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Using mountain mode to build up a charge

18848 Views 16 Replies 12 Participants Last post by  wordptom
While driving on the highway, I used mm to build up some battery charge. At this point I wanted to place the car in the hold mode to retain the charge for later use in the city. However, the hold mode was not available. Later, I realized that I had no charge left on the battery. Should I have just left the car in mm until I got in the city?
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The introduction of Hold mode in the 2013 Volt complicated the power accounting system.

As the manual says, Electric Mode driving uses grid power stored in the battery and any regen that occurs while in Electric Mode. The energy usage screen records this as Electric Miles and kWh Used (= grid power used less regen put back into the battery). Everything else is Extended Range Mode, displayed as Gas Miles and Gas Used, including miles driven when the ICE is running, and miles driven on battery power put there from regen that occurs while in Extended Range Mode and battery power put there by Mountain Mode recharging.

Hold mode preserves grid power for later use. If you switch to MM when the battery state of charge is below the MM-maintained level (~4 bars for a Gen 1 Volt, ~2 bars for Gen 2) but above the fully depleted level, MM will recharge the battery to the MM-maintained level. During the process, MM-recharged power increases the battery’s soc above the level of the remaining grid power. If you then switch back to Normal, neither Hold nor Electric mode should be available until the battery soc drops back down to the existing grid power level. Yes, you will drive on battery power, but it should register as Gas Miles because the power was put there by running the generator. Once the MM-recharged power has been used and the soc is back to the grid power only level, Hold or Electric Mode should become available.

Note: 2011/2012 Volts had a glitch that under the above circumstances, switching to Normal would immediately switch the car back to showing the battery icon and recording the miles as Electric Miles. Using this MM-recharged power, however, would not add to the kWh Used number.

If you instead switch to MM after the battery is fully depleted, you won’t have any grid power to "save for later use" until you plug into the grid and recharge. If you switch back to Normal after MM recharges the battery from fully depleted, the soc is, indeed, above the minimum level, but there is no grid power there, and Hold should not be available, and the ICE should continue to operate as if the battery were fully depleted (even though the MM-maintained buffer now exists), and miles should be recorded as Gas Miles.

However, if you stop and turn the Volt off and back on again after using MM to recharge, the accounting gets confused. The computer is now told that the battery’s soc is above the minimum level, and so the car proceeds on battery power and records the distances as Electric Miles. The kWh Used number, however, should not increase while MM-recharged power is being used (it’s not grid power). I drive a 2012 Volt with no Hold mode, so I cannot test to see if turning the car off and on again will enable the use of Hold mode to "save MM-recharged power" for later use.
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" you will drive on battery power, but it should register as Gas Miles because the power was put there by running the generator."
If this this is the reason why it is not visible on power flow that during MM the battery is charging?
Not sure what your question is. Using Mountain Mode does not necessarily involve any recharging of the battery.

Switching to Mountain Mode, for the most part, is like telling the Gen 1 Volt to "switch to this special version of Hold Mode when the battery state of charge is at 45% of the full battery capacity" (according to Wikipedia).

If you switch your Gen 1 Volt when your battery still has lots of green bars of range, the car stays in Electric Mode until the SOC drops that low (that’s around ~4 bars, or ~14 ev miles of range remaining), and then, in effect, "switches to Hold Mode." No battery recharging.

If you switch just as you’ve used up the sixth green bar, the car might, in effect, switch then into the MM version of Hold Mode. No battery recharging.

It’s only if you don’t switch to MM before the state of charge drops below that point (or the battery is fully depleted) that when you do switch to MM, the system will recharge the battery to the MM-maintained SOC point.
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