Official Release: When the first production version of the BMW i3 rolls off the assembly line in Leipzig in late 2013, it will mark the provisional culmination of 40 years of development work at
BMW. It all began at the 1972 Olympic Games in Munich, where the
BMW starting line-up included two electrically powered test
vehicles. The converted BMW 1602 models served as a means of
transport for the members of the organising committee, and were
also deployed as support and camera cars in various long-distance
events. However, there could be no questioning that lead batteries
weighing 350 kilograms and with a range of around 60 kilometres (37
miles) were hardly ideal for a production car. BMW therefore
launched a series of research and development projects with the aim
of bringing an improved and, above all, more efficient technology
for electric drive systems onto the road.

From late 1975, an
experimental vehicle built on the platform of the BMW LS and fitted
with new batteries and a new electric motor started to deliver the
first findings. Then, in the 1980s, a research project was launched
entitled “Electric car with high-energy battery”, which provided
valuable experience in the use of sodium-sulphur energy storage
devices. BMW furthermore constructed a special test rig for
electric drives with a built-in output calculator. Besides the
batteries, testing here focused primarily on the drive system and
drive control. To trial the concept, eight vehicles based on the
BMW 325iX were converted and subsequently proved their merit in
inner-city use, for example as delivery vehicles for the German
postal service.

The promising results of the research project
prompted BMW to start work on designing a pure electric vehicle.
Whereas previous experimental vehicles had been merely converted
versions of standard production models, providing little scope for
tailoring them to the specific requirements of an electric drive,
this was all about to change. BMW’s work was underpinned by the
realisation that the limited range of electric cars made them of
interest for city use first and foremost. The first purpose-built
solution was unveiled at the 1991 Frankfurt Motor Show: the BMW E1,
an electrically propelled “citymobile” for use in cities and
conurbations. Even back then, this prototype stood out for its low
weight and high safety levels thanks to its consistent lightweight
design and high-strength bodyshell.

Its performance capabilities
also made impressive reading: with an output of 32 kW, a peak
torque of 150 Nm (111 lb-ft) and a range of around 160
kilometres (100 miles) its attractive key figures made it a viable
possibility for day-to-day use, too.

In addition to the five E1
prototype vehicles, the project also featured 25 converted
production models based on the BMW 3 Series. Between 1992 and 1996,
eight BMW 325 models were in service on the island of Rügen off
Germany’s Baltic coast to test out various motors, transmissions
and batteries under everyday conditions. The field trial produced
large quantities of detailed data, which provided valuable insights
for the further development of electric mobility. The project came
to a conclusion with the BMW electric in 1997.

In 2008, a fleet of
around 600 all-electric MINI E models designed for private,
everyday use took to the roads. The findings gleaned by the BMW
Group from its pilot project were channelled straight into the
development process for a production car. The potential of
lithium-ion batteries in particular was taken to new heights in the
MINI E. Just one year later, the world premiere of the BMW Concept
ActiveE in early 2010 saw the BMW Group push even further ahead
with its research and development activities. Practical trials of
over 1,000 units of this model got under way in 2011. As with the
MINI E, the overriding objective was the creation of a Megacity
Vehicle (MCV), which is now on the verge of being launched as the
BMW i3. The electric drive system in the BMW i3 Concept is a
perfect example of what ongoing, systematic development can
achieve: it takes up around 40 per cent less space than the drive
in the MINI E while generating the same output.

BMW 1602 Electric (1972)

Starting in 1969, BMW constructed two experimental vehicles
on the basis of the BMW 02 Series with the aim of investigating the
suitability of an electric drive unit for practical driving. The
place of the manual gearbox was taken by a DC shunt-wound motor
with a peak output of 32 kW that had been developed by Bosch and
whose power was directed to the rear wheels via the intermediate
gearing and prop shaft. A thermostat-controlled 140W radial fan
took care of cooling. The 85-kilogram electric motor drew its power
from 12 standard 12V lead-acid batteries from Varta, which were
positioned on a pallet in the engine bay.

