2010 Model disappointing to me

I haven't seen anything to the contrary so I'm going to assume that the EV and Econ buttons do the same things on the G3 as they do on the current HH.

If you engage the EV then the ICE is blocked from firing. There are two limitations. The speed has to be less than 25 mph and the traction battery has to have sufficient charge. Normally you cannot engage it first thing in the AM.

The ECON button can be engaged at any speed. It desensitizesthe gas pedal and makes the vehicle feel like it has no guts. Can't get out of its own way. It can be clicked 'off' at any time as the need arises.

 

Certainly isn't on NHW20 'Iconic' Prius, and I would hope it wouldn't be. The reflective* speedometer/shift indicator/odometer display is on the right-hand side of the dash. I grant you that the slot in the dash is probably the same, so that one moulding might be identical, but I can't see it saving very much money. It isn't - the speedo and immediate surrounds are taller than the part that stretches over to the passenger side for the passenger seatbelt idiot light. The 2010 also looks to be asymmetric.

The ECUs and junction blocks in the passenger compartment swap sides, as does the air conditioner - the cabin air filter is still behind the glovebox on the left-hand side of the car, and the main 'passenger side' junction box is still by the driver's knee, so the driver can hear the indicator relay ticking.

Actually, in a few places, it looks to me like the car betrays its right-hand-drive origins. The placement of the power button is far better on the RHD version (below the right-most vent).

* Not sure what to call it. The speedo is projected from below the dash onto a mirror so it looks visually further away than the idiot lights surrounding that screen. It looked from the video of the new steering wheel touch indicators that this is still present on the 2010 car.

 

This is what I hoped the eco setting would do. But I gather from Toyota's features description that it does not. That is why I was disappointed in the feature.

However, it's a moot point for me, since the car overall does not seem enough of an improvement for me to trade in my excellent 2004 Prius.

 

I suspect they are one and the same. Shifting the performance curves amounts to desensitizing the go pedal, from a user standpoint. Whether the curves are modified or merely shifted is something we will have to find out at a later date.

Tom

 

In the Prius (at least pre 2010) you can EV to 32 MPH. It WILL engage first thing in the morning IF it isn't too cold. 75F no problem. 25F? NO WAY! Not even if the engine is at operating temp.

Well I'll be, I managed to get into EV at 18F this morning. 6 blue bars, engine warmed up.


I think there are other factors as well, including battery SOC and temp.

 

I'm pretty sure the 2004 Prius can be put into EV mode regardless of ambient temperature, if it is done before the engine fires. However, at low temperatures a lighter pressure on the accelerator will cause the engine to come on. At warmer temperatures the car will allow more accelerator in EV mode. The exception may be if the battery temperature is too high (as it can easily be after hard use on a hot day).

With the engine at operating temperature, I have used EV at 20 degrees Fahrenheit below zero. But if the heater is on, everything must be warmer before EV will engage.

If the heater is turned on, then EV will not engage first thing cold on a cold day. Asking for heat and asking a cold engine not to start are contradictory, and the Prius will obey the request for heat above a request to keep the ICE off.

 

P.S. One of the great annoyances to me is that while the Prius will go electric up to 42 mph, that limit is reduced to 34 mph if electric is engaged via the EV switch. I see no reason for that discrepancy, and it's unfortunate that they (apparently) have not changed this in the 2010 model.

Another great annoyance which I gather (?) they have not changed, is the need for the car to stop for 10 seconds after reaching operating temperature, before it will go into Stage-4 operation. I see no reason why it should not go into S-4 operation as soon as it reaches the requisite temperature.

 

The Battery ECU sets two parameters, CCL (current charge limit) and CDL (current discharge limit) based on a number of factors including the temperature of the battery itself and SOC. If the battery is too cold or too hot these values will be reduced to more or less zero. This is done to protect the battery, which can be easily damaged by current flow under these extreme conditions. The HV ECU uses these values as part of its decision process regarding how much power to request from which source. As these values move around, they will affect how easy it is to get into stealth / warp stealth, and once you are in these modes current exceeding CDL is one factor that kicks you out and starts the ICE. For these reasons PHEV conversion displays like the CAN-View often monitor both your Amp draw, and the current CCL/CDL values so you can stay all electric as much as possible.

As I understand it (although my understanding is fuzzier here), EV mode sets CDL fairly high if various other conditions are met. The same thing basically happens if SOC is around 74%, where CDL naturally maxes out. Many PHEV conversions either try to maintain, or spoof an SOC around this value, to maximize electric use. This is one reason why EV mode is often of less use on a PHEV. If the CDL is high anyway, then you have EV mode like all electric acceleration capabilities, without the EV mode speed limit. There are times other than current > CDL that can cause the ICE to start, and EV mode can block some of these, so there is still some utility perhaps.

