New 21 Prime limited commute strategy

You can switch back to EV but you need to wait until the ICE warms up. Several minutes depending on outside temperature.

 

Already answered by others. Do you have charging capability at work?

 

With the use of 25-35miles EV range on both ways, if you can limit the 50 miles hwy drive speed, you should be able to get over 100 mpg. Try to use up all EV range before reaching work or home but also try not to let the engine go through the "warm-up" cycle more than once.

 

I took a new route today to my weekly meeting and it was from home rather than the office. It's a 40+ mile round trip from home.

To be different, I started in HV on the Prime and took SR 54 which is 50-60 mph with typically about a dozen stops over the part I drove today. I stayed in HV for the first roughly 11 miles which got me off that road and a little ways on the next road which is a little slower with no stops for several miles. At that point I switched to EV the rest of the way. For that initial HV part I showed 60 mpg. The rest of the trip in EV was 5.7 m/kWh and I got home with 1.1 miles of EV left. A pretty good guess on the timing going to EV.

That comes to about 0.17 gallons ($0.40 locally) and $0.60 worth of electricity. Roughly $1.00 to go about 41 miles = 2-1/2 cents/mile.

 

I think you are confusing the part-time EV icon indicating the typical battery-run in HV mode with full-time EV mode. Perhaps what caused the confusion is also the fact that the Prime (as opposed to the regular Prius) is able to run off of the battery even past 42MPH, and you likely had the somewhat fluid HV portion of the traction battery pretty full when you got off the interstate resulting in a longer battery/EV run (as part of HV mode still) than usual.

 

When you are in hybrid mode and accelerating slowly, the traction battery will provide the power needed to move the car. If you had accelerated more aggressively it would have kicked in the ICE to supplement the electric motors.

This behavior goes all the way back to the first Prius hybrids. In the 2002 models you could use the gas pedal gently to stay on battery only as you go from 0 to 25 MPH in about the length of a city block.

On your car, the 0% battery is the EV portion of the battery. The car reserves the last XXX percent of the battery for Hybrid mode.

Dan

 

It might help to put it in perspective this way. You did not go 10 miles on battery. The ICE was called upon when you encountered a grade and some of that power was fed back to the battery. The first 27(?) miles on EV would have included grades and acceleration.

In general, the Prius does a good job of maximizing energy usage while minimizing emissions without any conscious efforts on the part of the driver. Since you will be able to charge at work, you will probably find that there is not a lot of difference between using the EV up front or using only when you are not on the highway. My 2002 Prius used to irk me because the engine would heat up for 5 minutes or more as soon as you started the car. But the first 5 minutes of my daily commute was stop signs, cross traffic and traffic signals. That was 5 minutes of idling even though I had a full battery. Ironically it would finish heating up just as I got to the freeway.

If I were you I'd stop worrying about it. It's working as designed.

Dan

 

When you do your test, make sure to include an altimeter so you can see the subtle down slopes that allow you to coast without realizing it.

I'm no longer an engineer, but I'd start with whatever design documentation that can be found. Everything else should trace back to the designer's intentions. Design requirements that I recall hearing about:
1) A percentage of the total battery capacity is reserved to avoid overcharging/overheating.
2) A percentage of the remaining capacity is reserved to avoid over discharge.
3) The "100%" on your dashboard really represents amount reserved for EV.
4) The little battery graphic shows the "hybrid buffer" which should be the capacity not accounted for in 1-3.

A good tool to use is Dr Prius which use an ODBII reader to give you the voltages of the battery.

While you think that you are getting 10 miles of EV after the battery is depleted, I see that you are using the buffer that is normally used in HV mode to allow the battery to supplement the ICE. That buffer appears to be more generous than I thought it would be.

In the original Prius design, (2000-2003) the battery was only 1.778 kWh. In that design the battery pack is normally charged between 40–60% of maximum capacity to prolong battery life as well as allow headroom for regenerative braking. Even so, I have traveled across town on battery power alone when the battery was fully charged. The more lights I hit the more likely I was to trigger the use of ICE.

Dan

 

@dbstoo makes an excellent point. I was going to ask about the slope. Even a nearly imperceptible downslope combined with lower speeds in the 30-40 mph range will produce prodigious miles/kWh numbers. Try taking that route again where you got the seemingly impossible EV distance in HV mode but make sure you have some EV range available so you can stay in EV mode (as opposed to HV with ICE off). Then watch the m/kWh gauge next to the speedometer. (If you don't have that enabled, it's in the meter customization screen in your MID settings.)

By way of explanation, if you had time to brake gradually enough to keep the friction brakes out of play until the end of deceleration, slowing from 75 mph to a stop will regenerate over a mile of EV range and maybe more from that speed. Not enough to enable selecting EV mode, but enough to keep the ICE off for quite a while. Combine that with how far into the HV part of the battery the Prime can go before starting the ICE along with possibly a slight downward grade and it can astound you. I'm an engineer too (electronics) and former industrial electrician. And even for me, this car sometimes comes really close to being magical the way it can conserve energy.

 

@dbstoo and @jerrymildred have done an excellent job trying to explain it. As they explain, it seems that the larger HV battery buffer (as compared to the regular Prius) being enough for the limited charge draw needed to go the 10 miles with likely a slight down grade, likely explains it. I still see value in limiting the battery to non-highway use since, per Toyota, one way to minimize battery degradation is to not use it at high speeds (perhaps they are talking 80+, but nonetheless).