Energy Consumption

The Engine running due to temp occurs when outside temp is < 25F and with temp belo 25, the engine restarts when Coolant is < 105F, and runs until the engine coolant is ~ 150F. It switches to CS mode so the generator is running and the car is approximately trying to maintain battery level, while using it as a buffer. (I'd expect the implementation is some sensors sensing the need and then changing the minimum SOC in the car's control logic to the current level, thus initiating CS mode).

Because the starts are cold the MPG_CS is horrible, especially if there is much of a load. Because the ICE shuts off as soon as it gets hot, it never really does catch up to allow better. I've had runs were I get 30mpg_cs from it in cold starts but that may be because I was going more down hill so there was very little load needed. Switching to MM may help efficency in mpg_cs, though it would mean you likely arrive home with excess charge (unless your trip is so long it needs CS mode). MM mode would get it hotter but still likely that it will cool sufficiently to need to restart.

If you use comfort mode for heating after the ICE runs, it will decrease the frequency of ICE running as the engine block retains more of its heat (your not sucking it off for heating the cabin). It will, of course, use more battery to generate heat in comfort mode, but if you have the electrons to spare it will reduce gas consumption.

You might find the following threads at GM-volt.com interesting
http://gm-volt.com/forum/showthread.php?8210-Volt-Engine-Operation-in-Cold-Ambient-Temperatures
http://gm-volt.com/forum/showthread...25km-arrived-with-38km-EV-range.-Great....not!
http://gm-volt.com/forum/showthread...-radiator-and-save-ICE-heat-for-cabin-heating

http://gm-volt.com/forum/showthread.php?10786-Reasons-beside-heater-batt_TMS-4-lower-winter-EV-range

http://gm-volt.com/forum/showthread.php?10879-Super-cold-day-16C-Range-held-up-well

 

A bit of off-topic from the energy consumption topic but I just want to point out the tailpipe emission caused by those ULEV rated ICE restarts.

PiP prototype finishes the cycle in 42 seconds and still achieve SULEV - thanks to the exhaust heat recovery system and clever optimization.

We have yet to find out the emission of the SULEV Volt version that is coming out (only in CA?). PiP could use the superior warmup cycle because it could be doing that more often.

 

That's not an EREV operation but a hybrid operation.

The idea of EREV was to use the gas engine when the battery energy was no longer available. Here, you still have energy in the battery yet gasoline was used to assist. Volt is not an EV the first 35 miles. This is clearly a hybrid operation.

 

I wouldn't even call it hybrid at that point, the ICE was running regardless of load to generate heat (even stopped at lights). I'd just call it classic ICE operation, like they turned the hybrid off (sort of the evil opposite of the EV-city button on European PiP's).

That said it doesn't bother me that it chooses to forego the design brief to provide better TMS for the battery and preserve battery life, I would prefer it to work this way than just keep a second gas car around for use on those days.

The tools are available, might as well use them. Its pretty much the whole point of the PiP blending gas. I think what most people would prefer is the ability to control mode, so I can make it stay EV if I know I'll reach my next charging opportunity before I need to burn gas, or choose to run the ICE when the heat source would be most needed.

 

Well that is what I do not get. Like yesterday when my engine came on due to temps (it was 23 outside) and I got 14mpg for that stint.. It seemed to me the car was not utilizing the engine to power the car, BUT was using the battery power to do so as it barely changed my energy consumption at all. The sole reason of the engine coming on is to heat up the electrolyte in the li-ion to get the electricity flowing better and to provide supplemental heat to the cabin (although I did not notice any positive heating effect inside).. It just drove my usual $0.032/mi cost to almost $0.06/mi! Temp outside today was good though so all electric cruising for me hopefully for the rest of the month. It was about time for my car to run maintenance mode anyway, so figured why not burn it for a reason.

 

Yea, if the gas engine come on, I would expect the electricity consumption from the battery to go down.

I guess Volt is making sure the gas engine is used only to warm up the battery and for the cabin heat. Idling the gas engine for no other purpose seem like a waste of resource.

Perhaps, it had to be done to avoid patent lawsuit from Toyota.

 

RoadBurner, saying 14 mpg does not tell the entire story. The petrol consumption may have been quite low, but at low efficiency. I'd just chalk it up to GM's preoccupation with the Volt being an "EV", even in cold weather. Was the ICE noise muted ?

As for the high energy consumption/mile, welcome to the winter in an EV. Not only does an EV pay all the winter penalties like every other car, it pays straight out of battery for cabin heating too.

 

My observation in my situation was battery depletion did stop while the ICE was on, gauges even switched to blue CS read outs.