JoeS
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Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: Regen vs Neutral and speed for max range

Thu May 04, 2017 8:39 am

Aerowhatt, thank you for the excellent and very logical suggestions, especially the one driving in Eco which reduces the pedal sensitivity. I'm pretty tied up for the next couple of days but will attempt to do this every time I go to town.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

JoeS
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Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: Regen vs Neutral and speed for max range

Fri May 05, 2017 10:49 am

Brief update: using SoC over this short stretch doesn't work, as both CaniOn and EVBatMon only show a 0.5% resolution, which doesn't change over the course of this downhill, using either technique.

Will keep trying to see if Wh/km is doable, as controlling the amount of energy going into the car during acceleration is difficult/unmeasurable?, as is keeping a steady foot on the accelerator.

Science Saved Me A Ticket. Good thing I was going slow doing this testing, as yesterday there was a barely-visible Sheriff standing in the shadows with a handheld laser gun point up that final downstretch...
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Aerowhatt
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Joined: Wed Jan 28, 2015 1:52 pm

Re: Regen vs Neutral and speed for max range

Fri May 05, 2017 1:59 pm

JoeS wrote:Brief update: using SoC over this short stretch doesn't work, as both CaniOn and EVBatMon only show a 0.5% resolution, which doesn't change over the course of this downhill, using either technique.

Will keep trying to see if Wh/km is doable, as controlling the amount of energy going into the car during acceleration is difficult/unmeasurable?, as is keeping a steady foot on the accelerator.

Science Saved Me A Ticket. Good thing I was going slow doing this testing, as yesterday there was a barely-visible Sheriff standing in the shadows with a handheld laser gun point up that final downstretch...


I was afraid of that. It's a pretty short road at only 1.3 miles. Wh/km should be able to show up a difference even on a short hop. That's what's nice about my "mostly" descent, it's 27 to 34 miles long depending on the chosen starting point. Sections that I look hard at because of their consistency of conditions are 5 miles or more each. Problem is I can't test it at 35 mph. The speed limits for the most part are 45 to 65 mph. Drivers around here tend to add at least 5 mph to that. Just not a safe option to go slower!

I did a little refresher on aerodynamic drag while waiting in stopped traffic today. Comparing 7,500 ft elevation to sea level. Air density
is a nice round 80% of sea level at 7,500ft (the averaged altitude of my journey). Since air density is a single multiplier in the drag equation it gets simple. Basically, given the same velocity one would be fighting 80% of the resistance that they would be at sea level.

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

JoeS
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Re: Regen vs Neutral and speed for max range

Thu May 18, 2017 9:25 pm

Aerowhatt, thanks for doing the drag comparison. Hey, the only reason for this whole discussion is the aerodynamic drag effect!

Well, I've been totally unsuccessful in trying to get any meaningful data by trying to keep the accelerator in a constant position and a constant speed. The combination of curvy and undulating road, short distance, and slow speed makes it not doable, IMO. On this stretch, it is soooo much easier to just kick the car into Neutral and not worry about it. For maximizing range, this low speed test doesn't address the comparison we're trying for, anyway. Neutral gives me a steady-state current draw of 1.3A (correction, I had written 1.8A) at around 50%SoC.

During my recent Tesla trip I played with Neutral as well as holding the speed down on steep slopes and regenning like crazy. The problem with Neutral and the Tesla is that its Cd is so low that the thing just keeps going faster and faster...

Without a controlled test on the same stretch of road on which one has the ability to go both at 70 mph and 35 mph to do comparative measurements, we're still at an impasse. An early Sunday morning on the Interstate near me might work at 35mph for a few minutes...
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

JoeS
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Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: Regen vs Neutral and speed for max range

Wed Aug 15, 2018 11:50 am

Forum readers will recall that Aerowhatt and I have been embroiled in a discussion as to whether regeneration and slower downhill descents will increase an i-MiEV's range as compared to putting the i-MiEV into Neutral and simply coasting down the hill. Aerowhatt is a proponent of coasting and, from a practical standpoint, I also do that all the time; however, the theoretical challenge on the table is still there.

