In a Chevrolet Volt webchat on Dec. 9, the energy integration engineer for General Motors Corp., Larry Laws, gave some insights on how to get the most from your electric vehicle (EV) range.
Larry Laws: Hi everyone and thanks to all of you for joining today. Looking forward to the chat. Let's get going!
Q: Below which temperature will the Volt start heating the battery?
Larry Laws: That will happen at zero degrees Celsius.
Q: My wife has a 2009 Malibu and she will drive the Volt because it's better in the snow. What makes the Volt drive better in the snow?
Larry Laws: It's actually the Volt tires that give the car good snow performance.
Q: Is there any overall energy advantage to running in Mountain Mode once the generator starts to charge the batteries so that you can run additional time later off the batteries? I noticed that the generator is really working in Mountain Mode and would assume it is using more gasoline during that time.
Larry Laws: In the energy equation, it's not better to charge the battery from the engine. It's more efficient (and better for the environment) to charge the battery off the wall. Mountain mode is used for high-load conditions.
Q: I have had my Volt for about a month. It's starting to get quite cold here in Minnesota (0 degrees this morning). I am wondering what will happen when we have a REALLY cold day, perhaps it never gets above 0 degrees, when my Volt is parked outside for maybe 8-10 hours. Will the battery be warm enough to start the car?
Larry Laws: The battery is designed to start the car at temperatures as low as -30 degrees Celsius. Below that, we recommend you keep the car plugged in.
Q: I use the OnStar warm-up function when my car is in the garage and plugged in on cold days. Because I mostly charge overnight I haven't opted for the 220v charger and use the 110 version that came with the vehicle. I've read that warming off the 110 charger will still result in the ICE coming on at times of battery depletion or extreme cold. Is that true?
Larry Laws: The 240-volt charger has more power and can preheat the cabin a little bit better, but the engine cycling is based on ambient temperature and coolant temperature and neither (240-volts or 120 volts) will prevent the engine from coming on when it is extremely cold.
Q: When one remotely starts the vehicle and it is plugged in, is it possible that the gas engine may turn on while the car heats up or does that only happen when the car is not plugged in?
Larry Laws: Yes, the engine can still turn on when the car is plugged in when it is extremely cold out to provide cabin heating. Plugging in or not plugging in doesn't change the behavior of the car in terms of the temperature in which the engine will come on.
Q: Does preheating the car off of 110 power deplete the battery at all?
Larry Laws: Yes, some energy will come from the battery, especially if it is very cold outside.
Q: Is the Volt better insulated against cabin temperature loss? When I turn the heater off in my regular car, I can feel the temp dropping immediately. I suspect pre-heating the Volt while plugged in will only feel good for a few minutes.
Larry Laws: The Volt will retain and cold the same as any other new car.
Q: Most of my driving is short distances and I haven't been using any climate controls hoping that I will conserve battery charge. Is this a good idea?
Larry Laws: Yes, not using climate control will help maximize your EV range. I say go for it as long as you're OK with the temperature in the car.
Q: After driving 5,500 miles in Volt now, I am noticing a huge drop-off in EV range starting in September. I used to be able to get up to at least 48 miles, but after September I can't break 38 no matter how hard I try. Just so you understand: I use zero heat (no heated seats, not even a fan speed at the lowest in non-A/C mode). Can the drop from 48 or more down to 38 or less be completely due to something else? Tire inflation only? Or something else? Yes, the temperature is down, but if I don't use any heat at all...
Larry Laws: That seems more than I would expect. Obviously, check your tire pressure, but that wouldn't account for that much EV range. My advice is to try turning off auto-defrost.
Q: I have been getting condensation on the inside of the windshield on a few cold days. If I don't use any other climate controls, what temp setting on the defrost should I use to conserve battery charge?
Larry Laws: The low setting would use the least amount of energy.
Q: Question about Cold an Hot during working hours. I have read a bit about maximizing the life of the battery. It appears that you will have some life loss if your car is sitting unplugged under 32F or above 90F. Is that correct?
Larry Laws: Those are the temperatures where we try to maintain the battery. The life equation is much more complicated than temperature alone, but generally, it's much colder and somewhat hotter than that.[PAGEBREAK]
Q: Drove the "demo" Volt from my dealership last weekend on a 200-mile trip (all highway), left it in "Normal" driving mode even though we did have a couple central Pennsylvania Mountains to climb. In the end we managed a 38 mpg per the on-board calculator, seems that I should have been able to do better. Was a cold day initially and the motor fired up to warm the cabin. Aside from heat settings what else could I have done?
Larry Laws: The combined EPA fuel economy is 37 mpg, so I say you did pretty well. Keep your speed to posted speeds and don't accelerate too aggressively.
Q: I noticed that my Volt consumes a lot of electricity in the first mile after a cold morning start, are there some tips to minimize the energy consumption.
Larry Laws: My advice is to keep it in the garage at night and precondition it when it is plugged in. The car will use more energy as it is warming up than when it is at its operating temperature.
Q: I've had great success with driving in Low, however I am always questioning if I should be shifting to Drive when I get on the highway. I got an exceptional 41 miles on the charge today in sub-40 temps, mostly highway driving in Low the whole time. Do you have any thoughts about using Low vs. Drive on the highway?
Larry Laws: Great EV mileage! If you're having good success with low, you should continue to have good success at all vehicle speeds. In other words, low is fine at highway speeds, too.
Q: Given that the TMS maintain the battery within a fairly narrow range, why is the battery life less in the cold? I would think the TMS has to remove heat even in winter when I'm driving.
Larry Laws: Tthe battery efficiency is so high that it does not create enough self-heat to require the use of battery cooling in the wintertime.
