Electric cars with 800 volts: more efficiency thanks to higher voltage

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The Hyundai Motor Group has done a convincing job with the e-GMP platform: Electric cars with an 800 volt voltage level in the traction battery are the benchmark. Hyundai Ioniq 6, Kia EV9 and Genesis GV70 (test) are striking examples of the potential of the e-GMP. But what's the point - why are there more and more electric cars with 800 volts? Is charging power really the most important distinguishing feature? If Hyundai in the Kona or Tesla in the Model Y continue to rely on 400 volts, are these electric cars automatically inferior as a result? As is so often the case, it depends more on what the manufacturers make of it.

More and more electric cars with 800 volts

First of all, it is obvious that the industry is increasingly offering electric cars with an 800 volt voltage level. The Porsche Taycan (test) made the start in 2019. The Audi e-tron GT shares the technical basis called J1. It was and is impressive when 270 kW peak power can be read at the charging station. However, the wealthy customers of Porsche and Audi are still waiting for the further development of the J1 platform. The Premium Platform Electric (PPE) will be used in the Macan, the Audi Q6 e-tron and e-tron Sportback as well as the Audi A6 e-tron and e-tron Avant. The launch has been delayed several times. Exactly why is not transparent.

BMW wants to overtake Tesla in 2025

BMW announces the introduction of an 800-volt system for the "New Class" electric car models. Round cells with a diameter of 46  millimetres and in two different heights from the supplier EVE will be delivered from 2025: First comes the iX3 (NA05) with 120 millimeter high cells. This will be followed by the i3 sedan (NA0) with a height of 95 millimetres. BMW Board Member for Production Milan Nedeljkovic believes that Tesla will fall behind when the New Class models appear.

Meanwhile, Tesla has introduced the Cybertruck, the first electric car with an 800 volt voltage level for the traction battery. For Model Y and Model 3, it will remain at 400 volts, at least for the time being. There is an increase elsewhere: all Teslas will soon benefit from an increase in voltage from 12 to 48 volts in the traditional vehicle electrical system - a remarkable change. The vehicle electrical system supplies the headlights and infotainment devices, for example.

Will the facelift bring 800 volts to Mercedes?

Mercedes is introducing the 800-volt traction battery with the next CLA, whose concept study caused a stir at the IAA 2023 in Munich. Mercedes promises a time of less than 20 minutes for the typical charging stroke from ten to 80 percent. That is roughly as fast as the e-GMP from Hyundai, for which the factory specification is 18 minutes.

It is also not ruled out that Mercedes will switch from 400 to 800 volts for the EQE and EQS as part of a revision - known in brand jargon as "Mopf" (for model upgrade). In summary, it can be said that the introduction will begin in high-priced vehicle classes and gradually continue downwards. The boundary currently lies between the C and D segments, i.e. in simple terms between the Hyundai Kona (test) and Ioniq.

More insulation effort

So the whole thing must have something to do with money. On the one hand, the costs arise because a higher voltage has to be better insulated. On the other hand, and this is the more relevant part, there were no standardized 400-volt components such as air conditioning compressors at the beginning. The power electronics for 800-volt systems had to be newly developed. The Hyundai Motor Group made the investments and can now comfortably watch them pay off. Battery systems with different voltage levels do not have a different energy content. A Hyundai Ioniq 5 starts with 58 kWh. A VW ID.3 has just as much, although there are no indications from Wolfsburg that the modular electrification toolkit (MEB) will be changed from 400 to 800 volts.

Smaller cable cross-section, less power loss

What is different, however, is the wiring of the cells in the system. If you change from 4p3s (i.e. four cells in parallel and three such packs in series) to 2p6s (i.e. two cells in parallel and six of these units in series), the voltage doubles with the same number of cells. At the same time, the current is halved according to the physical relationship "power equals voltage times current", or P=U*I for short. The power loss at the connecting cables increases quadratically with the current. By increasing the voltage from 400 to 800 volts, it would fall to a quarter with an unchanged cable cross-section. If the cable cross-section is reduced, the power loss only increases in linear proportion to this reduction. The conductor cross-section of the copper cables can therefore be reduced. The core of the matter is therefore internal efficiency.

An additional positive effect is that copper cables with a smaller cross-section have a smaller bending radius. In a battery with 800 instead of 400 volts, the cells can be joined closer together. At the same time, the weight decreases slightly because less copper is required. The energy density increases. The effect is best known at the DC charging station: electric cars with 400 volts are limited to a maximum output of 200 kW if the cable transmits 500 amps. At 800 volts, this is theoretically 400 kW. But not in practice.

Tesla is just as fast

It would be a fallacy to assume that electric cars with 400 volts necessarily charge slowly. The benchmark is the C-rate, which translates into the usual time it takes to charge from ten to 80 percent. As mentioned, Hyundai's e-GMP is the benchmark at 18 minutes. In a comparative test, the Norwegian Youtuber Björn Nyland soberly states that a Tesla Model Y with LFP cells from BYD reaches 80 percent just as quickly as a Hyundai Ioniq 6. At the same time, the Model Y dominates the BYD Atto 3, although presumably very similar cells are installed: When the Tesla is at 80 percent, the Atto 3 is at just over 50 percent.

Know-how in the management software

Translated: The Tesla Model Y (test) has a de facto charging power limit of 200 kW. However, the Hyundai Ioniq 6 cannot exploit the potential of the 800-volt system. The reason for this most probably lies in the control of the cells themselves. It makes no difference to the individual cell how it is connected. More important are the properties of the cell chemistry, the management software and the heating and cooling system. Perhaps Tesla simply beats the LFP cells a little more intensively because they are fundamentally less sensitive than NMC cells. One thing is clear: Tesla has a great deal of expertise in cell control.

Complex heating and cooling systems for 4C and more

So when the automotive industry announces electric cars with 4C or 5C for the second half of the decade - i.e. with a waiting time of a good ten or even less minutes to get from ten to 80 percent - a higher voltage level is not the inevitable or exclusive prerequisite for this. More important are the cell chemistry, the battery management software and the heating and cooling system of the traction battery.

Not always more economical

It is also not the case that electric cars with a voltage level of 800 instead of 400 volts are always more economical. A Hyundai Ioniq 5 (test), for example, has relatively unfavorable aerodynamics and consumes a comparatively large amount of electricity. The technically largely identical Ioniq 6 (test) shows how things can be done much better. It is the overall package that counts, not individual components. In the medium term, the number of electric cars with 800 volt traction batteries will increase significantly. Suppliers will increasingly design their parts for this and costs will fall. The fact that copper requirements are lower at the same time will be relevant in view of the mass ramp-up. Against this backdrop, the introduction of Tesla's 48-volt instead of 12-volt electrical system is also extremely interesting - not all new cars are electric, but they all have an electrical system.

(vza)