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FOCUS Chevy Volt I The Chevy Volt...And Its Role In Policing MOUNTAIN AND HOLD MODES y switching to Mountain mode, the driver manually activates the gas engine. The gas engine then provides electricity to the drive motors, and also provides electricity to charge the main battery. The original purpose for Mountain mode was to charge the main battery enough to drive 60 mph up a 5 percent grade without loss of speed. You will need the half charged battery that B p The Volt can be operated in four driver-selected modes: Normal (battery-only), Sport, Mountain and Hold. In Mountain mode, you can recharge the depleted battery to about half charge in about 10 miles. In Hold mode, you can hold whatever charge the battery is at, including fully charged. (Photo courtesy General Motors) comes from Mountain mode and remain in Mountain mode. Of course, Mountain mode is something you use ahead of time, i.e., charge the depleted battery before the need! However, you can use Mountain mode anytime you want to charge the battery to half level. That will produce 15 to 18 miles of battery-only driving once you switch it to Normal mode. So, why mess around with plugging in the Volt to charge the battery? Why not run it in Mountain mode all the time? Two reasons. First, the Mounting mode produces electricity in the most expensive and least effcient way. Second, the Mountain mode only charges the battery half way, or maintains the battery at about half-charge (45 percent State of Charge). To fully charge the battery, you have to plug it in. To reduce the rate of capacity degradation, the fully charged battery is limited to an 85 percent SOC. The fully depleted battery is limited to a 30 percent SOC. Instead of using Mountain mode to charge the battery for specifc times when battery propulsion is the most effcient, use 24 Police Fleet Manager Jan-Feb 2013 24 Police Fleet Manager Jul-Aug 2012 the Hold mode. Driving with the gas engine to power the propulsion motor in Hold uses less gas than driving in Mountain mode. In Mountain mode, the gas engine has to power both the propulsion motor and the generator to recharge the battery. One way to use the battery for city driving involves Mountain mode. Change from Normal mode to Mountain mode when the remaining battery capacity is equal to the amount of city miles coming up. When you change from highway driving to city driving, change back to Normal mode for batteryonly operation. Remember now, the Volt uses more gas in Mountain mode than in battery-depleted Normal mode, so max overall effciency is a balancing act for the green enthusiast. In Mountain mode, the system is working to a high-voltage battery state of charge. The resultant generator rpm might be higher. The generator speed is a function of many factors including the high-voltage battery starting point, vehicle pedal request, current ambient conditions, and road grade.��It is not simply an increase in gas engine rpm compared to Normal mode. p q The Volt has two electric motors (primary traction motor, secondary generator-motor), three clutch packs and a planetary ring gear and planetary gear set (sun gear, planetary ring gear and planetary carrier. Power transfer is absolutely seamless and transparent. (Photos courtesy General Motors) Hold Mode The most signifcant change for the 2013 model year is the addition of the Hold mode. The Hold mode allows drivers to decide exactly when they will use the battery-only, i.e., when to use the Volt in the most fuel-energy effcient way. When the battery is depleted, the Volt gets better gas mileage on the highway (40 mpg) than in the city (35 mpg). So it makes sense to do as much fully electric driving as possible in the city, and as little fully electric driving as possible on the highway. The Hold mode is a big deal for drivers who mix highway and city driving. The electric motors are most effcient in suburban, urban and heavily urbanized driving. Not so much in highway and rural driving. With a mix of city and highway driving, Hold allows the driver to isolate the main battery. In Hold mode, the gas engine powers the generator motor to drive the Volt. The battery is not used at all. Here is how Hold pays off. The Volt is fully charged overnight. Start the inbound commute from the suburbs with a drive into the city. Put the Volt in Hold mode as you drive at higher speeds the frst few miles. Change back to Normal mode (battery-only) for the slower, stop-and-go driving. Start the out- bound commute in the default, Normal mode (battery-only). Using only the battery in slower traffc, get as far as the battery will last under the conditions that battery-only is the most energy effcient. Depending on a number of conditions, the gasoline-produced electricity may only be needed for a few minutes during the entire travel. When the gas-engine is activated, it will be under driving conditions that are better suited to gas-generated electricity, where battery-only operation is less energy effcient.