[Xzlon]

My goal is to arrive at home in CS mode to extract all the charge from the battery and minimize gas usage. Since the last 23 miles to my home is a 2250 ft elevation climb I can do that on most trips out.

 

[ammPilot]

I used MM as a sort of Hold Mode surrogate, as discussed here, on a recent long unrecharged trip. For the low-speed driving in the middle of the trip (an out-and-back) was in Normal Mode, drawing on the reserved battery charge maintained in MM. Once back on the freeway, I switched back to MM until just within EV range of home (based on a quick switch from MM to NM to check the NM battery range).

Worked great.

What I don't know is whether this actually does save gasoline. It seems logical that (and according to the laws of thermodynamics), even with good use of regenerative braking, stopping and then accelerating back to speed (even if that's 30 mph) is less efficient than just maintaining that steady 30 mph. Tony, my GM Volt Advisor, called to introduce himself this evening; I posed this question to him, and he said he'd bring it up with the Volt engineering team.

 

[George S. Bower]

Mountain Mode would be perfect in the following situation. Let's say you have a 60 mile round trip to work and you can't charge at work. The first part of the trip is a steep climb. Without mountain mode you will use up all your battery climbing the hill. Then CS mode for the drive home. You are then using the ICE at a low load condition where it's SFC is not the best. Using the ICE at the front part of trip going uphill at a high load is better., so you use mountain mode up the hill then switch out of MM. You would have to figure out exactly how long to go in MM before switching out. the object would be to get home w/ 1 mile of EV range left and the ICE does not come on.

 

[MichaelH]

Your scenario would work if the Volt had the "Hold Mode," which it does not. In Mountain Mode, what would happen is the Volt would operate in EV until is depleted to the set point (~40% SOC, ~13 miles range left, but it would say 0 miles). Then the ICE would come on until you changed back to Normal Mode, at which time it would say somethinglike 13 miles range left.

 

[Xzlon]

Has anybody tried Mountain Mode (MM) while State of Charge (SOC) of battery is high (over 45%) in EV mode?

It is known that if you shift to MM in Charge Sustain (CS) mode engine would top the battery up to 45% SOC as well as providing enough power for current driving power demand.]



STUDY OF FORCED MOUNTAIN MODE VS NORMAL MODE

I have a route I take often that is right at 100 miles, with several steep uphill and downhill grades. The results of hypermiling and select use of MM is suprising and shows that GM has done about as good a job as possible to achieve best efficiencies.

Trip 1: 100.1 miles 58.1 CD miles 42 CS miles 1.59 gallons 12.92 KWHR Cost(gas + Elec) $10.594

Trip 2 : 98 Miles 43 CD miles 55 CS miles 1.55 gallons 13.22 KWHR $10.50

Trip 3: 99.4 miles 61 CD miles 38.4 CS miles 1.59 gallons 12.89 KWHR $10.575

The difference in trip lengths is the selection of the restaurant

So I conclude that at the current price of gas and electricity here any trade off between runing entirely in Normal vs trying to use MM to improve effeciency is at best a push. So I guess I will run in Normal for these trips.

 

[sgc]

I spoke with a GM employee who said that when they take Volts to publicly show the car and want to be able to have enough charge for the public to experience the battery only operation, they drive in MM to the event to preserve charge. He said it will save about 5 miles of charge to allow the public to experience the car in CD. So yes, it works, but not so as to completely preserve or hold the charge.

 

[Rusty]

He said it will save about 5 miles of charge to allow the public to experience the car in CD.

Which tells you how hard people thrash the Volt during demos

I don't generally drive mine gently (though getting to be more gentle than my last gasser) and I usually have 11 miles from a full MM SOC. But the car learns over time what to expect.

 

[sgc]

My challenge has been to learn to drive with electricity efficiency in mind. When I'm alone I play that game. When I'm with others and we need to go somewhere by a certain time, then I can't. Hard to adjust to "gentle & efficient" driving habits.

 

[ammPilot]

Hauling out this thread, dormant for a while.

When in CS mode last night, in some rolling hills on the San Francisco Peninsula (I-280, for you fellow Bay Area folks), it seemed to me that the ICE's speed did not directly correlate with the car's speed. There were times when I was accelerating and the ICE sounded as though it was not going any faster, but without a direct tach readout, I could not be certain. At the end of the trip, when in CS and Normal Mode, I think the ICE shut down at a traffic light: no wasted gasoline idling at the light.

