All-Electric: Taycan Tech

We look at the underpinnings of the new Taycan production models.

Photo: All-Electric: Taycan Tech 1
This cutaway of the Taycan shows the large floor area where the batteries go and the two motors.
October 24, 2019

In the four years since Porsche’s announcement of its 6.0 billion-euro commitment to building an all-electric car and accompanying factory, the automotive world has been in a state of flux. The European Union has been rolling out ever-stricter CO2 emissions regulations. Several European cities have announced plans for outright bans on internal combustion-engined (ICE) vehicles in city centers, with complete ICE bans being proposed. In response to this and the fallout from the infamous Volkswagen “Dieselgate” scandal, European automakers have been forced to wean themselves from the familiarity of gasoline and diesel engines and form unlikely partnerships to co-develop electric car components, such as that of VW and Ford, and BMW and Jaguar/Land Rover.

Meanwhile, in the luxury car realm, it seems that hardly a week passes without the announcement of an ultra-exclusive all-electric supercar with heady performance claims. It is against this backdrop that Porsche has spent countless hours and nearly a million miles of testing to ready the production version of its Mission E concept, known as the Taycan. After months of drip-feeding facts and pictures of specific parts of the car, the final specifications have been revealed. The following will take a look under the skin of the first of what promises to be a long line of electrified Porsches.

Powertrain

The flagship Taycan Turbo and Turbo S models are both all-wheel-drive four-door sedans with an electric motor/ inverter assembly at each axle. And yes, despite not having engines, they are still called Turbos. A future, lower-spec Taycan S version will likely be rear-motor and rear-wheel drive only.

Because no existing motors or inverters met Porsche’s demanding specifications, they were designed and built by Porsche. A pulse-controlled inverter for each motor is necessary to convert the direct current (DC) power supplied by the battery pack in to alternating current (AC) that is usable by the motor.

The front motor and single-speed transmission (with a gear reduction ratio of 8.05:1) share a common cast alloy housing, with the inverter assembly bolted atop the housing. The Turbo’s front motor output is 235 hp, while the Turbo S’s motor makes 255 hp thanks to a 600 amp inverter, versus 300A for the Turbo. Torque specs are 221 and 325 lb-ft, respectively.

The rear motor of the two Taycan Turbo models share the same basic specifications, with a 600A inverter. The Turbo S, however, is allowed a temporary “overboost” of 449 lb-ft, 43 lb-ft above the nominal output of 406 lb-ft for the rear motor when in Launch Control mode. The Turbo’s front and rear motor’s combined output is 616 hp normally and 670 hp/626 lb-ft when Launch Control and overboost are selected. For the Turbo S, it is 616 hp normally and 750 hp/774 lb-ft with Launch Control and overboost engaged.

Photo: All-Electric: Taycan Tech 2
The compact two-speed transmission for the rear motor, complete with a clutch-type limited-slip differential.

As highlighted in the Mission E feature (April 2016, #235), both motors are permanent-magnet synchronous motors (PMSM), with rare-earth magnets embedded in the rotor portion of the motor. Porsche’s PMSMs uses copper windings that are rectangular in profile and neatly arrayed in rows with 180-degree bends at each end of the stator housing. That arrangement allows a greater density of copper within the stator housing (70 percent versus 45 percent for traditional pull-in windings) while offering superior cooling ability thanks to the spacing between each strand.

The other big news of the Taycan’s powertrain is the two-speed transmission for the rear motor. This is remarkable because the broad, relatively flat torque curve of an electric motor usually obviates the need for multiple gear ratios. None of the Taycan’s BEV (Battery Electric Vehicle) competitors have more than one gear ratio. However, Porsche’s performance targets of getting the 5,100-lb sedan off the line with impressive 0-60 mph times (3.0 seconds for the Turbo and 2.6 seconds for the Turbo S) while also maintaining the time-honored German tradition of efficient, high-speed autobahn cruising meant that a second gear ratio was desirable.