Rob

 

But the computer can kick you out of EV mode any time it likes. Most notably, stepping too hard on the accelerator while in EV mode will start the ICE. And I have very definitely observed that when the ambient temperature and the battery are cold, the computer will tolerate much less accelerator in EV mode.

In other words, it already does limit current draw dynamically in EV mode. There is no need to put a lower speed limit on EV mode than on computer-initiated electric mode, because the computer can use actual physical conditions (temperatures, current draws, etc.) to drop out of EV mode.

What happens therefore, is that there are times (all too often!!!) when the car is warm enough for S-4 operation, and the battery SOC has gone to 7 green bars, but the car refuses to shut off the ICE because traffic conditions have not permitted me to stop for 10 seconds; yet I cannot use EV mode because my speed (again, following traffic) is in the 35 to 40 mph range. This is frustrating, and results from the confluence of two unnecessary engineering decisions.

This is probably my biggest quarrel with the 2004. Fortunately, it's much less of an issue for me now, since I drive the Prius so seldom. But their failure to correct these problems in the 2010 is a disappointment for me. These problems of course do not exist with my Xebra, which is all electric all the time.

 

This is a total guess, but I wonder if the boost converter in the inverter kicks in around 34mph? The boost converter converts the battery's native ~220V up to ~500V in order to overcome the motor's rising back EMF (self generated voltage) with rising rpm. This was one of the major design improvements over the Gen 1 design. This allows the electric motor to be used at higher speeds/rpms, but the current into the motor is divided down by the same ratio as the voltage is multiplied up, so there is much less current available to the motor. Its the same idea as a gear reduction or multiplication, where the product of torque and speed are constant, one is multiplied by the gear ratio, the other divided.

These aren't real numbers, but lets just make some up as an example to illustrate. At 0 mph/rpm lets say the inverter/battery is putting 100A into the motor at 220V. We're putting 22kW of power into the motor, and ideally we'd be putting 22kW of power on the road. Now lets say that at 34mph, the rpm of the motor is such that the back EMF is 220V. We have to subtract this from the Inverter's output voltage, which is also 220V, so the net output is 0V. Even if we were still able to dump in 100A (which we probably can't) the power delivered would still be 100A * 0V, or 0kW. That means, the battery is still putting out 220V*100A = 22kW, but 0kW is reaching the road, efficiency has fallen to 0%. Without the boost converter, that would be the maximum speed at which we could have any electric drive. With the boost converter, we can boost up the inverter output voltage to 500V, but the output current falls to 44A. Now our power delivered to the motor (and ideally the road) is 500V-220V (back EMF) = 280V * 44A = 12.3kW. We're still pulling 100A * 220V or 22kW from the battery, so our efficiency is about 50%. Not great, but better than 0. As you continue to go up in speed / rpm, the back EMF from the motor will continue to rise, and at some point power delivery and efficiency will fall back to 0. We know this is at least 50-60mph, as those are the max speeds that have been achieved on all electric with PHEV experiments. This is not the 0 power point, just the point at which the motor output power matches the power required to continue moving the vehicle at that speed. The 0 point must be over 70, as I know I've gone into warp stealth on long downhill highway runs at speeds over 70. We also can assume that they wouldn't really wait for the output power to drop to 0. There would be some crossover point where the power output and efficiency with the boost converter (despite it having some losses not considered above) would be greater than that without.

So if I had to guess, this is why there is an EV limit. As the efficiency drops, you are spending more and more battery energy to get less and less power to the wheels. At some point its just not worth it. The only time it might be worthwhile is when the battery SOC is very high, and the HV controller wants to burn off power to bring the SOC down to nominal. Then it doesn't care so much about efficiency, as it just wants to get rid of charge. That would explain why the controller lets you use electric in Warp Stealth, or ICE Spin or Super Highway Mode (whatever the right term is for electric drive over 34 or 42mph?) at higher speeds when the SOC is in the green.

IMHO its not so much Toyota being arbitrary, its just physics. Sound plausible?

Rob

 

Your guess is as good as mine on problem getting into S4. I'm vaguely familiar with the concept, but don't have a scan gauge. I've rarely had the problem of not being able to get the ICE to shut down and get into glide mode after 1-2 minutes, but I think most of that is a product of my warm climate and/or driving conditions. Once I get to work on my PHEV conversion and get a CAN monitor in place, I hope to learn more about this aspect of the Prius's operation so as to make the most of the conversion.

Rob

 

My guess is your battery was too hot then.
It is necessary to offer the battery warranty.

Ken@Japan

 

I thought the HSD always operates at the higher (~500 v) voltage. Regardless, this does not explain why the limits are different for computer-initiated electric mode and driver-initiated EV mode.

