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Discussion Starter #1
Recall that I was on a mission to understand why the Bolt bar chart screen has the red average line at the wrong place (as much as 2000% wrong). I was able to get through to senior Bolt engineers and we had a conference call about this yesterday. I am still digesting it. First they helpfully answered some questions I had that have been raised on this Forum several times.

1. It is ok to drive in N rather than simulating N by feathering the accelerator to have 0 energy. There is no lubrication of anything that depends on not being in N. My point: It is easier to be in N in certain situations than to concentrate hard on using the acc. pedal to simulate it. Good.

2. Hilltop Reserve is great for those on hills (like me). But if you are not, there is no reason to use it. Charging the battery to full each time is perfectly reasonable and will not affect the life of the battery. They have done many tests because of the warranty, and it is set up to be used in the obvious way. Good.

3. As for my pet peeve: They were well aware of the issue. They did it deliberately for this reason: Drivers are used to seeing an average line at the average of the bars. If they put the average somewhere else (like at the correct average value) it would confuse the driver and take attention away from driving. So they placed it at the place where they thought it would be somewhat useful (the average of the 5-mile averages) even though they knew it was the wrong answer, sometimes very wrong. Of course, the problem is in the scale: the red line would be illegible often if placed at the right place (because of the 252 that often arises: the "MPG singularity").

My view: Why place it anywhere? We don't need a line. We need a number that says: Average for the X miles is 4.2 mi/kWh.

I am still trying to wrap my head as to why they would include the line at the wrong place. Such an attitude to accuracy in the mechanical part of the car is unacceptable. Why is it acceptable here? I don't get it. The engineers did say they would look at my suggestions carefully and -- perhaps -- there would be a change in future. In the meantime, I have to switch to metric and see if the line is below 15.5 in order to know whether I am above 4 mi/kWh.

I am now in the awkward position of writing a paper inspired by this screen issue. That paper has grown quite a bit -- eg, I just learned of a huge unintended consequence (the "MPG Paradox") of the CAFE standards whereas a company that makes more fuel efficient vehicles can have their CAFE penalty rise instead of fall as intended. It is because of a misguided use of MPG by NHTSA. This was the last straw for me and I have now changed my personal view on MPG vs. GPM. I used to think MPG was fine if used properly. But while MPG is not going away, and it does have its place, this CAFE error (among other things) has convinced me that GPM is far superior as the primary method of measurement.

My current problem is that there is no way to describe the erroneous Bolt screen in my paper without saying exactly what GM did and why. Their main rationale is that they want the driving experience to be as similar as possible to standard driving.

If any of you want to see my paper, which will be finished in a week or so, send me a PM with your e-address and I will put you on my mailing list. Or I will post it on the web and add the link to this thread when it is finished.

I was impressed and pleased that they took the time to talk to me. They know exactly what they are doing and it was not an arithmetical error on the part of a programmer. That is the only bright spot here. I can only hope that they will ponder the situation and rethink their rationale for giving drivers very wrong data.
 

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What I love about the CAFE standards is that they measure the sq footage under a car at the wheels and bigger cars are permitted to get less gas mileage.... so poof in the 1990's all the automakers started pushing design changes that moved the wheels to the corners of the cars, for better handling of course!

Please send your paper to me...
 

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Great to here coasting in Neutral is safe. Distressing to hear they were OK with giving us worthless information, so long as it seemed familiar. :-(

Glad to hear they are so confident in the battery. Too bad that isn't reflected in the warranty. I will continue to use hilltop level, except for long trips.
 

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Discussion Starter #4
I guess your are referring to the warranty being 100000 miles or 8 years, but the warranty will come into play only if it degrades to 60% of original. I guess we do not know if it will really degrade that much (a 10% loss is acceptable I suppose; 30% seems like too much). There is essentially no downside to using Hilltop Reserve and I think they admitted that it could cause a very small decrease in the degradation, so no reason not to use it when you are not facing a 200+ mile trip the next day.
 

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There is essentially no downside to using Hilltop Reserve and I think they admitted that it could cause a very small decrease in the degradation, so no reason not to use it when you are not facing a 200+ mile trip the next day.
This statement is a little confusing because in your original post it states:
Charging the battery to full each time is perfectly reasonable and will not affect the life of the battery.
So did GM state that continually charging to full can cause degradation in battery life?
 

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Discussion Starter #6
I believe a very short comment by one of them (sometimes people speak at the same time) was to the effect that there could be very small degradation with full charging. But the much stronger comment that I heard was that they have designed the battery controller (and the warranty) so that filling to full is the appropriate behavior. So as to the exact meaning of the word "small" -- I cannot say. I might have pressed on the point, except that (a) I live on a hill so will always use the Reserve, and (b) there is essentially no downside in using the Reserve. My reading of posts on this subject is that battery experts would say it is better to have the batter at Y% instead of X% whenever 50<Y<X.