The battery pack weighed
in at a hefty 350 kilograms, although it could be removed as a
single unit and replaced with a freshly charged pack. The BMW 1602
Electric accelerated from standstill to 50 km/h (31 mph) in eight
seconds and achieved a top speed of 100 km/h (62 mph). It had a
range of around 30 kilometres (19 miles) in city driving and double
that when driving at a constant 50 km/h (31 mph). For test
purposes, BMW decided to deploy the prototype vehicles at the 1972
Olympic Games in Munich, where they were used as support vehicles
for the marathon, amongst other tasks. Even back then the electric
motor doubled as a generator, allowing the energy produced during
braking to be stored in the battery (regenerative brake). It
nevertheless quickly became apparent that the specific drawbacks of
the electric drive could only be resolved by advances in the field
of battery technology. In light of this, the BMW 1602 Electric was
seen as just a first attempt at development rather than a viable
solution.

BMW 1602 Electric (1972):
Specifications
Motor

DC shunt-wound motor
(Bosch)

Continuous/peak output

12 kW / 32 kW

Energy
storage

12 lead-acid starter batteries (Varta)

Capacity

12.6 kWh

Weight

350 kg

Performance
(approx.)

Top speed

100 km/h (62 mph)

Acceleration 0-50 km/h
(31 mph)

8 sec

Range in city traffic

30 km (19
miles)

BMW LS Electric (1975)

?
In June 1975,
BMW launched a new project that was kept under wraps at the time. A
discarded BMW LS served as the basis for an experimental vehicle,
which began driving trials in December 1976. The DC shunt-wound
motor used on the BMW 1602 now gave way to a new DC series motor
from Bosch, while 10 Varta lead-acid batteries with Aquamatic
(centralised water topping up and degassing) were also meant to
provide new findings. This was the first time that the vehicle
included a charger complete with charging leads and automatic
shut-off mechanism, which allowed the batteries to be connected to
a standard mains socket and recharged in 14 hours. Although the
production vehicle’s drum brakes were retained, priority was always
given to using the electric regenerative brake first. The reduction
and differential gears were combined into a compact block and
bolted together with the electric motor. The heated windscreen and
rear window together with an electric storage heater from Bauknecht
assumed the task of interior climate control.

BMW LS Electric (1975): Specifications
Motor

DC series motor
(Bosch)

Continuous/peak output

8 kW / 17 kW

Energy
storage

10 lead-acid traction batteries (Varta)

Capacity

10.8 kWh

Weight

318 kg

Performance
(approx.)

Top speed

65 km/h (40 mph)

Acceleration 0-50 km/h
(31 mph)

11.4 sec

Range in city traffic

30 km (19
miles)

BMW 325iX (1987–1990)

?The “Electric car
with high-energy battery” research project first launched in 1981
eventually led to eight BMW 325iX models being converted from
all-wheel to front-wheel drive from 1987 onwards ready for testing.
They served as experimental vehicles for trialling a brand-new,
maintenance-free sodium-sulphur (NaS) battery, which had been
purpose-developed by Asea Brown Boveri (ABB) for use in an electric
vehicle. With an energy density three times greater than that of
conventional lead-acid batteries it represented a great leap
forward: for the first time there was a realistic prospect of
mitigating the specific disadvantages of electric drive systems,
such as battery weight and the space required. Beyond this, all of
the electric drive components were to be tested out and further
improved. BMW constructed a special test rig for this purpose with
a built-in output calculator. Another new feature was the
electronic drive management, which regulated and monitored charging
from the mains socket, the energy flow between motor and battery,
as well as the system’s thermal circuit. The entire control
electronics were housed in a compact component carrier next to the
motor. The project management team resolved to conduct the first
ever external trials under everyday conditions with the
electrically powered BMW 3 Series. A BMW 3 Series Touring proved
its suitability for daily use as a delivery vehicle for the German
postal service, for instance, while other prototype models
demonstrated their merit as city cars operated by state and local
authorities. It was not least because of this that the test
vehicles were equipped with a diesel-fuelled hot water system for
heating the vehicle interior.

BMW 325iX (1987-1990): Specifications
Motor

DC shunt-wound motor
(ABB)

Continuous/peak output

17 kW / 22 kW

Energy
storage

Sodium-sulphur high-energy battery

Capacity

22 kWh

Weight

265 kg

Performance
(approx.)

