According to Mark Ellis, Munro & Associates battery specialist, Tesla has a state of the art battery pack. Its management system is years ahead of what competitors currently offer. When we described the Obrist Mark II, their vacuum fixation technology called our attention. Why was it so revolutionary as the Austrian company described it? We spoke to Martin Graz, COO of Obrist Powertrain, and it all resumes to its cost and weight goals: both as low as possible.
Gallery: Worst Tesla Ever? Obrist Mark II Is A Different Proposition For EVs
As we explained, the Mark II did not have the objective to be better than the Tesla Model 3. The fact that they look similar is just a detail. The Mark II’s goal is to show that the HyperHybrid system can offer a car that can run 1,500 km with 30 liters of gas or a little less with renewable fuels. It also happens to cost less than half of what the Model 3 price – in part, due to the vacuum fixation technology.
It has an important role in keeping costs down and also in improving the energy density of the pack. That is probably the most surprising part of the whole concept. Check what Graz told us.
“We use 18650 cells. They are a commodity, so we do not care too much about them, but rather about thermal management. We take care of the cooling and the assembly process. To increase the energy density of the battery pack, we have conceived the vacuum fixation technology. Think of ground coffee. That is more or less the same process, only with cells.
The internal components of a battery pack need extruded material to hold them together. Then it needs insulation, a case, more components and all that increases the weight. It is a time, space and money consuming process. A regular battery pack case has 6-mm thick aluminum walls. Ours is a third of that, only 2 mm thick. It’s cheaper and lighter. And the vacuum keeps the components still at a low cost.”
If you did not see where Graz is heading, here is how the solution increased the battery pack’s energy density.
“When people calculate that, they include everything that composes the battery pack, not only the cells. The heavier this is, the less energy-dense the packs also are. With our vacuum fixation solution, we reduce the battery pack weight.”
Being lighter does not make it a fragile solution, according to Graz.
“Again, remember the ground coffee in a vacuum pack. That is really solid. The same happens with our battery pack, which presents an extremely rigid structure.”
The video above mentions air or liquid cooling for the pack, but have no doubts: The Mark II uses the second option.
“We have both options, but, for the Mark II, we go with water cooling. It is under all conditions the better option, but, with parallel hybrids, you need it. They face extremely high C rates under acceleration.
When you have a vehicle with a 100 kW motor and a 100 kWh battery pack, there is a relatively low discharge demand rate: only 1 C. On the other hand, you have a 600 kg battery pack.
If you have an 85 kW motor and an 8.5 kWh battery pack, that is 10 C, which increases the cooling needs dramatically, but you have a small battery with low weight. Only the liquid cooling can deal with that in an adequate way.”
You may have noticed the Mark II has a sort of grille where the Model 3 has C-pillar windows. That has nothing to do with the cooling.
“We have to make totally clear that this is a demonstrator vehicle for legal reasons, hence these changes. They are merely to distinguish the Model 3 from the Obrist Mark II.”