I note that 40% degradation over 100000 miles does seem excessive. But will that actually happen? I had a 2005 Prius with 110000 miles when sold and a 2013 Plug-in Prius with 56000 when traded-in for Bolt. I cannot measure the degradation in those batteries, but there was no detectable degradation.
 

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I owned a 2005 Prius and it had 350K miles when it was retired. I've rebuilt those battery packs and there was a loss in capacity but the BMS, as well as the battery type, is much different than the bolt. Using a fan to cool the battery wasn't good at all, especially for those living in warmer climates or on hot days.

Back to the Bolt - Even if it the degradation is 2%, 5%, etc, it would seem beneficial to not fully charge so the battery life can be extended. This topic has been debated numerous times with people on both sides of the argument.
 

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So glad to learn that you had a conference call with some of the engineering team. We are in the very early stages of mass market EVs. The thinking will evolve and your feedback will be recognized, you have contributed to future EVs from GM.

In automotive design and development it is not at all uncommon to have decisions market driven, feedback from focus groups, etc... the engineers likely did not want to display it that way, but based on the user experience, that was the decision.
 

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FWIW, I'm describing the bolt to coworkers as "The electric car you can forget is electric. It just drives like a regular car and it has a full tank every morning."
 

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I am still trying to wrap my head as to why they would include the line at the wrong place. Such an attitude to accuracy in the mechanical part of the car is unacceptable. Why is it acceptable here? I don't get it.
Actually, other cars have deliberately inaccurate instruments. The coolant temperature gauge in many ICE cars does not give a fluctuating reading as the coolant temperature fluctuates. Instead, it just puts the pointer at a temperature that is the nominal safely warmed up temperature when the actual temperature is within a wide range of normal temperatures. This can be noticed by reading the ECU's notion of coolant temperature with an OBD-II reader. For example, in an early 2000s VW, the pointer sits at 190F even when the OBD-II reader shows anything from 175F to 205F or so.

Speedometers in some cars intentionally read high, due to requirements in some countries where they must not read lower than the actual speed even when the largest possible tires that fit inside the fenders are installed. This can also be observed with an OBD-II reader or driving by the radar trailers that warn you what your speed is.

Distance to empty readings on ICE vehicles are also sometimes made so that the nominal 0 miles left really means that there is still some amount of fuel left.
 

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What I love about the CAFE standards is that they measure the sq footage under a car at the wheels and bigger cars are permitted to get less gas mileage.... so poof in the 1990's all the automakers started pushing design changes that moved the wheels to the corners of the cars, for better handling of course!
The "footprint" method of determine CAFE effect of a vehicle started in 2011.

However, having a large wheelbase and a small overhang outside of the wheels does help in getting the most interior room for a given size of car, so there were motivations to design vehicles like that even before the CAFE "footprint" method was used.
 

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I am now in the awkward position of writing a paper inspired by this screen issue. That paper has grown quite a bit -- eg, I just learned of a huge unintended consequence (the "MPG Paradox") of the CAFE standards whereas a company that makes more fuel efficient vehicles can have their CAFE penalty rise instead of fall as intended. It is because of a misguided use of MPG by NHTSA. This was the last straw for me and I have now changed my personal view on MPG vs. GPM. I used to think MPG was fine if used properly. But while MPG is not going away, and it does have its place, this CAFE error (among other things) has convinced me that GPM is far superior as the primary method of measurement.
CAFE is actually calculated by flipping MPG to GPM, taking the average, then flipping it back to MPG (harmonic mean).
https://en.wikipedia.org/wiki/Corporate_average_fuel_economy#Calculation
 

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There is an aspect of Hilltop Reserve which has nothing to do with battery degradation and which not been mentioned in this thread, although it has been in others. We are all developing “motor memory” (motor functioning of the human brain, not the auto) in the use of regen. This is either in left hand (regen paddle) or right foot (L mode driving) muscle motor memory. If I charge to full, I lose all regen, slowly regaining it over the first 5-10 miles I drive. This brain development may take 6 months to become fully subconscious. Pulling the regen paddle and getting NO braking means a quick trip to the brake pedal. IF I do not need > 200 miles on the first day after charging, using HTR allows “full regen capability” to be the norm. Taking range-challenging trips is less than 3 % of my driving, so I would prefer having normal regen be “my norm”, rather than the slow reaquisition of regen braking every day when I start my driving day.
 

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Someone tell the engineers we (at least I) want a battery conditioning option that lets you heat the HV battery while driving in subfreezing temperatures so the Bolt can peak fast charge upon arrival at a DCFC and not experience neutered fast charging rates due to a cold battery pack!
 