To this end, Porsche devised a simple, compact two-speed gearbox that is integrated with the rear motor module. The gearbox consists of a single planetary gearset and a single actuator which controls both a dog clutch and a multi-plate clutch via two levers. For first gear, a reduction ratio of about 16:1 is achieved by the dog clutch closing and allowing the central “sun” gear to drive the planetary carrier. When the transmission shifts to second gear, a rotating drum with helically cut grooves rotates to engage the multi-plate clutch. The differential itself is an electronically-controlled multi-plate clutch-type limited-slip diff.

Battery Pack

Tesla has doubled down on its patented battery pack construction using thousands of individual cylindrical lithium-ion cells. But Porsche has chosen a more conventional route by using an array of pouch-type lithium-ion polymer cells made by Korean electronics giant LG. This is the same basic type of cell that is used in current BEVs, like the Jaguar I-PACE and Chevrolet Bolt. These pouch cells offer good energy density and cooling capabilities with excellent flexibility in terms of packaging. Each flat foil pouch cell is about 10 mm (0.4 in.) thick and contains thin layers of anode and cathode material (composed of nickel, manganese, and cobalt). The Taycan uses 396 individual cells arrayed in 33 shoebox-sized modules of 12 cells each.

Pairs of pouch cells are wired in parallel, and these pairs are in turn connected in series to provide a combined nominal voltage of 723V (actual voltage ranges from 835V when the battery pack is fully charged to 610V when discharged). This is twice the voltage level of any other BEV currently on the market and allows the high-voltage wiring to be half the diameter of that used in a 400V system, which saves space and weight. More importantly, an 800V system enables the potential for faster charging and a higher continuous motor output level because the same power level can be achieved by using half the current, which minimizes heat losses in the wiring.

Overall, the battery pack weighs 1,389 lbs, which explains the 5,132-lb Taycan Turbo’s heavier curb weight in comparison to the similarly-sized, 4,579-lb 971 Panamera Turbo. The Taycan’s battery pack is affixed to the unibody with 28 screws and is designed to be relatively easy to remove if need be. The modular battery cell design does allow individual modules to be replaced in the event of a faulty cell or group of cells.

Photo: All-Electric: Taycan Tech 3
The Taycan’s battery pack is composed of 33 modules of 12 cells each.

Cooling

Porsche’s racing experience with the 919 Hybrid was invaluable in learning the nuances of keeping the battery pack, motors, inverters, and power electronics control units at the optimum temperature. To this end, Porsche has devised a cooling system for the Taycan that is more complex than that of most BEVs. Porsche has been mum about providing specific details of the Taycan’s cooling strategies, but its basic function can be surmised by examining a diagram of the system.

The coolant radiator is mounted at the left front corner, with an air conditioning condenser at the right front, with a virtual Medusa’s nest of coolant hoses and pump modules lying between the two heat exchangers and underneath the front luggage compartment. Three coolant pumps and six switching valves are used to regulate coolant flow throughout the system. The control flow is orchestrated by a dedicated thermal management control unit, which relies on no less than ten separate coolant temperature sensors!

The coolant radiator at the left front is used exclusively for cooling the front and rear motor/inverter units. This “mid-temperature” circuit is also used to provide passive cooling to the transmissions. Battery pack cooling occurs by circulating coolant through a dedicated left-to-right cooling grid mounted between the mounting plate and frame of the pack. As is typical of EVs, the air conditioning compressor runs via the high-voltage AC system. In the Taycan, the air conditioning system is also used to help precisely control the temperature of the battery pack cooling circuit via a “chiller” heat exchanger valve mounted downstream of the air conditioning condenser.

Because the waste heat from the coolant returning from the motor/inverter cooling circuit is insufficient for rapid cabin heating and window defrosting, a third, high-temperature cooling circuit is used. This third system uses a small high-voltage electric heater grid to provide cabin heating and defrosting as necessary by circulating heated coolant through a heater core inside the HVAC box. The high-temperature coolant circuit is also used to “pre-condition” the battery pack for charging by heating it up to the optimum temperature for lithium-ion battery charging, which is about 86 degrees Fahrenheit.

