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I've read about a few instances of owners forgetting to engage Mountain Mode before a hilly climb, and receiving the "propulsion power reduced" alert. Does this mean that Volt can't climb steep grades on the gas generator alone? Is there a specific grade threshold to consider for Mountain Mode (i.e., above X% grade, MM is recommended)? Obviously, Volt doesn't need Mountain Mode for gentler climbs.

I'm out in California and often head out to Tioga and other high mountain passes, so any input is appreciated. Thanks.
 

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It can, just consider that it is a 4000 lb 84 hp car on engine only. All mountain mode does is hold 40% charge or so to use as a buffer for extended runs where you need more than 84 hp. The electric motor is something like 150 hp (less at highway speeds). You need that to maintain speed on mountain passes.

Also remember that at elevation air breathing engines lose power due to lower air density. 3% per 1000 feet. At 10k feet an ICE might lose 30% of its HP. Electric doesn't care about elevation nor air density . The Volt's poor ICE would have only 58 hp at 10k feet elevation. A steep grade might mean 40 mph on the engine alone.

Several edits above.
 

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I've read about a few instances of owners forgetting to engage Mountain Mode before a hilly climb, and receiving the "propulsion power reduced" alert. Does this mean that Volt can't climb steep grades on the gas generator alone? Is there a specific grade threshold to consider for Mountain Mode (i.e., above X% grade, MM is recommended)? Obviously, Volt doesn't need Mountain Mode for gentler climbs.

I'm out in California and often head out to Tioga and other high mountain passes, so any input is appreciated. Thanks.
There is no hill that the Volt can't climb on generator power alone (except for insanely steep ones it can't climb at all - with a ~4000 pound weight and ~2000 lbs of tractive force, the car is presumably unable to start on or accelerate up a 30 degree slope.)

However, steep hills will require slowing down if the battery is drained.

In general, if you think it might be an issue, just put the car in Mountain mode and leave it - as long as you get a chance to use the electricity before your next charge, it does no harm to leave the car in mountain mode for the whole trip.
 

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The question isn't "can it climb?" but "How fast can it climb?"
If you want to do it at 70+ MPH, you'll probably need MM. If you go slower, it won't matter.

The engine can provide at most 55kW. So if you keep the power output to 55kW or less on the dash, you can go at that speed "forever"
 

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It can, just consider that it is a 4000 lb 84 hp car on engine only. All mountain mode does is hold 40% charge or so to use as a buffer for extended runs where you need more than 84 hp. The electric motor is something like 150 hp (less at highway speeds). You need that to maintain speed on mountain passes.
Actually 74hp, this being the limiting power of the generator in serial mode. I don't believe it will enter dual motor/engine lock up mode while under high torque loading, at least that's my understanding, so you'd be climbing steep grades as a 4,000lb 74hp serial hybrid.

55kW can raise a 1800kg mass at 3m/s, which is equivalent to rising up a 15% grade at 45mph (before even looking at other on-road drag losses). You have double that power (thus double the vertical rise) with the battery driving the main traction motor, not counting the other drag losses (which obviously become significant if you get up to 70mph).

Does that cover the question?
 

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I go through Vermont mountains near the ski resorts all the time and never have to use mountain mode.

In most scenarios you don't need it, but on a small percentage of steep grades and 65mph driving, engaging it in advance can help.

I have personally never needed it, driving through mountain passes in NH and VT all the time without an issue... Including roads that are steep enough to have runaway truck ramps.
 

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I can't provide a technical response but have some good real life experience. I live in Denver and use my Volt to go skiing frequently where I have lots of up and down driving. I've tried using all my battery power and MM for the hills. The only hill where I've needed extra power is a steep 7 mile grade from Silverthorne to the Eisenhower/Johnson tunnel and if I've drained the battery, I get the power reduced/low propulsion message and am lucky to hold 50 mph. With MM, I can cruise at 70+ the whole climb.
 

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I prefer to use Hold mode to keep about a half charge in the battery...functionally the same as MM, but I'd rather keep cheap electricity in the battery that's sourced from home, versus depleting the battery then using gas to charge it back up using MM.
 
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