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Discussion Starter #16
surgeonFWW: That is an excellent point. It does come as a surprise to lose that regen when full charged.

boltage: You are correct...BUT the problem that I mentioned still remains. I will give you one simple example. This is more thoroughly discussed in my paper (copy on request).

Company makes 1000 cars getting 30 MPG.
CAFE target is 50 MPG
Penalty is 50(1000) (50-30) = 1,000,000 $.
Company now adds one car getting 70 MPG
You can stop now and work out the new fine! Here it is:

The fleet mileage is improved to 30.017 by this new car --- 1 / ( (1/1001) (1000/30 + 1/70)) = 30.017. The new penalty is now

50 1001 (50-30.017) which is 1,000,142.

Scary, no? That such an unintended consequence could result from people who, one thought, would have understood the goal of the policy. The problem would disappear if the penalty was just proportional to T - G for each car where T is the target GPM and G is the GPM for each car. Then each car counts "on its own". That is not the case in current MPG formula.

To be honest, this is the straw that broke the camel's back for me. I am a strong believer that the metric system has serious flaws (but don't want to start that debate here, and it is actually irrelevant to MPG vs GPM). And of course I am very familiar with MPG way of thinking. For the Bolt's rating of 4, mi/kWh is very convenient when computing range. But there are so many problems with MPG that I am belatedly coming around to the view that GPM is clearly the better system overall.

There is the MPG Illusion (in my paper)
There is the MPG Paradox (CAFE details above)
There is the MPG Singularity (this is the heart of GM's problem in the screen in question: they have not figured out how to handle the giant scale that arises).

And there is this new funny little aspect:

-mi/kWh and mi/(-kWh) mean the same thing. But we say it as "minus 5 miles per kWh". Typical responses to such a negative are: "what is a negative mile?"; "I will never drive 5 miles in reverse". This no doubt is why GM banished negatives from the screen. Tesla uses watt-hours/mile. Then the tradition of attaching the minus sign to the numerator causes no problem. -1000 means I get a kwH for descending one mile. I find this example fascinating!



bro1999: I can say that one of the engineers said that they do monitor forums such as this one


boltage: Yes, I know that instrumentation is not perfect. Still, a 2000% error (could be a 6000% error) is over-the-top. They did say they would look into the tire pressure issue (incorrect readings here at 9500 feet). As for speedometer: I know that traditional cars overestimate one's speed (and also one's distance I think). Has anyone checked the Bolt against, say, a phone app (not so accurate) or GPS watch (more accurate in my opinion) or other standard to learn whether the speed and distance are accurate?
 

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I have frequently compared my speed as reported by my Bolt speedometer and that speed independently reported by my Garmin SmartDrive GPS. They usually agree exactly but never differ by more than 1 mph. I have compared at speeds as low as 25 and as high as 75.
 

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I note that 40% degradation over 100000 miles does seem excessive. But will that actually happen? I had a 2005 Prius with 110000 miles when sold and a 2013 Plug-in Prius with 56000 when traded-in for Bolt. I cannot measure the degradation in those batteries, but there was no detectable degradation.
My Fusion Hybrid has 210,000 miles with no detectable degradation.

There is one possible downside to using hilltop reserve all the time. You might forget to change the setting when you do need 200+ miles the next day.

I'm on the side of just charging to full every night, just in case. I'm glad the engineers finally confirmed that this is a reasonable thing to do.
 

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There is an aspect of Hilltop Reserve which has nothing to do with battery degradation and which not been mentioned in this thread, although it has been in others. We are all developing “motor memory” (motor functioning of the human brain, not the auto) in the use of regen. This is either in left hand (regen paddle) or right foot (L mode driving) muscle motor memory. If I charge to full, I lose all regen, slowly regaining it over the first 5-10 miles I drive. This brain development may take 6 months to become fully subconscious. Pulling the regen paddle and getting NO braking means a quick trip to the brake pedal. IF I do not need > 200 miles on the first day after charging, using HTR allows “full regen capability” to be the norm. Taking range-challenging trips is less than 3 % of my driving, so I would prefer having normal regen be “my norm”, rather than the slow reaquisition of regen braking every day when I start my driving day.
+1

Thanks for mentioning that. It bugs me too.

I'm sure there is a good reason, but I don't see why the car can't slow down as if it is regen-ing, even when the battery is full.
 

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I'm sure there is a good reason, but I don't see why the car can't slow down as if it is regen-ing, even when the battery is full.
Power being generated by the motor has to go somewhere, and where it would otherwise go is into over-heating and over-charging the battery, both of which would limit its life.
You probably don't want a heat-sink the size of a dinner plate just to dissipate excess unused energy - easier to limit the amount of power re-genned.
 
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