Ifirst converted a car to purely
electric operation in 1999 and
after several improvements —
particularly to the battery pack — the
car was moderately successful. I was
generally able to travel about 50
miles on a charge and considerably
more if care was taken. The car
completed the London to Brighton
Electric Vehicle (EV) Run in 2005
Unfortunately, the achilles heel of
the EV is still the battery pack. With
motor can take the car only about
one mile at less than 31 mph.
I wanted to reduce the fuel
consumption of the Prius from 60
mpg to 100 mpg — a massive cost
savings — by the addition of a large
Li-Ion pack. This article described
how I achieved this using E-blocks
and Flowcode from Matrix
Multimedia as a control system.
How It Works
■FIGURE 1. The basic topology
of the Prius drive system.
low cost, traditionally lead-acid
batteries the range is severely limited
and a long, cross-country run must
be planned like a military campaign.
There must be charging points every
50 miles or so, and you need to stop
for a couple of hours at each to
restore some charge.
In 2005, I started looking at the
hybrid cars that were available and
the Toyota Prius in particular. The
interesting thing about the Prius
was that it could run for a limited
period as an EV, however with the
NiMH battery pack the electric
Figure 1 shows how the Toyota
Prius works. Essentially, it is a normal
car with the addition of an electric
motor/generator in the drive train.
When the driver needs to slow down,
the brake pedal puts the ‘motor’ into
generator mode which charges the
battery up. Conversely, at low speeds
the motor is used to assist the
conventional petrol engine which
decreases fuel consumption.
When I started the project, a few
groups in the US were experimenting
with supplementary battery packs to
increase the range of the Prius. The
Toyota — along with most modern
cars — has a very complex electronic
control system. The part that deals
with drive and battery management
uses CANbus for communication.
The operation of the drive among