Q: What tips do you recommend to get the most battery mileage out of each charge? Coasting as much as possible, fan only climate control, etc. Thanks!
Larry Laws: Check your tire inflation, keep the car in the garage, pre-condition your car when it is plugged in, maintain posted speeds and try to choose routes that have mostly flat surfaces. Good luck!
Q: With remote pre-heat (say, 15 minute before I go and pick up my car), how does the car know to what level to pre-heat the car? Let's say that I left the car with no heat "on" (all dials to zero fan, zero everything). Does the car "resume" the "pre-heat" to where it was left off when it was shut down the evening before, or is it to some other level?
Larry Laws: The car will pre-heat to whatever setting you last had.
Q: If the Volt is parked in the airport parking for a week in very cold weather. Will the battery be used to try to keep itself warm? And I come back with a depleted battery?
Larry Laws: No, the battery will not self-warm.
Q: After a full charge (on the 120v charger) my Volt shows fully charged but only 30 miles estimated EV range. How is the Volt calculating that I'll only get 30 miles EV range?
Larry Laws: The estimated range is based on our HVAC usage and kw/H you are using, along with outside conditions. Over time, the car essentially gets to know you and adjusts the number to line up with your driving style.
Q: Will start at -40 celcuis unplugged or if will I need to tow it in a heated garage?
Larry Laws: If the car soaks to that low of a temperature, you'll want to plug it in. It wouldn't have to be in a heated garage.
Q: How can we minimize how often the engine needs to run to warm the car and battery? Does pre-conditioning help with that? Does setting the climate control on ECO help with that?
Larry Laws: This doesn't sound intuitive, but if you want the engine to run less (this will use up the battery quicker), the electric heat in Comfort mode will keep the engine off more.
Q: I've found that the eco A/C had a minimal impact on mileage, I was easily getting 40+ miles on it. Eco heat is definitely using more electricity
Larry Laws: Yes, that's right - per amount of temperature change, it takes more energy to heat the car than it does to cool it.[PAGEBREAK]
Q: I noticed a similar dropoff in EV range in Sept. but it was also after a dealership drove it in Drive and didn't really try to save charge. I thought maybe it took a few charges to get back to normal. Things got a little better, but after the upgrade I still am having issues. When I call the Volt advisors they told me to completely discharge the battery and go to gas before recharging and do that 5 to 10 times. Do you know what that is about?
Larry Laws: Linda, after the upgrade, your EV range calculator was reset, so the car re-learned your driving pattern to recalculate your range. The cold temperatures now will also have some effect.
Q: What is the purpose of the 12-volt battery?
Larry Laws: We use the 12-volt battery to power up all the vehicle controllers before turning on the large lithium-ion battery.
Q: If I take my Volt to Florida this winter for four months and am only able to charge it once a week or less, any impact on battery life and range in the future when I get it back to a normal charging schedule?
Larry Laws: No, that shouldn't have any impact on range.
Q: When plugged will the car's heater run 100% on plug power or battery?
Larry Laws: It runs on plug power first and then battery power.
Q: When the battery gets depleted and the gas engine kicks in, does the Volt still use the electric heater to heat the car? Or does it circulate heat from the gas engine (like a conventional car)?
Larry Laws: The heat is mostly generated from the gas engine like a conventional car (and the electric heater is off), but sometimes to extend engine off at standstill, we will supplement with the electric heater to provide heat.
Q: Regarding the multiple Volt fires. It is being reported that the fires only occur after accidents, but that is untrue. The Mooresville, NC Volt burst into flames while charging, and had from all reports never been in an accident. Ditto the two cars that flamed out earlier this year. There have been stories with GM and government officials citing at times - the charging station, the charging cable, the battery itself and coolant leaking from the battery - as possible reasons for the fires. Given that you have as of yet no idea what the problem is, shouldn't GM halt production of the Volt, rather than up production to 60,000 as planned next year?
Larry Laws: You are misinformed regarding the Volt fires. There have been two house fires - one in Mooresville and one in Connecticut - both of which the Volt parked in the garage was ruled by the local fire marshals as not at fault.
Secondly, there have been some irresponsible media reports speculating on a whole variety of causes for the two fires which occurred weeks after tests (the first three weeks, the second one week). In both incidences the battery was ruptured during the test causing a coolant leak inside the battery pack. The vehicle (in the first incident) and the battery only (in the second incident) were then rotated 45 degrees every five minutes to simulate a rollover. We continue to work with NHTSA to determine the exact cause and the appropriate solution.
The Volt is a very safe. There have been no changes to the Volt's five star rating by NHTSA or its top safety pick given by the IIHS. And most importantly, there have been zero incidences.
Q: Is the 12-volt battery recharged from the high-volt battery? From the ICE or exclusively from 120/240v charger?
Larry Laws: The 12-volt battery is maintained by a DC to DC converter. Energy to maintain the 12-volt battery can come from any of those sources.
Q: I notice that when the gas engine comes on the heater starts putting out way more heat even though the controls are set to a certain temp. WHY?
Larry Laws: In actuality, the electric heater is not keeping up with the setting you have dialed in, so when the engine kicks in, it makes up the different to achieve the desired temperature.
Q: Does regen or normal-use use the cell balancers? Or only during charging?
Larry Laws: It's only during charging.
Q: Would I get more winter range if I charge my volt in the garage vs outside?
Larry Laws: Whatever is warmer. That will give you more range.
Thanks for the chat everybody. Great questions - wish I could have answered them all. If you have suggestions for future owner chats, let us know on our Facebook page or on www.ChevroletVoltAge.com. Thanks.
Click here for the most recent article on the Chevrolet Volt fires.