To Drain the Traction Battery or To Not Drain the Traction Battery? That is the question.

Really interesting guys, thanks a lot. I didn't know about the Atkinson Cycle

 

You are incorrect. If you drive in city, there will be less boost from electric motors during low speed acceleration or low speed driving due to low SOC. Meaning ICE will be forced to work harder/longer during those low efficiency states. I had a glimpse of that when battery overheated once and there was no battery boost for the rest of the trip. MPG plummeted to low 40's.

 

One of my methods of operation is to drain the battery using EV on my way home, because I know that when I start up again in the morning, the engine is going to automatically run and re-charge the battery. This is going to occur especially in cooler weather, whatever the charge in the battery is upon startup, until the engine reaches operating temperature. So it doesn't really matter what the SOC is when you turn off the car the night before, because it will be re-charged.

I don't know if all of these assumptions are correct but it seems to work for me. Any comments are welcomed!

 

The concern with this approach is that for the first few minutes the primary drive power is from the EV battery and the ICE mainly running to warm up the emissions system. So once the engine is online to power the drive wheels you will be running at reduced efficiency because some of the engine power will be allocated to recharging the EV battery which is now deeply discharged.

I will not claim to be 100% correct here but I have observed these conditions on my non-PIP using scangauge.

Could you simply use a modified pulse & glide strategy for that last couple of miles of your trip?

 

I do that to within about 3/4 mile to my house then I try to use as much EV as I can. I pick up an extra 1-1.5 mpg doing this in my development. Usually I end up with about 1 bar below half on the battery. In the morning I drive the car normally to the first light which is probably about .8 miles. When it's colder (below 45*) it's like clockwork that my engine temp gets to 104* and the EV symbol pops up while I am waiting for the light. EV is really not usable at that point. I go about another 1/2 mile driving normally and then get on the highway where I am forced to accelerate fairly briskly using the engine.

During the next 3/4 mile I have to maneuver over to the HOV lane. From that point on unless there is someone on my a$$, I use various techniques on the highway. I go 35 miles total to work and am usually in the 58-61 mpg neighborhood this time of year on Long Island. It has definitely been colder this year than usual.

Coming home, I take a flatter route and get about 62-67 (67 was wind aided) mpg. This is due to the fact that when I hit traffic I crawl along with the EV button depressed. The last 9 miles of highway I'm not able to increase my mpg since the concrete pavement is coarser. As soon as I get off and get back to secondary asphalt roads for about 2 miles, my mpg increases by about 3 using the techniques described above. Best I ever got coming home was 72 mpg (traffic aided).