My current EV (Chevy S10 factory converted by US Electricar)
has pretty aggressive regen, depending on the gear selector
(the motor is fixed coupled to the wheels, so the gear selector is just
a set of switches telling the controller to adjust the drive parameters)
What I see when driving through town with this relatively heavy vehicle
(4400 lbs including driver and 2 sets of used Nissan leaf packs)
is that I use the regen braking for almost all of my stopping for
traffic lights
and slowing down for traffic and turns.
This means that most of the energy that I spent to bring the vehicle up
to speed
is put back into the battery, so the next time I accelerate, a lot of
the energy
is coming from the regen braking that I just did and only part of the
acceleration 
is taking additional energy from the battery.
All these small contributions add up, so where city driving would be
very
inefficient without regen and with lots of traffic lights and stop signs
around here,
the efficiency in city driving would be very bad (reduced range), but
instead the
vehicle is remarkable efficient because of the hundreds of times that a
small amount
of energy is put back to account for most of the subsequent withdrawal
of energy
to accelerate again, over a single charge (which lasts about 80-100
miles in my case)

This effect is confirmed looking at the gas mileage of a Prius which is
higher in city
than on the freeway, in contrast to non-hybrid vehicles, due to the
regeneration
of energy during braking, in addition to switching off the engine when
not needed.
Cor.

-----Original Message-----
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of EVDL
Administrator via EV
Sent: Monday, October 23, 2017 12:19 PM
To: Electric Vehicle Discussion List
Cc: EVDL Administrator
Subject: Re: [EVDL] Efficacy of regeneration to charge battery

On 22 Oct 2017 at 21:02, davinder via EV wrote:

> I am puzzling over how regeneration in ev charges the main battery.
> Plug in charging takes 8-10 hour charging to top up the battery - so 
> when the vehicle is rolling down hill oe deaccelerating the 'charge 
> energy' is avalable for seconds or minutes.

Regenerative braking doesn't fully charge the EV's battery.  It would be
great if it could -- drive for free! -- but it can't.  You'll never
recover 100% of the energy you used to put the vehicle in motion.
That's physics for you.  

IIRC when you add regenerative braking, the typical increase in range
(and hence energy recovery) is around 20%.  I've read that in hilly
regions you can get to 35%.  

To see this taken to an extreme, look here:

http://www.evdl.org/pages/evergreen.html

Over 20 years ago, Axel Krause of Brusa designed a light EV with
efficient components and aggressive use of regen.  He drove it over the
Apls, and thanks to the regen, got essentially the same range he would
have had if he'd driven on flat ground!

David Roden - Akron, Ohio, USA
EVDL Administrator

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