Gen3 PHEV optimum mpg is all about HEAT

Good work and write up Dan, so its all about regulating engine temps.... The more heat the better, engine stays off. How does the Phev work on the highway, and does the battery last the life time of the car? I look on their website and it's 2k for the kit right? I do mostly highway commute I wonder if I should invest in one? Does it give u a boost in power on the low end? I find it hard for me to stay in EV mode on the streets. Are you happy with the kit?

Sorry for all the questions, I've never heard of this until your post. Thanks again for any feedback... Brandon

 

At the extremes of hot and cold, the temps, "heat," of the HV battery, or
batteries, will also have a negative MPG effect.

At the cold end, the batteries are slow to discharge/recharge until they
reach maybe 45 or 50 degF -- after a night-long winter night "cold soak."

On the hot end, oh, maybe 100 degF, the batteries have reduced
capacity -- after a long "hot soak" in an uncovered summer parking lot.

In both cases, propulsion will require more ICE power and reduced MPGs
until the HV battery/batteries are stabilized at "normal" temps.

IIRC, the Nissan Leaf monitors the battery temps during charging
and heats/cools its batteries as needed to provide full power at least on
initial start up.

 

Hi Dan,

Have you tried driving with the heater / defroster on yourself? I would recommend trying to drive the vehicle with said heater on and see how it impacts your known mileage. I suspect you'll find that driving habits play a more significant role in mileage results as you touched on in your other thread.

Heat certainly plays into how often the Prius uses the gasoline engine, but it also has a lot to do with acceleration speed and how accustomed you are to doing simple things like backing off the pedal
and reapplying pressure to turn the engine off.

The new Gen3 Prius warms up much faster than the Gen2 because it recirculates the exhaust (no more coolant thermos). It's also more efficient at lower RPMs than the Gen2 was due to the new engine (so the heater usage shouldn't impact mileage as much on the Gen3 as on the Gen2 in other words).

I assume when you say "driving it as a normal car" you are referring to more normal pedal acceleration speed as well?

EDIT:
Battery efficiency is also directly impacted by temperature as well--I agree with Rokeby on that point. The question is how much of a temperature swing is there on your batteries. For Nickle metal hydride there is a pretty big efficiency dip when it's cold. The same is true for Lithium, though typically not as bad (can't say for sure on the batteries you have, all chemistries are different).

The vehicle limits how much power goes in and out of the batteries when it's cold--for example, driving the car when the batteries are around 0F, you are basically driving purely with the gasoline engine since the wattage out goes effectively to zero. Typically it starts to decrease around 65F.

Andrew

 

Dan,

I don't think that we're at odds here. I acknowledge that what you've
said fits nicely with what is know about the HSD operating algorithms.

Once the ICE kicks on, the HSD keeps an eye on ICE and catalytic
converter temps and will as necessary run the ICE apparently solely
for the reason of keeping those temps up. While the Enginer system
does not do any active spoofing, the additional HV power does create
conditions, extended running as an EV, where the ICE and CC temps
would fall below the HSD-set lower limits and the ICE kicks on. All this
is fine and well.

The basis or my earlier post is that environmental conditions -- they
can be simplified to the ambient temperatures in the cabin and HV
battery box -- affect the HV battery. I did not mean to imply that
temps in your HV batteries have a direct affect on each other.

After a night-long cold soak at 0 degF it can take 30 miles to get the
HV battery up to normal temps. This has a direct affect on MPGs seen
during the period.

Not to take this into mind would lead to a belief that the ICE had a
problem... not so. (The HSD takes an active role is raising the Prius
HV battery temps. It tries to raise the SOC to ~65%, and uses lots
of small discharges and charges to heat the battery internally.)

It sounds like you are doing a great job wringing the best FE/MPGs out
of your Enginer augmented Gen III. Well done... :rockon:

I'm more than a little envious, I can only just barely hold 50 MPG as a
year 'round average on my Gen II. Such is life.

 

Dan,

ICE temp is very critical to MPG. I have learned over the last 6 months with the Enginer System is that during my nightly commute home which is mostly EV mode for about 35 miles. My coolant temp can drop to about 100F and if I am not light on the pedal the ICE will start up. It will keep running until it reaches about 130F and then I have EV mode until 45mph. I am planning to do some grill blocking next winter. For now I have adapted my driving to monitor coolant temps also since springs is here in So. Calif. Someone, I think Ken(from Japan) did post up a schematic of a device to trick the ECU on the coolant temps with a variable resistor but I am not too clear.

-Chan

 

*sigh*, Sorry Dan I didn't mean to touch a nerve again but there's no need to get upset. All I'm saying is that I believe the driver aspect (pedal behavior more specifically) is more important than the ICE temperature. An easy way to determine this would be to plot your own MPG averages with and without the heater on for similar (ideally the same) drives. This would establish your driving style and habits as a control environment and thus show how much of a factor said engine temperature actually is (obviously you must let the ICE cool off equally between runs or else it will invalidate the results).

I don't think anyone--myself especially included--will dispute the fact that ICE temperature plays heavily into maximizing mileage.

The title of the thread makes it sound like getting best mileage is entirely dependent on the ICE temperature but I disagree--I think it much more depends on the drivers individual habits and routines than anything else (within reason of course). This is all that I am suggesting.

Andrew