How does Porsche's Ultra-fast 800V EV charging work? | Taycan's Battery Architecture

Being used to fuelling cars in under 15 minutes for a 400 km range, it’s natural that every driver expects the same to happen with electric cars too. However, is it technically feasible?

A few days before, Porsche and BMW answered with a big YES, by demonstrating an ultra-fast charging that could charge 400 km range in about just 15 minutes. The Porsche test vehicle had a 90kWh battery, and the station was able to charge it at a rate of over 400kWh. BMW test was at i3 with a 57kWh battery, that car charged to 80% capacity in 15-minutes.

Here’s how they achieved the feat, as far as I understood. The magic is not just on the charging part, but is on the combined efforts of Porsche & BMW’s excellent battery architecture, Siemens grid connection, Phoenix contacts’ cooled charging cable, along with Allego’s super charger.

Most of today’s DC fast charging stations work on about 400V. With a typical charging power of 50KWh (400V * 125A), these chargers would take approximately 80 minutes to charge a 65KWh battery that can run for 400 km range (assuming an average efficiency of 16.25 kWh/100 km).

Even the newer 400A high current grid connections would provide only a max 160 KW (400V * 400A), which is not sufficient for Porsche to achieve over their Ultra-fast charging goal. So, Porsche decided to double the voltage - not on the grid connection, but intelligently on the battery charging side.

Any EV’s battery pack voltage is a result of how the individual cells are configured into parallel groups and how those groups are connected in series. Individual lithium-ion cells are typically only about 3.6V but when looped one cell to the next e voltage adds up. Typically, around 108 cells are laced together like this (picture below) to get a total nominal battery pack voltage ranging from around 350 to 400 volts.

The Porsche charging system uses the Combined Charging System (CCS) connector and can split its 800V throughput into two 400V plugs. When doubling the voltage, we can achieve up to 320KWh (800V * 400A). On top of it, the use of cooled charging plugs increases the charging current further to the extent that it can go upto 450KWh.

This is indeed a great engineering achievement; however it is still in a research stage (PoC). Even if the ultra-fast charging becomes ubiquitous, next-generation batteries and grids will need an extensive and expensive upgrade to take the "full" advantage of this advanced technology.

Up for debate is: whether the required infrastructure investment and more-robust batteries even will be worth it!. I strongly feel that, the EVs, even in long-term would only aim for optimizing their battery cells density tuned for "modest" charging rates and "low cost". What do you think?