Top speed

100 km/h (62 mph)

Acceleration 0-50 km/h
(31 mph)

9 sec

Range in city traffic

150 km (93
miles)

BMW E1 and E2 (1991–1993)

?
Encouraged by
the positive results with the new NaS battery, BMW Technik GmbH was
commissioned to develop an electric vehicle from scratch, with the
objective of investigating the electric drive’s advantages and
disadvantages in practical operation. The target specifications
included performance suitable for everyday motoring, a reasonable
driving range, enough room for four adults plus luggage, and
achieving high standards of safety while keeping weight to a
minimum. After just 10 months in development, the result received
its public premiere at the 1991 Frankfurt Motor Show: the BMW E1, a
citymobile with a compact exterior measuring 3,460×1,648×1,500 mm
(lxbxh), a long wheelbase (2,325 mm) and a versatile interior. Even
now, 20 years on, many of its technical features still have a
sophisticated ring to them.

The body, for instance, was
systematically engineered to keep weight down, and featured a
high-strength bodyshell built from extruded aluminium sections and
an outer skin predominantly made from recyclable plastic. Aluminium
was used for the bonnet and boot lid. Weighing 200 kilograms, the
high-energy battery was secured in a safety frame underneath the
rear seats, while the in-house developed electric motor was
integrated in the rear axle together with the transmission. A new
electronics concept featuring two main modules ensured intelligent
control of all electrical components, whose dissipated heat was
furthermore utilised for heating the interior. The batteries were
fully recharged after just six hours when plugged into the mains
and a mere two hours when connected to a special charging station.
And with a range of up to 160 kilometres (100 miles) in city
driving, the BMW E1 also covered the catchment zone of major
metropolitan areas.

A second, more advanced version of the BMW E1
was presented at the 1993 Frankfurt Motor Show. It was equipped
with a new means of energy storage based on sodium-nickel chloride
(NaNiCl2). The “ZEBRA” battery, as it was known, was another
significant leap forward, as it helped to improve not just service
life, but driving range and performance, too. The drive system in
the BMW E1 was furthermore designed so efficiently that the energy
generated during vehicle deceleration was automatically fed back
into the battery. One year prior to this, BMW had already taken the
wraps off the E2 at the Los Angeles Auto Show. Derived from the
first-generation BMW E1, this study’s dimensions and power output
had been specially adapted to the US market. ?

BMW E1, 1st/2nd generation
(1991-1993): Specifications
Motor

Permanently excited
rotating-field
AC motor

Continuous output

32 kW

Energy
storage

Sodium-sulphur high-energy battery /
sodium-nickel chloride high-energy battery

Capacity

19.2 kWh / 19
kWh

Weight

200 kg

Performance
(approx.)

Top speed

120 km/h (75 mph) /
125 km/h (78
mph)

Acceleration 0-50 km/h (31 mph)

6 sec / 5.6 sec

Range in
city traffic

150 km (93 miles)

BMW 325 / BMW electric (1992–1997)

?
Starting in the early 1990s, the third
generation of the BMW 3 Series provided the basis for some 25
experimental vehicles, which were used for testing and honing new
components in order to gradually bring electric drive technology up
to production standard. The first generation of these prototype
vehicles included eight models that took part in the world’s
largest ever public field trial staged on the German island of
Rügen. A number of manufacturers collaborated on this joint
research project, which had the backing of the German Federal
Ministry of Research and Technology. A further six test vehicles
were incorporated into the fleet of the Bavarian State Government.
Following problems related to the sodium-sulphur batteries, in 1993
the energy storage devices were switched to the sodium-nickel
chloride batteries already familiar from the BMW E1. One BMW 325
model from the Rügen fleet was fitted with a nickel-cadmium (NiCd)
battery. Over the course of development, electric motors with
outputs of up to 45 kW were used, which now weighed just 65
kilograms including transmission. Notable progress was also made
with regard to the energy storage technology, with quick charging
now enabling the batteries to attain 75 per cent of capacity in
just 40 minutes. Finally, the engineers also succeeded in
recuperating as much as 20 per cent of the electrical energy during
driving.

