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My First "Propulsion Power is Reduced" Experience

14554 Views 15 Replies 9 Participants Last post by  DMC5180
Living in Phoenix, I have had no need to use Mountain Mode until today when I had to drive to Show Low. I hadn't realized just how critical it is to use Mountain Mode when driving in the mountains. I assumed the engine generator would take care of my needs on this trip. I was wrong.

Driving across the Valley, I used up all the traction battery power, and as I started up the mountain with the engine running things were fine for a bit, then the "Propulsion Power is Reduced" message came up and the car slowed, then slowed some more, then I had to pull over and stop. Having read related posts on this forum I knew what was happening, so didn't panic. Put it in Mountain Mode, waited just a couple of minutes for some battery charge, then all was well. Carried on the trip with no further concerns.

Once again, the Chevy engineers knew what they were doing in the design of the car to include Mountain Mode. Once again, however, it goes to show that driving a Volt requires some understanding of how it works.

I understand the Gen II cars have more power available from the engine generator such that Mountain Mode isn't really necessary. Yet another reason to lust after a Gen II Volt.
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Found another part of the manual with more info on the modes.

Tried Mountain Mode today on a long steep grade. I had been on hold mode saving my battery and I went to MM and it just went up the hill on the battery, never started the ICE.

It doesn't have any problem on battery, I like to use hold but it feels under powered sometimes.
Sounds like you didn’t actually manage to use up enough battery to drop down to Mountain Mode. If you switched your 2013 Volt from Hold into MM with more than ~4 bars of power remaining, you were driving up that hill in Electric Mode.

When you switch a Gen 1 Volt into MM with more than ~4 bars of power still in the battery (~2 bars for Gen 2), you continue driving in Electric Mode on battery power until the battery’s charge has dropped to that ~4 bar level. At that point, the ICE starts, and it’s just like you’re driving in Hold Mode.

You can test this out any time... when you switch a 2011/2012 Volt into MM, the ev range immediately drops by ~14 ev miles (the MM buffer). Later mode Volts "gray out" the bottom battery bars. If you then still have green bars remaining, you continue driving on grid battery power (2011/2012 owners continue until the new range estimate drops to 0). Switching back to Normal will make that reserved power available again.

If you switch after you drop below that 4-bar (or 2-bar) level, or wait until the battery is fully depleted, MM includes a "feature" that recharges the battery to the 4-bar (2-bar) level as you drive, burning a little more gas for this purpose. This allows you to recharge that buffer without having to stop and plug in to the grid before heading into the mountains. (If you later switch back to Normal, you drive Gas Miles on this battery-power-created-by-burning-gas until it’s used, then the car switches back to green bars of grid power.)

The Self Charging Chevy Volt youtube video shows a 2012 Volt with a fully depleted battery being recharged via MM. The procedure takes 15 minutes, and uses 0.36 gallons of gas. The video shows this happening while the Volt is parked, but I’ve seen no reports that suggest the process takes any longer or uses any more gas if done while driving along in moderate conditions. That’s why the manual tells you to switch to MM about 15-20 minutes before heading into the mountains.
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So normal is the best mountain mode if you have the juice?
No, Normal is not the best mountain mode if you have lots of juice, for this reason:

Lots of hilly terrain can be handled just fine by the Gen 1 in Extended Range Mode with a fully depleted battery, but some conditions call for being prudent and making sure you hang on to that MM-maintained buffer. When heading into such mountains in a Gen 1 Volt, it’s wise, even with a fully charged battery, to switch into Mountain Mode and remain there until you’ve passed the summit and any other uphill driving area where high power demands may drain the battery. You wouldn’t want to just stay in Normal, successfully pass over the next-to-last summit using the last of your battery charge, then go into Reduced Propulsion Mode when cresting the final summit.

Mountain Mode has been poorly named. It’s not a special mode that provides the Volt with special performance characteristics for driving in hilly terrain that would be unnecessary on flat ground. Perhaps it should be called Hold Mode at Fixed Battery Charge Level.

The 2011/2012 Volts had no Hold Mode. Once it was introduced in the 2013 Volts, setting Hold at the MM-maintained level or higher was an adequate substitution when driving uphill on mountain roads. Choosing MM over Hold seems to offer no particular advantages, except as a means of recharging a depleted battery to provide the buffer needed for the high-demand conditions. Some drivers just switch to MM as soon as they depart, knowing the Volt will then transition from Electric to Extended Range Mode when the battery soc drops to the MM-maintained level.
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I actually tried the Self charging Via MM yesterday... I drove in N(L) until I was down to 3 mi. and 1 bar showing. It was about 2-3 miles before the 5% Uphill grade. I switched to MM with 58 miles range showing in the fuel tank... By the time I reached the Up hill grade it gained back 1 bar. I ended up getting stuck behind a truck with camper trailer in a 1 lane construction zone climbing the hill at 45 mph. When I crested the hill the gas range was already down to 50 ( lost 8 miles in 4 miles). I drove another 10-12 miles in MM The Low fuel message came on in the middle. My gas range had dropped to 36 when the message came on. About 5 miles from home and a couple miles out of town, I switched Back to Normal mode since the battery was filled up the Red line in MM. GOM showed 18 EV miles. A couple Miles later , I stopped for Gas, then Proceeded Home. when I pulled in the Drive way I was Down 16 EV mi.
A couple of things you may or may not have noticed in all the excitement of your first MM use:

You switched into MM with ~1 bar of grid power remaining. The 58-mile gas range estimate that then appeared would have suggested you had less than 2 gallons remaining (window sticker rating for the Gen 1 is ~37 mpg). It takes 0.36 gallons of gas for MM to recharge a fully depleted 2012 Volt battery, so your engine/generator likely used less than that over the next ~15 minutes to recharge to the MM-maintained level (you were going slow in the construction zone). After that, the remaining gas was being burned at your car’s normal gas mileage rate in Extended Range Mode...

When you switched back to Normal as you neared home, the ICE should have stopped and you then drove on battery power. Normally, the first bit of distance on that MM-recharged power should have been recorded as Gas Miles (MM-recharged battery power is gas-created power, not grid power) until the battery state of charge dropped back to the ~1 bar level where it was when you first switched to MM. When you stopped for gas, however, and turned the car off and back on again, it messed up the accounting. The computer now recognized the battery SOC was above the programmed minimum, and might have started counting the miles as Electric Miles (without changing the kWh Used number!). The computer remembers where that grid power SOC level is, though, and once the battery SOC drops down to that point, you’re once again driving on grid battery power and the kWh Used number will increase. Of course, fully recharging will reset all that.
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