Charging

Since the days of the Mission E prototype, Porsche has lauded the 800V system as a panacea in terms of battery recharging times. Of course, the ability to recharge the battery pack from 5 to 80 percent in Porsche’s claim of 22.5 minutes requires a dedicated 800V DC fast-charging station. The reason that Porsche and Tesla, among others, often quote DC fast charge times at such percentages instead of 0 to 100 percent is that fast charging is most efficient in this range. As any astute observer of the charge rate of a modern smartphone knows, lithium-ion battery packs require the charge rate to be tapered off as the state of charge approaches 100 percent, which increases battery life. Many savvy users of Tesla’s supercharger network use these stations for a quick “top-off” of range, with most charging taking place at home or the office.

All Porsche service centers will be required to have an 800V charging station for use by Taycan owners. At the time of the writing of the 2015 Mission E article, it seemed that Porsche was on its back foot in terms of the ability to implement any sort of rival to Tesla’s exclusive network of Supercharger DC fast-charging stations (now at over 1,500 stations worldwide with more than 13,000 individual Superchargers at the time of this writing).

Photo: All-Electric: Taycan Tech 4
A basic diagram of the Taycan’s three-zone cooling system.

Ironically, Porsche’s salvation in this regard has been the fallout from the VW “Dieselgate” scandal. As part of the massive legal settlement required by judges in the U.S. and Europe, VW was required to invest billions of dollars in “green” initiatives. Volkswagen used this opportunity to create its own rival network of charging stations, branded Electrify America in the U.S., and as part of a consortium in Europe with BMW, Mercedes, and Ford called IONITY. These stations feature 800V capability and charging rates of up to 350 kW via their liquid-cooled charging cables, as compared to 150 kW for most Tesla Supercharging stations, or 250 kW for the latest “V3” units. Electrify America claims it will have over 2,000 fast chargers at 500 strategically-placed stations across the U.S. by the end of 2019.

Limitations of the physical charging capability of the Porsche Taycan’s current battery pack mean that charging at such a station is limited to 270 kW by the car’s battery management system. However, Porsche claims that future variants will be able to accept charging outputs of 400-500 kW, which will truly put an 800V BEV on par with ICE cars in terms of “refueling” times. Interestingly, the standard Taycan onboard DC charger to enable charging via conventional 400V DC stations is limited to 50 kW; a 150 kW DC charger is available as an option.

Otherwise, AC charging from a standard 240V outlet with a “Level 2” charger is also possible (0-100 percent charge in about 10.5 hours at 9.6 kW) thanks to the standard AC-to-DC charger module of the Taycan. As with its existing E-Hybrid models, Porsche offers a special 240V charging dock for home installation.

Suspension & Steering

The lack of an internal combustion engine and its requisite transmission, driveshaft, and exhaust system would seemingly allow freedom in terms of suspension layout. But this was decidedly not so in the case of the Taycan. According to Ingo Albers, who oversaw the chassis development, the Taycan was the single greatest challenge that he and his team of engineers had ever faced in terms of packaging. This was due to strict governmental and insurance crash standards for BEVs and the styling team’s dedication to maintaining as many of the Mission E’s show car styling elements as possible.

The Taycan’s basic suspension shares as many components as is possible with the 971 Panamera because, within the VW Group empire, even a near-$200K BEV needs to maintain economies of scale. The double-wishbone front suspension layout of the 971 is used in the Taycan, albeit with much shorter air spring assemblies to accommodate the Taycan’s 911-like sloping front profile. The rear suspension also maintains the basic 971 layout, though the large rear motor/transmission module of the Taycan makes for tight packaging. Even if the optional rear-axle steering (RAS) system is not specified, a beam is substituted to provide the rigidity imparted by the RAS steering rack in terms of crash protection.

The initial flagship Turbo and Turbo S Taycan models are exclusively equipped with the adaptive three-chamber air suspension system from the 971, but future lower-spec models will likely be available with steel springs. The dampers feature Porsche’s familiar Porsche Active Suspension Management (PASM) system of electronically-controlled adjustment valves. The optional Porsche Dynamic Chassis Control (PDCC) active anti-roll bar system of the 971 is also carried over. The Taycan also uses the central electronic chassis platform (ECP) control unit as used in the 971 and 992 to orchestrate all of the chassis control functions.