Nope. It commonly happened on my drive to work in winter in North Dakota. Note that the car happily went into EV mode, once warmed up, but when I initiate EV mode the speed limit is 34 mph. If I pulled off the road and waited for 10 seconds, then it would go into stage-4 and go electric on its own, with a limit of 42 mph. But without the ten-second stop it would not. To my mind, there is no reason to require the ten-second stop! Why not let it just go into stage-4 when all the conditions are right? Why is the ten-second stop required? And why have different speed limits? If conditions allow electric driving, why not have the same limits? The car can still exit electric mode whenever conditions no longer permit.

The biggest problem in North Dakota was in winter, where the battery would stay at 7 or 8 bars because the car would so seldom get a chance to go into s-4 on my commute. (People with different traffic conditions, who were forced to stop for traffic lights, did get into s-4 and all was well. But that irrational 10-second requirement often prevented mine from doing so. I could emulate it once I got the aftermarket EV switch, but then I was hit by the lower speed limit of 34 mph rather than 42.)

It's not a real issue for me anymore, because my Prius no longer makes those shorter trips. Now I drive my EV for anything up to about 35 miles, and the Prius only makes longer trips, usually on the freeway, where none of the above is an issue. But I still think these are design shortcomings, and I'd love to hear an explanation for why the 10-second stop is needed.

Did anybody at PCD ask that question?

 

The factory-fitted EV mode is capped at 29mph in the UK-spec Prius. This may be a conscious decision to stay under the UK's 30mph default urban speed limit (if no signs indicate otherwise and in a built-up environment, with street lights, the limit is 30mph) and Europe's similar 50km/h limits.

34mph is a little under 55km/h - Japan's general speed limit is 60km/h.

So there could well be a regulatory, type-approval reason why they would have to keep it below specific limits if the engine were not allowed to start.

My car doesn't seem to need 10 seconds stopped to go into S4. If the conditions are right it will turn the engine off when you lift off the accelerator pedal enough to get a small amount of regen - applying the accelerator gently is enough to get a glide. If it won't switch the engine off, either the engine isn't warm enough, the battery isn't charged enough (or warm enough/too warm), the car hasn't reached the temperature set on HVAC, or the electrical demand is too high. In that case it will usually switch off when put in Park at a light.

 

I agree. If a 10 second stop sets some controller to allow auto EV, the engine is already up to the required temp. In the fall and spring I drive about .75 miles, then hang at the stop sign (if there is no other traffic which I would hold up) until the ICE shuts down. I can then auto EV down the hill, get to ~35 MPH, and glide the next half mile dropping to about 32. From there, I can auto EV the next .3 mile until the slope demands the ICE. And another 3 miles on, I can EV another .5 miles on a flat. If there is traffic, no 10 second stop, ICE runs the whole distance and bye-bye 99.9 MPG in those sections.

In the winter, when I need heat, I don't even bother with the 10 second stop. Even with the block heater and 75% grill blocking, a low ambient temp will not allow me to get into stage for for several more miles.

In summer, a normal stop at the stop sign will allow auto EV.

 

Not necessarily, the ICE kicks in as soon as you pass the magic MPH number gliding down hill. I have an area on my commute home from work where I force EV on a small up slope on a 30 MPG road which Tees into a 40 MPH road. If the light is green, I could continue on the 40 MPH road in EV since it is a slight down slope and the car will auto EV there but the forced EV cutoff precludes this. The ICE kicks and runs the requisite time before dropping into auto EV. As Daniel said, it need not do so!!

 

I'm pretty sure they don't use the boost converter at low rpms, as its more efficient without it. There are losses associated with the conversion, so as long as the back EMF is low, you're better off putting in more current at the native voltage.

I disagree. The HV controllers job in life is to decide how to mix ICE power and electric power to maximize efficiency. This mandate is second only to its prime directive, "do not allow any harm to come to the battery or motors." The argument presented above provides, I believe, a plausible explanation for why using electric drive above a certain speed would be fairly or even very inefficient. As long as SOC is ok, temps are ok etc, the HV controller humors the driver by allowing him to request EV mode. However it draws the line at operating in this mode above some minimum threshold of efficiency. My guess would be that this this threshold is determined by the driving patterns expected in the target market, hence different speeds for different markets. When SOC gets above 72% or so, the "Prime Directive" takes over, and the HV controller allows the driver to use more electric power at higher speeds despite the inefficiency in order to reduce the charge level of the battery.

I don't know that this is the actual answer, but it makes sense to me

Lets also not forget that I believe Toyota's intended use for EV mode was to move the car across a parking lot without the ICE starting (don't they even call it "ICE warmup delay"), rather than for optimizing mpgs on your commute

Rob