Legacy of the Porsche 356

In the aftermath of World War II, many car manufacturers, especially European ones, experimented with the relatively less expensive roadster or spyder configuration: a topless two-seater sports car. Ferry Porsche, son of pioneering automotive engineer Ferdinand Porsche, developed a sports car based on VW parts in 1947-48 that is generally considered to be the “grandfather” of the 356 Porsche Speedster.

1948 Porsche 356 prototype, the grandfather of the Speedster (courtesy of Cartype)

The 1948 prototype, sequentially the 356th design concept of the small entrepreneurial team, was introduced in 1948 as the Porsche 356. From the beginning, the Porsche featured an engine mounted just in front of the rear axle that, some sixty years later, is well suited to an electric motor.

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What's an electric replica?

In general, a replica is a reproduction of a vintage or esoteric vehicle at a price point well under what the original might be worth. Replicas can be either professionally assembled or sold in kit form for home builders. Often a replica of a vintage car will substitute current technology for old components, especially where safety or sourcing issues arise.

Sports Car Illustrated advertisement for
Castrol oil featuring the Porsche 356 Speedster

Many kit cars are based on donor vehicles so that a relatively inexpensive chassis and power plant can support a new replica body, often made of fiberglass. Factory Five Racing, for example, exclusively used a Ford Mustang donor prior to 2007 for their popular AC Cobra replica. 

Inexpensive replica kits may offer not much more than an unpainted fiberglass body that fits over an existing chassis. In the past few years, non-donor kit car builds have risen in popularity as aftermarket components and crate engines have become more widely available.

An electric replica is a further evolutionary step from the original vintage vehicle where the gas-powered internal combustion engine is replaced with an electric motor and battery pack.

The sports car described on this site is a electric replica of a 1957 Porsche 356 Speedster assembled using a chassis and fiberglass body manufactured by Special Editions, Inc. under the trade name Beck Speedster®. The electric system design and battery pack configuration is based upon the pioneering work of Jack Rickard and Brian Noto of EVTV.

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Battery evolution

Benjamin Franklin, as part of his well-known exploration of electricity in 1747, was the first to group together a number of jars into what he described as a “battery”, using the analogy of military weapons coordinated for a powerful offensive. These jars, developed in 1745-47 by scientist Pieter van Musschenbroeck of the University of Leyden, Netherlands, could collect an electrical charge between two metal plates.

Franklin found that by multiplying the number of holding vessels, a stronger charge could be stored, and thus more power would be available on discharge, a fundamental concept behind battery cell architecture. Franklin's battery, however, was actually what we refer to today as a capacitor.

Franklin called his Leyden jars a "battery" (Photo by Peter Harholdt, 2004, courtest of Franklin & Marshall College)

The first “real” battery, in the modern electrochemical sense of the term, was invented by Alessandro Volta in 1791; the volt, the unit of electrical potential, is so named in his honor.

In 1859, Gaston Planté invented the first rechargeable battery, the familiar lead-acid chemistry still in use to start an internal combustion engine. Rechargeable technology progressed slowly over the next 150 years, with a handful of important milestones:

• 1899: nickel-cadmium battery introduced
• 1903: building on the nickel-cadmium heritage, Thomas Edison develops a nickel-iron battery to power early electric cars
• 1912: G.N. Lewis experiments with first lithium-based battery chemistry
• 1991: first commercial lithium battery produced based on research by John B. Goodenough
• 1996: Goodenough and coworkers identify potential of lithium iron phosphate (LiFePO4) as cathode material
• 2002: Yet-Ming Chiang and MIT coworkers demonstrate lithium performance enhancements from chemical doping
• 2007: early prototype LiFePO4 battery used in vehicles as demonstration projects
• 2008: Mitsubishi and GS Yuasa establish Lithium Energy Japan to manufacture large format LiFePO4 battery cells
• 2009: price of EV-suitable lithium batteries drops significantly to under $400/kWh, a level that makes DIY lithium cars practical
• 2011: Winston Chung, the founder of Thundersky, leaves in a legal dispute involving 15 LiFePO4-related patents and forms Winston Battery; Thundersky is renamed Sinopoly.

Today, the era of LiFePO4 battery chemistry is just underway. New Chinese manufacturers, like Winston, Sinopoly, and CALB (China Aviation Lithium Battery Company) are producing large format, relatively inexpensive cells that are available in small lots to kit builders and converters. Wholesale prices are now approximately $1.00 per amp-hour ($280-300/kWh equivalent).

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Lithum versus gasoline 356

How does a new lithium battery electric 356 compare to the vintage 1957 gas-powered Porsche original?

Apart from the obvious lack of engine noise, tailpipe, and gas cap, the two sports cars have similar handling characteristics.

The following table compares a number of key specifications, including power, energy storage, and performance measures.  See footnotes for details about conversions.

SPECIFICATION	LITHIUM 356	GASOLINE 356
Power system
Type	AC electric motor	air-cooled engine
Power [1]	57 kW	52 kW
Useful RPM maximum	6,500	6,000
Expected powertrain life	385,000 miles [5]	100,000 miles
Transaxle final gear ratio	3.88 to 1	4.42 to 1
Energy storage
Capacity [2]	24.5 kWh	490.0 kWh
Weight (fuel or battery)	445 lbs	90 lbs [3]
Energy density	109 Wh/kg	12,200 Wh/kg [4]
Storage form	36 LiFePO4 cells	13.8 gallon fuel tank
Performance
Top speed [7]	110 mph	110 mph
Range	140 miles	270 miles
Efficiency [6]
Miles per gallon [9]	215 equivalent	20
Cost per 10,000 miles [8]	$186	$2,000

FOOTNOTES
  1. gas: based on 70 bph of the 1582cc overhead cam flat-four Porsche engine at 4500 rpm
      lithium: based on 4th gear at 4200 rpm
  2. gas: based on fuel tank capacity
      lithium: based on 3.4 voltage and 200 Ah capacity of LiFePO4 cell
  3. based on average gasoline weight per gallon
  4. based on average energy density of gasoline
  5. calculated using 70% DOD specification of minimum recharges
  6. calculated using average U.S. residential electricity rate of $.11/kWh and $4/gal, average ICE Speedster mpg
  7. effective maximum speed based on chassis, suspension, and body air resistance
  8. based on average full charge cost of $2.70, 145 mile max range, yielding $0.0186 per mile cost
  9. equivalent calculated using average $4/gal premium gasoline versus $0.0186/mile electric cost

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