WOT, Scott, Rusty, etc.: can you confirm this? (It makes sense to me: the battery is a big buffer, and the ICE is running just to maintain SOC. If the SOC is in good shape, you won't need to draw hard on the ICE until the SOC drops a tad.)

How does this relate to MM? We've discussed using MM to maintain SOC, with a goal of reverting to Normal Mode for in-town driving in the middle of the trip (but beyond CD-only range). Is this, in fact, net more efficient? In a conventional ICE-powered car, in-town stop-and-go driving with idling in traffic or at traffic lights is very hard on fuel economy. Is this the case with the Voltec powertrain?

 

[Slapshot28]

I have been using MM a bit more lately on longer outings, primarilly because I wanted to be in stealth mode during certain portions (like when driving up the driveway to my son's girlfriend's house... okay, ego matters).

A couple thoughts now have occured to me:

1) MM must be very powerful at battery charging. It takes minutes, not hours, to raise the battery SOC (amazing).

2) As long as I arrive home at the end of the outing with the battery fully depleted, I've succeeded (no wasted gas).

3) MM efficiency may be relatively high (no extra heat loss), so it's a zero-sum game (MM is okay for managing SOC).

I'd be happy to hear confirmations or contradictions.

Chris

 

[Xzlon]

I have been using MM a bit more lately on longer outings, primarilly because I wanted to be in stealth mode during certain portions (like when driving up the driveway to my son's girlfriend's house... okay, ego matters).

A couple thoughts now have occured to me:

1) MM must be very powerful at battery charging. It takes minutes, not hours, to raise the battery SOC (amazing).

2) As long as I arrive home at the end of the outing with the battery fully depleted, I've succeeded (no wasted gas).

3) MM efficiency may be relatively high (no extra heat loss), so it's a zero-sum game (MM is okay for managing SOC).

I'd be happy to hear confirmations or contradictions.

Chris

The most cost efficient use of MM I have experienced is to use MM (during a SOC condition that will allow MM to force the ICE to run) when travelling uphill grades and Normal for all flat and downhill travelling. That seems to utilize the ICE to add the extra charge to the battery while at the same time assisting in driving the car. Not a big difference in cost per mile but the best I have achieved. On one 98 mile trip I got 64.2 mile CD and 33.8 CS miles(1.29 gallons of gas). Using MM on flat land driving adds to cost per mile.

 

[gwmort]

I am mildly fascinated by mountain mode.

Today I had a long highway drive where I knew I'd be using gas anyway, so I did some playing around with MM.

When I only had 3 miles AER left I put it in MM for about 6 minutes, I burned about 1/4 gallon going just over 6 miles so I figure I was getting 24 mpg in that mode, I switched back to Normal, and now had 9 miles AER left, so in reality I got 6 "free" miles on top of the 24 mpg I was burning or 12 miles traveled for 1/4 gallon of gas for 48 mpg.

I'm wondering if there is some sort of hyper-miling pulse and glide equivalent that would cycle periods of MM with periods of EV?

 

[scottf200]

<snip> so in reality I got 6 "free" miles on top of the 24 mpg

Not exactly. When running in MM with 3 miles left the ICE was running very hard to recharge your SOC to about 13 miles. ie. lot harder than it needed to just to propel the car...thus used more gas than needed to.

For most such a technique would be most annoying. loud rpm, quiet, loud rpm, quiet. Certainly that could/should not be worked into any EREVs design by GM or others. Imagine the field day the writers would have on that.

 

[marlow]

a good little test, which seems to show that battery recharging in mountian mode is fairly efficent, however the numbers are small and rounded, which could introduce siginificent error.
how fast were you trvaling at during that 6 minutes?

 

[gwmort]

a good little test, which seems to show that battery recharging in mountian mode is fairly efficent, however the numbers are small and rounded, which could introduce siginificent error.
how fast were you trvaling at during that 6 minutes?

Cruising at 68 (on cruise control)

 

[marlow]

I drove from Michigan to North Carolinia and back via I 77, through the mountians.

I drove down in mountian mode and had no problems, I drove back in standard mode, between 70 & 75 MPH and about 1/2 way throught the mountians I got the "reduced propulsion" message for a few minutes and my speed droped to about 68 MPH.

It makes me think that mountian mode would be superior to the hold mode, if we could adjust the battery reserve level (or fixed hold level) in mountian mode, that would combine the best of both modes.