Prius Prime Plus in my hands

This was my original thought too. But as I was doing the 30 mph HV baseline, I noticed the HV part of the traction battery icon was slowly going down and then the engine came on. This suggests that at 30 mph, the car can dip into the HV battery range enough (or cool off enough?) that the engine will have to come on. In effect, the car will reach a steady state with engine cycling ON/OFF to maintain the minimum SOC or coolant temperature. It is something to investigate.

Bob Wilson

 

The metrics we need are:

• engine rpm
• engine mass air flow (for fuel consumption)
• MG1 torque
• MG1 amps
• traction battery Volts

Bob Wilson

 

We have so little freezing weather in North Alabama but 5:30 AM, it was 29F (-1.7C) so I did a warm-up test using HV mode:

• 1.2 mile @25 mph -> 29 MPG, 0.041 gal
• 9.2 mile @60-70 mph -> 48.8 MPG, 0.189 gal
  
• 10.4 mile (total) -> 45.2, 0.230 gal

If we have another freezing night, I can increase or decrease the first segment to get a better handle on the warm-up interval. In the past, it usually takes about 3 miles before the engine is warmed enough to become efficient. The earlier transmissions took 20 minutes.

Bob Wilson

 

A graphical history of a JuiceBox Pro 40:

• Up until 2017 the EVSE was at home and we only had a BMW i3-REx, maximum 31A.
• In 2017, the EVSE was at Propst where our BMW i3-REx, Prius Prime, and mystery cars could charge.

Bob Wilson

 

Ran out of gas again . . . on purpose:

1. Running car in hybrid mode, speeds 60-75 mph.
2. When "low fuel" light came on, reset trip meter and put in CHARGE mode.
3. With 30.6 miles @35.6 MPG, about 28 minutes, reached 80% SOC, burned 0.86 gallons of estimated 1 gallon remaining.
4. Car reverted to mixed EV-hybrid mode, put in hybrid mode and continued driving.
5. Got bored and drove to gas station: 49.4 miles @40.8 MPG, 84% SOC (leaving Interstate), filled 11.55 gallons

Lessons learned:

• +1 gallon gas remaining when "low fuel" light comes on
• CHARGE mode at 60-70 mph, reached 80% after 0.86 gallons
• +11.4 gallons in tank
• It is boring to try and run out of gas in a Prius Prime

All the 'hair on fire' DO NOT RUN OUT OF GAS critics . . . <YAWN>

Bob Wilson

 

About 28 minutes estimated on speed and distance covered. I wasn't trying to record the time, sorry. My impression is CHARGE mode appears to use the same rate more or less. What I remember:

• Left work in EV mode driving from 215 Wynn Drive, Huntsville AL to CIty Cafe, 101 1st Ave SE, Decatur, AL
• Ran out of EV charge around Huntsville-Madison Airport on I-565, switched to hybrid mode
• Gas warning light came on about 1/2 mile west of I-565 and I-65 interchange and turned on CHARGE mode
  
• Breakfast at City Cafe
• Returned to 215 Wynn Drive with ~75% SOC, 29.3 miles @36.2 MPG
• Joe hopped out and I tried to drive the car dry until I got bored and went to the gas station.

Bob Wilson

ps. Does the map help?

 

I was more interested in showing how the car works to our visiting tech, Joe, than precise and exact measurements. Since this was my third fill-up since January, it may take another two months before I can replicate the experiment with more precise metrics. <GRINS>

Bob Wilson

 

I have been worried about the Prime traction battery and heat. This afternoon it was 85F when I left work early to beat 'last call' at a 5-Points, 1892 bar and grill, and plugged in:

• A message popped up asking if it was "Ok to run the AC" - using the steering control, I was able to reply "OK"

It appears the car takes 3.3 kW and rests. It repeats this cycle until the traction battery finally is cool enough. Then the normal traction battery cooling proceeds. When I left, the car showed 98% SOC as the 'taper' charge had just started.

I am relieved that the car asked to use the AC. I'm not sure it really used it BUT this is better than the alternative.

Bob Wilson

 

The message showed up turning off the car when parked and battery drained and temperature 75-85F. Happened again this morning.

As for the graph, it appears the car is moderating the L2 charger operation. I had not seen that before so shared it here.

Warm and hot weather operation is something I am interested. In contrast our liquid cooled, BMW does it automatically.

Bob Wilson

 

RECOMMENDED DRIVING PROFILE ELECTRIC $/MILE << GASOLINE $/MILE

1. DO FULLY CHARGED AND FUELED
   
   1. Drive in EV (like a mad man!)
   2. Eat lunch or do chores where there is a free charger (EVSE)
   3. Plug-in at night
2. WHEN GAS MUST BE USED
   1. Enable when 10 miles or more must be driven regardless of EV level
3. WHEN GAS WARNING LIGHT COMES ON
   1. Put car in CHARGE mode until it shuts down (80% EV)
   2. Refuel when EV charge begins to descend (*)
4. END DO

RECOMMENDED DRIVING PROFILE GASOLINE $/MILE << ELECTRIC $/MILE

1. DO FULLY CHARGED AND FUELED
   1. Reach cruise speed in EV
   2. Switch to HV mode
2. WHEN GAS WARNING LIGHT COMES ON
   1. Put car in CHARGE mode until it shuts down (80% EV)
   2. Refuel when EV charge begins to descend (*)
3. END DO

* - If out of gas and traction battery SOC, the car will throw a "Power Steering" fault and coast down to a stop. If you have a spare can of gas or road-side service, you will have to do a 12V power-on, reset by disconnecting the negative battery terminal for about a minute. Record any vehicle trip meters before this happens as they will be lost.

Bob Wilson

 

Based on testing yesterday afternoon, I may revise this:

It is to spread the engine warm-up over a long enough distance to be in the 65-75 MPG range. If you run on gas for 1-2 miles, you'll see <40-45 MPG simply because we have to pay the gas warm-up price. NOTE: this assumes no traction battery charge which was not part of the earlier rule of thumb.

The goal is to avoid running the gas engine for just 2-5 miles, short distances, when the warm-up costs accumulate. So let me give two examples where the commuting distance is just beyond the traction battery range. We'll use EPA numbers, 25 mile EV range, for now on a 30 mile commute:

• 25 mile EV + 5 mile hybrid (~45 MPG)
• 20 mile EV + 10 mile hybrid (~65 MPG, warm-up averaged in with warm engine efficiency)

We have a prediction of colder weather later this week and I'll be investigating the ICE. The Prime is better than we'd seen in the Prius so I'll be doing more testing in this area.

Now there appears to be two warm-up methods:

• cold-soak startup in morning warm-up - traditional hybrid Prius mode, pretty inefficient with low MPG
  
• while at speed warm-up - this appears to be exceptionally efficient

Sorry for not being tighter in my descriptions but this is an area under investigation. But the rule of thumb remains that we want warm-up miles to be very much smaller than gas miles on a warmed drive train which includes the engine. If possible, we want warm-up miles to be while moving initially using EV power to get to speed.

Bob Wilson