On 06 Jun 2021 21:16:30 +0100 (BST), Theo
wrote:

Tim+ wrote:
T i m wrote:
I would be interested to hear from Theo below what speed the breaking
is still mostly mechanical (re urban / motorway driving).

I think you mean “braking”. I can’t speak for hybrids but on EVs there is
no “speed limit” for regenerative braking. The limits are the rate of
deceleration that the motor can produce and the battery capacity. A fully
charged EV won’t do regenerative braking as there’s simply nowhere to put
the energy.

I think gen2 Prius regen goes down to about 7-8mph.

That's lower than I thought but that said, I know all too well how
'heavy' a shorted electric motor can become when trying to push a
mobility scooter. ;-)

At that point the
amount of braking you can get from the motor alone is limited, and you want
it to stop accurately (going 1 metre extra across a pedestrian crossing
would not be great).

So it *will* actually bring you to a halt with motor braking alone,
noticeable above rolling resistance etc?

You can feel it's a bit notchy slightly above that
speed - as if you can feel the poles of the motor as it rotates - which
is a bit disconcerting until you get used to it. Your instinctive reaction
is to push the brakes harder which will bring in friction braking anyway.

Makes sense.

Unless you're descending hills, on the flat it will keep some headroom in
the battery such that there's enough space to capture energy in regen.

So what does it do when descending hills, assuming you approach the
top of one with a fully charged battery? Two questions really:

Does it 'coast' if you don't touch the brake like a car in neutral or
'hang' on the motor / transmission like one in gear but with you foot
off the throttle?

What if you apply some (electric) brake that would maintain the same
speed but then make the battery fully charged (either really or
technically), does it then apply the mechanical brakes on it's own
(like an ABS) 'instead' or start coasting faster till you use
mechanical brakes?

It'll then use that energy next time you accelerate, so it tries to always
have scope to regen. Although the motor isn't large, so if you're less than
gentle on the brakes it'll bring in the friction system.

The motors on the mobility scooters we have seem quite large (by
comparison then) and the big one will bring it and me to a halt from
full speed (8mph) down a fairly steep slope in a bit over a second.
;-)

Cheers, T i m