Photo: All-Electric: Taycan Tech 5
For added strength, the Taycan features more steel in the floorpan area than the Panamera.

As mentioned in the May 2019 (#263) tech feature about tires, recent EU regulations placed strict requirements for the noise and rolling resistance of all passenger tires. Porsche is very pleased with all of the Taycan’s original-spec tires scoring a “B” rating for the rolling resistance spec, which is incredible for such sticky, high-performance tires. The Turbo features 20 × 9.0-inch front and 20 × 11.0-inch rear wheels wrapped in 245/45-R20 and 285/40-R20 tires. The Turbo S rides on 21 × 9.5 and 21 × 11.5-inch alloys shod with 265/35-ZR21 and 305/20-ZR21 rubber.

Brakes

As with most BEVs, around 90 percent of the Taycan’s braking during normal driving is regenerative braking provided by the motors. However, Porsche’s philosophy differs from that of Tesla and others in that it does not provide much regenerative braking when lifting off the accelerator pedal, so the one-pedal driving technique beloved by many BEV drivers is not possible. Porsche is adamant that the accelerator pedal is for accelerating, and the brake pedal is for braking!

Speaking of brakes, the friction brakes of the Taycan’s wheel hubs are massive! The standard Turbo rotors measure 415 mm (16.3 in.) in the front and 365 mm (14.4 in.) in the rear. The Turbo S goes even bigger with 420 mm (16.5 in.) and 410 mm (16.1 in.) front and rear. The front calipers feature ten (yes, ten!) pistons, with the rear calipers making do with four. Such a braking system was required to meet Porsche’s extremely demanding brake torture test regime that all of its cars are subjected to: 25 consecutive threshold braking events from 80 percent of the vehicle’s top speed (about 130 mph in the case of the Taycan) down to 56 mph without perceptible brake fade, all while providing between 0.80 and 0.90 G of deceleration force!

Body Construction

The Taycan features the now-typical Porsche mixture of materials and fastening techniques, with lightweight aluminum being used for all of the exterior body panels, side panels, and roof. High-strength steel is used in critical areas such as the A- and B-pillars and central tunnel. The strong central tunnel and additional aluminum-honeycomb extrusions in the rocker area combine to provide a load path between the rows of battery cells in the event of a frontal collision or rear impact, which minimizes the chance of rupturing the battery packs.

The lack of a combustion engine and its requisite exhaust system allows the Taycan to have a completely flat underbody panel, with a functional rear diffuser present to reduce aerodynamic lift. Careful attention to detail to everything from the contours of the roof panel to the sealing frames of the windshield allows a Cd figure of just 0.22 for the Taycan Turbo (at the lowest ride height with the grille shutters closed), and 0.25 for the Turbo S. This difference is solely due to the fancy powered charge port doors that come standard on the Turbo S (optional on the Turbo); the motor mechanisms partially block the “air curtain” front fender vents!

Porsche’s first all-electric production car turned out to be a technical tour de force. And this is just the beginning, as the next-gen Macan, 718s, and (likely) Porsche’s next supercar will all be electric (or at least have all-electric variants). But will the Taycan and the other electric Porsches meet the same big expectations from behind the wheel? We will find out very, very soon!

Also from Issue 269

  • 718 Spyder Drive
  • Works 718 RS 60 Drive
  • Supercharged 1988 Carrera "3.6"
  • Works 1969 917 Drive
  • Market Update: 924/944/968 & 928
  • Bicentennial 911 Turbo (930)
  • Unique Porsche Consulting Projects
Order

Also Available

2019-2020 Porsche Buyer’s Guide
$14.95 (for U.S. residents)
Can be ordered with other back issues using the Printable Order Form. Or can be purchased separately.
Connect with Excellence:   Facebook icon Twitter icon Instagram icon