In
Miami traffic, we were able to use the regenerative braking
exclusively.
Due to the extreme braking requirements of the race track,
we blend friction braking with regenerative braking.
The
type of driving is a big influence on how much energy is reused
through regenerative braking. Any driving that uses the brakes
more, will offer more opportunity to recover energy.
To
get an idea of the optimum effectiveness we could expect from
the regenerative braking system of the Electric Imp, we did
a series of test runs where the car would:
1)
accelerate from a stop [at a fixed current limit of 50 amps]
to around 30 MPH, then
2) immediately regenerative brake [at a fixed current also
50 amps] back to a dead stop.
The
low speed was chosen to minimize the effect of aerodynamic
drag. The test was done on a flat windless road and repeated
in both directions.
When
we totaled the Watthours out, from the battery pack accelerating
and the Watthours that went back into the battery pack, from
the regenerative braking, we recovered around 25% of the energy.
In
696 feet, 80.5 Whrs out, 22.5 Whrs back from regen, so 58
Whrs total used. Since there are 5,280 feet in a mile, the
distance was about 0.128788 of a mile. That means 625 Whrs
per mile, 450 Whrs per mile with regen.
We
might conclude erroneously that regenerative braking is only
able to capture 25% of available energy.
