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Guess O Meter Improvement

4898 Views 62 Replies 19 Participants Last post by  Crwddyz
I suggest the GOM be converted to % battery charge instead of estimated miles left. We would still have maximum and minimum mile estimates. That gets us away from always saying the GOM is wrong. This would also keep me from trying to count bars with my eyes off the road. Haha
At least make it an option to see % charge instead of miles. In my opinion % charge is more meaningful than a mileage estimate which is always wrong due to so many variables. Hopefully GM will read this. Doubtful I know.
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I think the GOM should also consider the regen... because I'm pretty sure it doesn't.

Easy example: A 16 mile 75 mph drive nets me ~4 miles/kwh. Part of its downhill... GOM seemingly only considers the constant 75 mph energy expenditures rather than the possible regen. It's usually off by 10-20 miles in its estimate. While I drive a total of about 32 miles a day, going by initial GOM vs final GOM estimate, GOM says I drive like 10-15 miles total in a day.

The infotainment and myChevy app/website are a mess. The infotainment energy efficiency considers the regen, but website does not. MyChevy website shows my efficiency at 3.2 miles/kwh ... and that actually makes sense since 75 mph driving for 20-30 minutes is energy-intensive!
Incorrect. The gom is just a rolling fuel economy type calculation same as used in an ice only for kwh instead of litres. It uses the vehicles past efficiency to guess future range. The vehicles efficiency calculations include regen.
No, it's not. You're incorrect. The DIC is the actual rolling fuel economy type of calculation and it disagrees with the GOM.

There's just no way 80% SOC corresponds to a 160 mile GOM prediction when DIC/Infotainment reports 4 miles/kwh. And I'm not the only one to report these discrepancies. Have a look at the 2017/2020 tables in this article:

If GOM was really looking at regen, I shouldn't have 10-20 mile prediction errors and I should get predictions like this:
4*0.8*64=204 miles

4 is what DIC and Infotainment show

If I use 3.2:
3.2*0.8*64 = 164 miles (this is almost EXACTLY what I see on GOM).

3.2 is what myChevy shows. This is probably my miles/kwh WITHOUT regen.
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Wrong. The gom is also a rolling fuel calc. It's uses approximately the last 50km of driving history. You can see this 50km in graph form one one of screens of the touch screen. It is broken down into segments. I have watched the gom spike as inefficient segments at one end drop and are replaced by more efficient segments at the other end. I have watched the gom correct itself to my 20% reduced speed after 25-30km to make a detour.

The dic reports from when it was reset last. When's the last time you reset it?? Likely more than 50km ago so obviously they won't agree. You see those changes as your efficiency changes throughout the day.
Wrong, the GOM is not a rolling fuel calculation. Did you look at the WIND-WORKS article? You're objectively wrong and those numerous measurements show significant disagreement. Your anecdote does not contradict tables of numerous GOM and efficiency values (they do not agree, even when the car is brand new with basically no usage). Whatever GOM does, it's not a simple rolling fuel calculation like you think it is.

Not that it really matters, I've reset the DIC numerous times to test this. And I've done numerous tests to quantify battery capacity using kwhConsumed/diffSOC% to make sure my battery is actually around 66 kwh.

Why doesn't this DIC thing really matter? Because the Infotainment system will report miles driven and kwh hours consumed. You can simply divide the two quantities to get miles/kwh... no issue right? And these values reset when you recharge. That's definitely going to give you an accurate efficiency within - what you claim - the 50km history (my 32 mile total commute ~ 51 km). But they don't agree still! Oh, but how can that be?

NOTE: You make the bold assumption that the Infotainment's energy statistics is used by the GOM (it is almost certainly not used by the GOM).

Now, have you ever noticed that the Infotainment system will count backwards kwh consumed during regen? This directly affects your manual efficiency calculation from the Infotainment system... without kwh consumed counting backwards like that, my efficiency calculation would be far worse.

And that leads to my hypothesis: The GOM pessimistically measures only expenditures of energy and not regen to produce its range predictions.

If the Infotainment can count kwh consumed backwards during regen, then perhaps if it didn't, the measured efficiency would be in line with GOM's characteristically lower range predictions. It's a very simple explanation! On top of that, we all know the myChevy website/app would produce seemingly non-sense efficiency values (usually much lower). But these values (at least in my case), agrees almost exactly with the GOM. And they agree with my 75 mph commute (which SHOULD NOT be 4 miles/kwh).

And a nicety of this hypothesis (if true) is that it means the GOM is giving you driving range estimate assuming you never regen. This is the most conservative estimate you could possibly want, right? The GOM might be telling, "You can drive N miles if you never regen." And that makes a lot of sense to me.

Does my hypothesis explain your observation?
I have watched the gom correct itself to my 20% reduced speed after 25-30km to make a detour.
In fact it does! If you're reducing your speed, your energy consumption goes down. If the GOM only operates on energy expenditure to makes it prediction and you happen to be using less energy because you're driving slower, then that means GOM should provide higher range predictions.

