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A button by the transmission allows you to choose between normal mode (which uses battery first, then gas), sport (which is more profligate with power when you hit the accelerator), mountain (which is theoretically more efficient at 5-percent or greater inclines), and finally hold mode (which switches instantly to gas power, saving the battery's charge for later on).
Wait how does this work? I thought mountain mode was used to generate and hold battery charge for approx 10 miles, which could be used in 'Normal' mode when required/wanted. Is mountain mode not meant to be used this way? I'm confused.
 

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It's called Mountain Mode because it keeps the battery from dropping below 2 or 3 KWHs so that you have a power reserve when you go up a mountain. A side effect is that you can charge the battery up while you are driving so that you have 8-10 miles of battery range when you leave the highway. I wish they would fix it so that it charges the battery up to 50 miles of range or so (i.e. almost fully charged but leaving room for some regen braking). I've used it when traveling so that when I leave a highway I can run on electric but 8 miles of range isn't all that helpful.
 

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Discussion Starter #5
The article is wrong: mountain mode is used before you reach a mountain, not on the mountain.
The article is not wrong as it does not detail when you activate it :)

You are supposed to use mountain mode all the time on a trip that includes mountains, and eventually a bit before if there is a risk you could reach the mountains with a depleted battery.

The whole point of mountain mode is simply to maintain a battery buffer that can be used when extra power is needed going up. So if at any point during the trip the battery would get below a certain point, the engine will kick in (or run harder if already on), to maintain that buffer.
 

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I used mountain mode on I90 yesterday from Issaquah to Snoqualmie Pass and back again. Its about 40 miles each way. It was the first time I used it. As I am new to the Volt, I wasn't sure when to turn it on. I still had 50 percent ev remaining near the city of North Bend (25 miles from the top) when I turned it on. It reserved two bars of ev. I already had passed one 4 mile long steep part near Highway 18. It went really well. Car ran fine starting at sea level on up to 3000 feet at 75 mph all the way to the top. It was still in Mountain Mode when I got to the top. Is one supposed to select back into normal mode manually when at the top of the mountain? I could try the same trip without mountain mode and see if there is a difference. I then came back down the mountain in normal mode after turning the car off (to get a cup of coffee). The coolant got up to 200 F which seems normal. I enjoyed the trip very much.
 

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No you don't have to go back to normal mode. Mountain mode is like normal mode except that it turns the engine on before the battery is empty.
 

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There are three Range Extending modes, Fully Depleted Battery, Hold, and Mountain Mode. I have yet to read any documentation suggesting any performance distinctions between these modes under any particular driving conditions. Don’t know what the reviewer means when saying mountain mode is "theoretically more efficient at 5-percent or greater inclines." More efficient than what?

Fully Depleted Battery mode is engaged when the state of charge drops to the designed "minimum soc" point of the usable soc window. Hold mode maintains the soc at the point at which Hold was engaged, letting the driver choose when to use grid battery power, allowing "at will" use of the ICE. Mountain Mode is a different kettle of fish, a pre-determined soc "hold" point (~4 bars, or 45% for the Gen 1, according to Wikipedia; ~2 bars for the Gen 2).

As Scrambler puts it, "The whole point of mountain mode is simply to maintain a battery buffer that can be used when extra power is needed going up." The maximum power output from the ICE can at times be insufficient to maintain performance under high power demands (e.g., trying to pass while driving fast uphill). When in Extended Range mode, performance can be maintained if the Volt can borrow power from an available battery buffer above the normal fully depleted soc point. The "Mountain" in Mountain Mode merely refers to the type of terrain where the use of a reserved battery buffer might be needed. MM and the MM-maintained buffer are not needed when driving down the mountain, but you should remain in MM at least until no more uphill driving is anticipated.

Nothing I’ve read would suggest that the same task (holding onto an extra bit of battery power in case high power demands require using it) cannot be accomplished by switching to Hold at the same soc level (or higher). If power is borrowed from this reserved buffer to maintain performance, both Hold and MM would then recharge the battery back to the "held" soc point.

Switching to Mountain Mode does not necessarily switch operations to Range Extending mode. 2011/2012 Volts immediately drop the estimated ev range by ~14 miles (the MM-maintained buffer size) when switched to MM with adequate charge remaining in the battery. Later models would gray out the bottom battery bars to indicate the MM buffer. The car continues to operate in Electric Mode until the soc drops to the MM-maintained soc level, and then switches to ICE-powered Range Extending mode. If the soc is already at or below that level, the ICE comes on immediately.

Not all drivers are thinking about their soc as they head into terrain where demands on performance may be heavy. MM includes a feature that automatically recharges any partially or fully depleted battery back up to the MM-maintained buffer level, so the manual suggests switching to MM ~20 minutes before you reach the uphill mountain roads. A fully depleted Gen 1 battery can be recharged while driving on moderate demand roads (i.e., before heading up the hills) within that time frame using less than a half gallon of gas, and it saves the driver the need to stop and plug into the grid for an hour or more...

The Gen 2's ICE output is far more powerful than the Gen 1's, and the MM-maintained buffer was reduced to ~2 bars. Some think it might not be needed at all, but was kept because users would expect it. At least one poster in another thread reported successfully driving a 2016 Volt through the Grapevine in California in fully depleted Normal range extending mode (i.e., no Reduced Propulsion experienced). Of course, your own Gen 2 driving might be more aggressive.
 

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If I were GM I'd rename Mountain Mode to Recharge Mode and increase the charge level to mostly full. I use it so that I have battery when I leave the highway, but 8-10 miles isn't really satisfactory for this. The Volt's ICE isn't noticeable at 70 but it is at 30. I don't know if it's because it runs more smoothly at 70 then it does at 30 or if it's nothing more than there is more road noise at 70 then there is at 30. Either way I would like to be able to travel on a highway using the ICE and then switch to battery when I get off the highway. During the first part of a trip I use Hold mode and then switch to normal when I get to my first destination, however later in the day the battery will be depleted and then I switch back to Mountain when I get back to the highway which gices me some battery when I get off the road then next time.

I would use the Mountain mode name for the L setting (M) because that seems more appropriate. L is confusing because the Volt has no transmissions and L usually means Low gear. The place where I've found L to be really useful is going down mountain roads. In an ICE car you might switch to a real L gear on a particularly steep grade but generally you just ride the brake when it's more moderate. L rides the regen brake instead of the friction brake so instead of burning your brake pads up you are generating electricity. I found that L makes traveling down hill much easier. I've used it a lot in Vermont and New Hampshire where there are very long downward stretches. For modest mountains. like those found in the East, L is all you need.
 

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The Volt's ICE isn't noticeable at 70 but it is at 30. I don't know if it's because it runs more smoothly at 70 then it does at 30 or if it's nothing more than there is more road noise at 70 then there is at 30.
Road and wind noise. The low-speed engine rumble is noticeable when it's otherwise quiet. I just keep thinking about the poor dude over there with the WRX that has to listen to his all the time.
 

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There are three Range Extending modes, Fully Depleted Battery, Hold, and Mountain Mode. I have yet to read any documentation suggesting any performance distinctions between these modes under any particular driving conditions.

The Gen 2's ICE output is far more powerful than the Gen 1's, and the MM-maintained buffer was reduced to ~2 bars. Some think it might not be needed at all, but was kept because users would expect it. At least one poster in another thread reported successfully driving a 2016 Volt through the Grapevine in California in fully depleted Normal range extending mode (i.e., no Reduced Propulsion experienced). Of course, your own Gen 2 driving might be more aggressive.
+WordPTom Thank you for explaining mountain mode. Very helpful.
 
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