In my 55 years of driving I've run out of gas at least half a dozen times, and my memory doesn't seem to be getting sharper in my seventies. So, let's say I've had my dream car for a year, now, and pretty much forgotten about ever having to put gas in.

One day I take off for my favorite place in the world – Yosemite. The battery is full, and I've topped off the gas tank. I take the Big Oak Flat Road, Highway 108 and 120. Going up Priest Grade at full speed is exhilarating,:D if a bit costly. (It's a 1400 ft. climb in 5 miles on the new road, only 2 miles on the old road, but that is very slow.) I arrive safely at Crane Flat, 6159 feet elevation and 185 miles from home, then plunge down the 17 mile hill to Yosemite Valley at 4000 feet, regen pumping mightily. After spending some time in the Valley, I drive up to Glacier Point, at 7200 feet, and back to the valley, a 60 mile round trip. I've almost made it back up to Crane Flat when ... OOPS!:eek: The gas tank is dry.

There is a gas station at Crane Flat, if I could only get there. Is there some way I could draw on that 30% reserve in the battery on an emergency basis?:confused:

I might be able to get the car turned around somehow, though it would be tricky on the narrow, twisty, mountain road, and coast back down to Yosemite Valley, but there is no gas station there, even if I could.

Highway 140 follows down the Merced river from Yosemite Valley, and I am almost positive I could negotiate its occasional slight rises on regen juice, but the first gas station in that direction is in Mariposa, 45 miles from where I am. And the hooker is that the highway, after dropping to 1500 feet along the river, climbs 1500 feet over a pass before it drops into Mariposa.

Is there any hope for me in either direction? Or am I doomed to a very expensive tow truck call?:confused:

I believe the engine will shut off when you're back up above a certain level so in all of that regen, you might have brought the battery reserve up enough that the engine wasn't running the whole time. I don't think you can access that 30% in an emergency, although I don't think anyone on this forum (or outside GM for that matter) knows if the 30% reserve will be available when the gas runs out for an emergency limp home. They kind of toyed with that idea over a year ago in the development, but I don't think it will be implemented because too many people would just not put gas in it and it run their 50 mile commutes and make it an every day thing which would shorten the longevity of the battery that's warrantied by GM.

I can see it now:

"WARNING! Your fuel supply is exhausted and your battery charge status is at the 30% cut-off point. You may choose among the following options:

-> Do nothing

-> Use On-Star to call the nearest service station for a fuel delivery

-> Use On-Star to call the nearest service station for a recharge

-> Authorize the emergency use of the battery below the 30% cut-off threshold (WARNING! This will void your battery warranty!)"

Hey, it could happen . . .

There were several questions implied by my fantasy.

#1. If you add up the miles I listed and allowed for 15 miles of roaming in Yosemite Valley, I hypothetically ran out of gas at about 290 miles. Is that likely to be high or low for that kind of mountain driving? I would have been tempted to say 'high' except that I drove that route in my Prius a few years ago. I noticed to my surprise when I got up to Crane Flat the first time that my tank average was 49 MPG. I also felt comfortable not buying any gas until I got back to Oakdale, completely out of the mountains.

#2. The question that omnimoeish and Altazi picked up on was the emergency battery power. I tend to agree that it is likely it would either not be permitted or would void the battery warranty.

#3. If I was on a gigantic roller coaster that dropped from 6000 feet to 1500 feet and back up to 3000 feet, I would have no fears as to whether it would make it over the hump. [Whether my heart could stand the ride would be quite another matter] So the question is, how good is the regen anyway at recovering energy? A net drop of 3000 feet in 45 miles is an average downgrade of 1¼%, if I've figured correctly. I think the car should be able to coast down a 1¼% grade, though I guess that would be another part of the question.

If you plan "risky" trip, use a long ranger like this one, this shoul allow you to go as far as any of those gas stations : http://yosemiteblog.com/where-to-get-gas-in-yosemite/

Best regards,

JC

http://www.evnut.com/images/rav4/rav_longranger/rav_longranger02.jpg

I can see it now:

"WARNING! Your fuel supply is exhausted and your battery charge status is at the 30% cut-off point. You may choose among the following options:

-> Do nothing

-> Use On-Star to call the nearest service station for a fuel delivery

-> Use On-Star to call the nearest service station for a recharge

-> Authorize the emergency use of the battery below the 30% cut-off threshold (WARNING! This will void your battery warranty!)"

Hey, it could happen . . .

What Altazi is suggesting could be accomplished in practice. Gm could just add an algorithm that adjusts the battery warranty appropriately. Tesla allows the user to select different pack settings. In one mode the user can select a battery range of 100% to 30% (approx=my recollection). So for the volt, with judicious use, a user could get almost 60 miles AER.

I don't know what the regen rate will be like. Remember, you can always bring a gas can with you in the Volt, just throw it in the cargo area in the back. That's probably not a scenario that the average person will face where they are really stretching to make it to a gas station.

We don't know what the fuel capacity is, and we don't know what the mpg in extended range mode is going to be, we also don't know exactly what the regen is like (it might be pretty good as you are going down those steep hills, or maybe it won't make much of a difference).

OK, so in theory, a battery at 30% = 12 miles of range assuming it could push every last electron out of the pack. Probably couldn't, but lets assume it could.

that's = less then 1/2 a gallon of gas in range.

See where I'm going with this?