hobbit
Well-Known Member
I read through several forum threads before actually joining up, and
one thing that stood out for me was all the back-and-forth about
optimal regen-level settings and their effect on efficiency. Here
and in other similar forums, there's a lot of misinformation about
how regeneration works in the Kona, and probably Hyundai/Kia's entire
lineup of EVs and hybrids -- not to mention flat-out BS about
optimizing energy use. In the 3-ish weeks I've been driving this
I've played and learned quite a bit, and it wasn't hard to figure
out what the real story is here.
If you need a TL;dr for this, it amounts to "one-pedal driving is
stupid". That may garner enough attention to want to read the
rest of this and learn why.
Driving the Prius for a decade and a half, especially with all of
its added instrumentation, has given me a good "gut feel" for what's
happening in a driveline. It was established long since that the
second-generation Prius and everything that follows makes every
effort to stay OFF the hydraulic brakes as much and as long as
possible, duly proven out by my brake-line pressure monitors.
I don't need to add such a thing to the Kona, however, to determine
that its braking is FULLY INTEGRATED in much the same way, and that
pressing the "service brake" pedal does not throw away energy as is
so commonly feared. The Prius largely pioneered such well-integrated
braking, and it's totally a known science among all the automakers
at this point.
I had already made some satisfactory tests around home, but today I
finally got to drive a mountain-summit road up and down. [Wachusett,
as a quick experiment after *hiking* up and down, before heading
home.] On a weekday afternoon there weren't many people around, so
I was running about 25 kW in a very leisurely tool up to the top.
I was already at regen-level 0, which is my default, and on the way
down used nothing but the brake pedal to control speed. That was
showing around -20 to -30 kW as I expected, varying with the slope
as I kept a fairly even descent speed. After a while of this I
spotted a convenient pull-off and stopped, and got out to feel the
front brake rotors through the wheel slots.
Stone cold. In an ICE car, even in low gear, I would have burned
my fingertip.
Once back on the main road there was more downhill at higher speed,
and near the end of that I pulled a pretty hard stop, about as hard
as I dared with someone's pickup truck coming up behind me, to turn
off into a parking area for another check. That peaked at -75 kW
according to the yellow number on the energy display. And still,
rotors stone cold. Oh, and I got two percent SoC back, heh.
I never touched the regen paddles away from 0, and the results were
exactly as I expected. You can do this experiment yourself; find
a big downhill with a stopping place at the bottom and go to town.
Braking is fully regenerative, exactly like in the Prius, and briefly
falls back to hydraulics down around 5 or 6 mph where there isn't
enough motor speed anymore and it doesn't matter. If your rotors are
rusty after a wet night, you can feel that transition.
The integration will kick out and fall back to hydraulics under a
couple of rare situations. If you shift to N, you're completely
on hydraulics, and you can use that to clean the rust off your
rotors when needed. Heavy bumps in a strong stop will cause the
drive system to give up on regen as too hard to control under
wildly varying conditions, and some of you have probably felt that
transition once in a while -- it's very quick but perceptible in
the Kona, and probably due to today's faster processors and networks.
Bad tuning of that and some lag in the early third-generation Priuses
were one of the things that the ignorant masses were referring to as
"unintended acceleration", more properly described as momentary
braking-force fade, but they didn't learn to expect it and that the
car was simply adjusting and was not about to let them down. Also,
an outright panic stop with a fast swing of the pedal will likely go
to hydraulics first, as there isn't time to coordinate negative motor
torque between the brake controller and the power electronics. I
don't know that 100% about the Kona but it was certainly true in
the Prius, and the Kona has all the same sensors around the brake
pedal to make that work the same.
So there is no need or benefit from using any regen level other
than 0. It's pointless, and only contributes to an *inefficient*
driving style. I'm a little miffed that we can't set that as any of
the drive-mode defaults, and the OM completely lies about that. But
all I do is smack the right paddle once when taking off, and I'm set.
The 0-regen glide is beautiful, a "float" that doesn't require any
effort to lock one's foot at a particular position. In fact, there's
a tiny bit of regen in that mode anyway, but at -2 or -3 kW you can't
even feel the difference between that and Neutral. With any regen
level above that, a driver is basically always pushing a lot of
energy in and out of the pack, almost like bad ICE drivers who are
gas, brake, gas, brake, and never just coasting. Maybe having regen
recovers a little of that, but your *momentum* is the form of energy
storage that requires no conversion to be utilized for what you
want -- to jus' git on down the road! Why mess with that? Your
motor, pack, inverter, and tires will appreciate having to work
less hard overall.
More importantly in the safety context, you don't want to surprise
drivers behind you. One of the first things I've installed is a
"telltale" light for the brake lights, an LED right next to the
power/regen bargraph on the left, and yes, while very heavy regen
will cause the brake lights to come on [at whatever that NHTSA-
mandated deceleration level is that I read about someplace], you
can nonetheless regen at a level that basically makes the car fall
on its face and *doesn't* warn the people behind you. That's just
stupid, and could arguably be declared malicious if it was a factor
in an incident. Unless you're trying to collect the insurance money
from your rear-ended brandy-new EV, don't "one-pedal" in traffic.
On the highway I might occasionally use a quick shot of level 1 to
scrub off a couple of MPH and re-equalize my following distance,
but only when it's clear to the rear and I don't have to slow any
harder than that. If I slow in any significant way, I *want* the
brake lights to come on to warn those behind [at least the ones
that aren't buried in their phones].
Credit where due: "Kiwime" and David Green, at least, have also
extolled the benefits of regen-0 in other threads, and some of
that coupled with my observations today is what prompted this.
In the next post I will discuss how some of this relates to the ECO
display, because I think I've worked out what that's about too.
