! In hindsight, it felt like, how the Mercedes F1 team must be feeling after achieving a double podium at the just concluded Spanish Grand Prix. Against all odds, we had successfully electrified the S-Class. Every member of our team worked like a magician during those three months (and continues to do so today)! On the road, our system didn’t disappoint the Benz. The acceleration was as quick as the original, and although we were limited by the RPM since we didn’t use a gearbox, we reached a maximum speed of 105 kmph, with the motor shaft directly connected to the Mercedes differential with a ratio of 2.65. I think we can easily touch 250kmph, but we’ll only learn about it in 2025!
I consider myself blessed to have such an amazing team at Tresa, where everyone is passionate and takes ownership of the project. They are determined and truly believe in what we do, and, most importantly, that it can be accomplished. While we receive many inbound requests to join our team, finding the right culture fit is more important to us than anything else. Here’s a small tribute to our engineers who worked tirelessly day and night to make this second step possible back in August-October 2022.
Having successfully electrified the S-Class, we gained confidence and set our sights on building the truck! However, we proceed in small steps. So, stay tuned for next week’s update, where you get to delve into how we created our first electrified truck chassis and the valuable lessons we learned along the way.