The testing of the various engines, transmissions and
batteries between 1992 and 1996 produced a mass of detailed data
that provided valuable clues for further development. Consequently,
a second generation of 10 more experimental vehicles was built
between 1995 and 1997 that boasted major improvements in terms of
both performance and driving range. Sporting a striking yellow
paint finish, the “BMW electric” models were mainly used by the
technical departments at BMW.

BMW 325 / BMW electric (1992-1997):
Specifications
Motor

Permanently excited
rotating-field
AC motor

Continuous output

32 kW / 45
kW

Energy
storage

Sodium-nickel chloride high-energy
battery

Capacity

21.7 kWh / 29 kWh

Weight

260 kg /350
kg

Performance
(approx.)

Top speed

128 km/h (80 mph) /
135 km/h (84
mph)

Acceleration 0-50 km/h (31 mph)

8 sec / 6 sec

Range in
city traffic

120 km (75 miles) / 150 km (93 miles)

MINI E (since 2008)

?When the BMW Group first presented the
MINI E in 2008, it brought out a fleet of over 600 purely
electrically powered cars designed for private, everyday use. A
broad-based pilot project was launched which saw the electric car
being supplied to selected private and corporate customers, first
in the USA and then in Europe as well. The evolution of lithium-ion
batteries for automotive applications reached a whole new level in
the MINI E, with power capabilities, storage capacity and
dimensions all making impressive reading. For the first time,
customers were provided with a special charging station known as a
wall box, which allowed the energy storage devices to be fully
recharged in the space of two-and-a-half hours. The performance,
range and everyday practicality of the MINI E helped to further
boost interest in electric drive concepts and acceptance of them in
the years that followed. The findings gleaned in day-to-day driving
were evaluated and channelled directly into the development process
for production vehicles, with the BMW Group having already
committed itself to development of a Megacity Vehicle (MCV) for use
in metropolitan areas.

MINI E (2008): Specifications
Motor

Asynchronous
motor

Output

150 kW

Energy
storage

Lithium-ion battery

Capacity

35 kWh

Weight

260 kg

Performance
(approx.)

Top speed

152 km/h (94 mph)

Acceleration 0-100
km/h (62 mph)

8.5 sec

Range

250 km (155
miles)

BMW ActiveE (since 2010)

?In early 2010,
just a year or so after the debut of the MINI E, the BMW Group took
another big step towards a zero-emission production vehicle with
the world premiere of the BMW Concept ActiveE. This was because
pre-production versions of the drive components and energy storage
devices for the future Megacity Vehicle (MCV) were being trialled
in the BMW ActiveE, which was built on the basis of the BMW 1
Series Coupé. To this end, a test fleet of over 1,000 models was
dispatched into service in 2011. Delivering an output of
125 kW and maximum torque of 250 Newton metres (184
lb-ft), the BMW ActiveE sprints to 100 km/h (62 mph) from a
standing start in just nine seconds, while the newly designed
lithium-ion battery gives the vehicle a range of around
160 kilometres (100 miles) in everyday motoring. In the
meantime, the BMW Group has announced it will be marketing the MCV
via its new BMW i sub-brand from 2013. The electrical
pre-production components incorporated into the BMW ActiveE have an
identical or similar design without compromising space in the
compact BMW 1 Series Coupé. The electric motor, transmission and
power electronics have all been fully developed in house at the BMW
Group.

BMW ActiveE (2010): Specifications
Motor

Permanently excited hybrid
synchronous motor

Output

125 kW

Energy
storage

Lithium-ion battery

Capacity

32 kWh

Weight

450 kg

Performance
(approx.)

Top speed

145 km/h (90 mph)

Acceleration 0-100
km/h (62 mph)

9 sec

Range in city traffic

160 km (100
miles)

A comparison with the MINI E clearly
illustrates the technical progress made by the BMW Group in the
space of just a few years: the electric drive system in the
forthcoming BMW i3 takes up around 40 per cent less space than in
the experimental vehicle from 2008 while generating the same
output.