Cruise Control

[pasowino]

Hmm, i was driving down the Cuesta Grade near San Luis Obispo (about a 1,200 foot drop) and the car in ECO mode and cruise control set at 60 MPH it held me perfectly at 60 MPH all the way down.

One thing that comes into play here is probably the SOC of the battery. If your running at greater than 80% charge, there is limit on how much regen the system is allowed to deliver to the battery, so the only other option is to use friction breaks. I wouldn't expect a car to use the breaks automatically, but it seems that it should at least max out the regen load on the generator to try to slow you down.

 

[GerryAZ]

aqn, are you 80% charged? ECO mode? What speed? Seems like less regen braking at lower speeds.
I have yet to see more than a few mph gain going downhill with ECO mode.

Finally had a chance to confirm it yesterday.

I set the cruise control at 35 mph (the speed limit in my housing development) and the car proceeds for about 3-4 seconds at that speed before I reach the steep downhill. I am in ECO, which I'm in 99% of the time. 1214 feet later, with the re-gen max'ed at 5 dots/30 kWh, I'm doing 52 and gaining speed rapidly. I hit the brakes at that point.

Info from Google Earth:
Start (on Jester Blvd at Winterberry): 30'22'30.45"N 97'47'54.85"W 943 ft elevation
End (just before the big right hander): 30'22'20.51"N 97'47'55.79"W 795 ft elevation
148 feet drop over 0.23 miles (1214 feet) = 12% grade

It looks like cruise control was doing all it could to control speed since it was using maximum regeneration--12% is a steep grade. The only way cruise control could do any better on that steep grade would be to automatically apply friction brakes. I personally like the cruise control to accurately maintain the speed so would not be opposed to a software change which would accommodate that. I would not want to see software updates which allow speed variations of +/- 5 MPH as some others are advocating.

Gerry

 

[aqn]

Hmm, i was driving down the Cuesta Grade near San Luis Obispo (about a 1,200 foot drop) and the car in ECO mode and cruise control set at 60 MPH it held me perfectly at 60 MPH all the way down.

1200 foot drop over how long a distance? What was the grade?

One thing that comes into play here is probably the SOC of the battery. If your running at greater than 80% charge, there is limit on how much regen the system is allowed to deliver to the battery, so the only other option is to use friction breaks. I wouldn't expect a car to use the breaks automatically, but it seems that it should at least max out the regen load on the generator to try to slow you down.

The re-gen was max'ed at 5 dots/30 kWh. The LEAF did not use the service brakes to maintain speed. Or, to be precise, with the re-gen max'ed, my LEAF gained speed going down that hill, 35 mph - 52 mph.

I should also note that there are a couple of other seemingly long and steep hills here that turned out to be 10% grade and my LEAF does not gain any speed going down those hills. (The hill I saw the speed increase on is a 12% grade.)

For example:

30'17'56.49"N 97'49'38.95"W to 30'18'16.97"N 97'49'31.24"W
is a drop of 193 feet over 1906 feet: 10.1% grade

 

[aqn]

Hmm, i was driving down the Cuesta Grade near San Luis Obispo (about a 1,200 foot drop) [...]

1200 foot drop over how long a distance? What was the grade?

I looked it up. If you're referring to the stretch of 101 South bound into San Luis Obispo, it does indeed drop 1200 feet, but it's over about five miles. That's a 4.6% grade.

 

[lanceaz]

Most Chrysler cars will hold the speed down to the set speed while descending hills by shifting down as needed. They have been doing this for many years. I rented one in August of '98 that did this and was surprised that it did it, so much so that I still remember it.