The discussion boils down to whether there is a higher or lower amount of stored energy which results from a lowered aerodynamic drag (from going slower) and regen power plus the power consumed by the engaged motor/inverter combination when compared to simply coasting whereby the car is still consuming a steady (1.3A?) irrespective of speed. [That's an awkward sentence that needs to be rewritten]

The metric to prove/disprove this was the change in State of Charge between the top of the hill and the bottom of the hill. Unfortunately, the resolution of this reading (via CaniOn) is only 0.5%, which is inadequate for short-stretch controlled testing. In my case, I don't have a long-enough downhill where the car will coast at a fixed speed in Neutral.

Never one to give up I've gone back to looking at a short stretch (0.4 mile?) of freeway with a nice steady downhill where the i-MiEV holds a constant 65mph in Neutral. I'm willing to go back on a Sunday morning with negligible traffic and kick the i-MiEV into regen and thus go down this hill slowly in an attempt to prove (or disprove) the hypothesis.

Let's ignore SoC, and try CaniOn's energy consumption over distance readout.

I haven't tried it, but if we reset CaniOn at the top of the hill and then take the Wh/km (or non-metric equivalent) reading at the bottom of the hill, using both driving techniques, will that prove anything? Let's discuss it before I try it.

Aerowhatt, you had published some compelling numbers in another thread which showed that engaging the motor/inverter was terrible compared to coasting in Neutral, but I couldn't readily find them. Perhaps summarize your findings on this thread?

Incidentally, the location of my "test" hill is (using Google Maps) 37.3860966,-122.2056714, but I have to re-learn to use GPS Visualizer and come up with an exact Start and Stop point on this road for the test.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
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Location: Biloxi MS

Re: Regen vs Neutral and speed for max range

Thu Aug 16, 2018 9:04 am

All in all, I think neutral is hard to beat if you have a straight downhill stretch where the car will coast at about the speed you want without the need for either slowing or accelerating on portions of it - Anytime you introduce electronics into the equation, there are losses, caused by getting DC from the power source, converting it to AC to power the motor, or regenning AC and converting it back to DC to recharge the batteries. If you were on an Eco Challenge mileage run, you would be using the coast mode as much as possible and you would be going further on less juice, no question

It's a shame Mitsu didn't give us an easy way to make use of the coast mode - A paddle on the steering wheel where you don't need to fiddle with the darned shifter every few seconds would have been really nice. But as we all know, it was a new thing and their concentration was to make it drive as close to a conventional ICE as they could. Thinking like that left lots of good, low cost ideas left on the curb - A MAX regen paddle on the left side of the wheel and a coast paddle on the right side could have probably been done for less than $100 per car. But then . . . . some elderly driver would get confused which was which and drive through a store front and everyone would be saying "Them darned EV's are just UNSAFE!"

For everyday driving in traffic where other drivers affect how and when you can coast or slow, shifting the shifter all the time is just way too much trouble, especially when all you're really doing is making and braking switch contacts - What a ridiculous way to accomplish that . . . . and then we read about people who have shifter problems after a time, where it needs to be readjusted to get it back in sync

I've never had any range problems and the wife even less so - We got used early on to just pulling the shifter all the way back into 'B' and just leaving it there. One pedal driving. You get used to where to ease up to make the curves and corners without the need to touch the brakes. I like it even better in the Volt, as I can ease out of the throttle later and then when I need even more regen to come to a complete stop, pull the paddle on the steering wheel. No question we could be adding a few percentage points to the energy savings by constantly fiddling with things and if there was a need, maybe we could be bothered - But after 6+ years driving in B mode, it's just so simple and you don't even have to think about it . . . . it's just the simple, normal way to operate, at least for us

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

Gorfllub
Posts: 74
Joined: Sat Aug 04, 2018 6:08 pm

Re: Regen vs Neutral and speed for max range

Fri Aug 17, 2018 1:11 pm

Don,

I just made a "Coast/Neutral" button! Works great!

Going to start a new thread about it in modifications section.

JoeS
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Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: Regen vs Neutral and speed for max range

Mon Oct 08, 2018 1:05 pm

Found this very good article discussing regeneration and its limits, further strengthening Aerowhatt's position in our regen vs. neutral debate.

https://chargedevs.com/features/regenerative-braking-a-closer-look-at-the-methods-and-limits-of-regen/

Dang, gotta do some controlled tests to see if I can bolster my argument. For those of you wondering what this is all about, see this post which defines the hypothesis -

http://myimiev.com/forum/viewtopic.php?f=28&t=1685&start=20#p32826
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

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