_H*
one thing that stood out for me was all the back-and-forth about
optimal regen-level settings and their effect on efficiency. Here
and in other similar forums, there's a lot of misinformation about
how regeneration works in the Kona, and probably Hyundai/Kia's entire
lineup of EVs and hybrids -- not to mention flat-out BS about
optimizing energy use. In the 3-ish weeks I've been driving this
I've played and learned quite a bit, and it wasn't hard to figure
out what the real story is here.
If you need a TL;dr for this, it amounts to "one-pedal driving is
stupid". That may garner enough attention to want to read the
rest of this and learn why.
Driving the Prius for a decade and a half, especially with all of
its added instrumentation, has given me a good "gut feel" for what's
happening in a driveline. It was established long since that the
second-generation Prius and everything that follows makes every
effort to stay OFF the hydraulic brakes as much and as long as
possible, duly proven out by my brake-line pressure monitors.
I don't need to add such a thing to the Kona, however, to determine
that its braking is FULLY INTEGRATED in much the same way, and that
pressing the "service brake" pedal does not throw away energy as is
so commonly feared. The Prius largely pioneered such well-integrated
braking, and it's totally a known science among all the automakers
at this point.
I had already made some satisfactory tests around home, but today I
finally got to drive a mountain-summit road up and down. [Wachusett,
as a quick experiment after *hiking* up and down, before heading
home.] On a weekday afternoon there weren't many people around, so
I was running about 25 kW in a very leisurely tool up to the top.
I was already at regen-level 0, which is my default, and on the way
down used nothing but the brake pedal to control speed. That was
showing around -20 to -30 kW as I expected, varying with the slope
as I kept a fairly even descent speed. After a while of this I
spotted a convenient pull-off and stopped, and got out to feel the
front brake rotors through the wheel slots.
Stone cold. In an ICE car, even in low gear, I would have burned
my fingertip.
Once back on the main road there was more downhill at higher speed,
and near the end of that I pulled a pretty hard stop, about as hard
as I dared with someone's pickup truck coming up behind me, to turn
off into a parking area for another check. That peaked at -75 kW
according to the yellow number on the energy display. And still,
rotors stone cold. Oh, and I got two percent SoC back, heh.
I never touched the regen paddles away from 0, and the results were
exactly as I expected. You can do this experiment yourself; find
a big downhill with a stopping place at the bottom and go to town.
Braking is fully regenerative, exactly like in the Prius, and briefly
falls back to hydraulics down around 5 or 6 mph where there isn't
enough motor speed anymore and it doesn't matter. If your rotors are
rusty after a wet night, you can feel that transition.
The integration will kick out and fall back to hydraulics under a
couple of rare situations. If you shift to N, you're completely
on hydraulics, and you can use that to clean the rust off your
rotors when needed. Heavy bumps in a strong stop will cause the
drive system to give up on regen as too hard to control under
wildly varying conditions, and some of you have probably felt that
transition once in a while -- it's very quick but perceptible in
the Kona, and probably due to today's faster processors and networks.
Bad tuning of that and some lag in the early third-generation Priuses
were one of the things that the ignorant masses were referring to as
"unintended acceleration", more properly described as momentary
braking-force fade, but they didn't learn to expect it and that the
car was simply adjusting and was not about to let them down. Also,
an outright panic stop with a fast swing of the pedal will likely go
to hydraulics first, as there isn't time to coordinate negative motor
torque between the brake controller and the power electronics. I
don't know that 100% about the Kona but it was certainly true in
the Prius, and the Kona has all the same sensors around the brake
pedal to make that work the same.
So there is no need or benefit from using any regen level other
than 0. It's pointless, and only contributes to an *inefficient*
driving style. I'm a little miffed that we can't set that as any of
the drive-mode defaults, and the OM completely lies about that. But
all I do is smack the right paddle once when taking off, and I'm set.
The 0-regen glide is beautiful, a "float" that doesn't require any
effort to lock one's foot at a particular position. In fact, there's
a tiny bit of regen in that mode anyway, but at -2 or -3 kW you can't
even feel the difference between that and Neutral. With any regen
level above that, a driver is basically always pushing a lot of
energy in and out of the pack, almost like bad ICE drivers who are
gas, brake, gas, brake, and never just coasting. Maybe having regen
recovers a little of that, but your *momentum* is the form of energy
storage that requires no conversion to be utilized for what you
want -- to jus' git on down the road! Why mess with that? Your
motor, pack, inverter, and tires will appreciate having to work
less hard overall.
More importantly in the safety context, you don't want to surprise
drivers behind you. One of the first things I've installed is a
"telltale" light for the brake lights, an LED right next to the
power/regen bargraph on the left, and yes, while very heavy regen
will cause the brake lights to come on [at whatever that NHTSA-
mandated deceleration level is that I read about someplace], you
can nonetheless regen at a level that basically makes the car fall
on its face and *doesn't* warn the people behind you. That's just
stupid, and could arguably be declared malicious if it was a factor
in an incident. Unless you're trying to collect the insurance money
from your rear-ended brandy-new EV, don't "one-pedal" in traffic.
On the highway I might occasionally use a quick shot of level 1 to
scrub off a couple of MPH and re-equalize my following distance,
but only when it's clear to the rear and I don't have to slow any
harder than that. If I slow in any significant way, I *want* the
brake lights to come on to warn those behind [at least the ones
that aren't buried in their phones].
Credit where due: "Kiwime" and David Green, at least, have also
extolled the benefits of regen-0 in other threads, and some of
that coupled with my observations today is what prompted this.
In the next post I will discuss how some of this relates to the ECO
display, because I think I've worked out what that's about too.
_H*
I like that the Kona gives us the option.
Thanks for clarifying,haven't had a chance to "test" the brake light during regen.stopping.