And it explains my situation very well too! My commute is partly downhill. I drive 75mph for 20-30 minutes every day and I manage 4 miles/kwh through manual calculation from Infotainment (since you don't want to trust my DIC). How do I manage that? I am regenerating energy going downhill and my Infotainment system is counting backwards kwh consumed.
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It does. I watch the GOM estimate go up and down as I'm driving up to mountain passes and back down to valleys here in British Columbia. On long downhill stretches you can see the "Energy Used since last full charge" number counting down at the same time that the GOM trend bar is pegged at the very top and the estimated, min and max ranges are all ticking up by a km or two for every km traveled.
My estimates have never gone up.

I have, however, arrived at work with nearly the same estimate as when I departed from home... 16 miles before.
I'm going to agree to disagree with the conclusions drawn in most of that and let others continue to share their agreement the gom is a rolling fuel economy calc that does include regen (it's literally shown on the efficiency graph and the trend bar). I have no idea what articles you're referring to (quick search on Google found nothing relevant) and there is a lot irrelevant stuff and other weird assumptions in your post but I don't think breaking it down will make any difference.
The most egregious counterexample to your claim of a simple rolling average:
Odometer: 376 miles (brand new car)
GOM-Mid: 265 miles
Efficiency: 5 miles/kwh

And there are several examples like that.

I think that you are missing the point @enslay
The GOM is doing its own calculations based on a set of parameters while the DIC is only displaying distance travelled, energy used and energy produced like an odometer and fuel gauge.
The GOM appears to be using an amount of distance that from what I see to be about 40Km and guesses how many Km you have left. AKA a rolling calculator while the DIC is just the facts at the time you look at it.
don’t try to compare the 2, they are not reporting the same thing.
I avoided using the DIC in my argument.

I relied on Infotainment's reported miles drive and kwh consumed (which always reset on recharge). In fact, it's the Infotainment counting backwards kwh consumed on regen that led to my hypothesis about GOM only measuring spent energy (and never regen). It perfectly explains myChevy's weird efficiency, 4 miles/kwh 75 mph daily driving, and the enormous discrepancy between my reported efficiency and GOM's estimate.

EDIT: Need to emphasize that 75 mph!
I don’t understand how the GOM could reasonably work without including regen and only counting energy spent. It would CONSISTENTLY show range well below the EPA rating, which includes regen.
Well, I'm open to ideas on how to explain my daily 32 mile commute with 4 miles/kwh (manual calculation from miles drive/kwh consumed)... yet I have ~160 miles GOM with 80% SOC (should be ~200 miles at my efficiency).

The deciding factor for GOM is that I drive 75 mph. It does not seem to care that I mildly go downhill a bit and regen enough energy to scrape 4 miles/kwh.
Alright folks... here you go!

The GOM does not use your Infotainment measurements or DIC.

Here's 80% SOC... just finished charging

Here's the efficiency plot for the last 50 miles (which is larger than 50km... I guess they just use 50 [some measurement unit])

And so that you know I'm being honest

Now I haven't measured my battery capacity in a few months with kwhConsumed/diffSOC%... but last time I measured it, it was around 63-64 kwh max capacity.

So there you go. Today, 12/2/2021, 64 degrees F (17.8 degrees C), GOM says 151 miles and Infotainment says more-or-less 4 miles/kwh in the last 50 miles.

The GOM does not agree with or use your measurements from DIC or Infotainment.

I'm open to ideas for an explanation. But the GOM is clearly not some simple rolling average. It does care about your speed, and I drive 75 mph most of the time driving (mostly commuting on the highway).
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You haven't been trying hard enough:
I somehow get 4 miles/kwh with a 75 mph daily drive. That's pretty darn good!
You haven't been trying hard enough:
View attachment 39068
This was going eastbound down the grade at Copper Mountain on the Hope-Princeton highway. As you can see I gained 10 km of estimated range in less than 3km of actual traveled distance. I await your explanation of how that could have happened without regen having been taken into account.

Note that the average efficiency number of ~21 kWh/100 km is high (i.e., not very efficient) because I had to climb up the pass to get to the top of the mountain, and also that I had not reset the trip odometer / efficiency display after having charged at Manning Park.
21 kWh/100 km means you get about 2.95 miles per kwh. If you're a 2017-2019, you should have about 203 km on your GOM at 75% (you approximately do).

Your DIC is in good agreement with your GOM. At 80% with 4 miles/kwh, mine should read 205 miles... it reads 151 miles.

You should show the Infotainment's miles driven and kwh consumed (it's conveniently summarized on the home screen). That's more trustworthy than the DIC.
For the life of me, I couldn't find the energy efficiency tool on anymore. But I just got the December diagnostics e-mail

Now check this out!

This is Chevrolet telling me that 35 kWh /100 miles is my efficiency!

So ... 35 kWh / 100 miles is about 2.86 miles per kwh

2.86*0.8*64 = 146 miles

So there you go! Good agreement with my 151 miles reading earlier. GOM is using whatever Chevrolet collects... which is quite different than what DIC and Infotainment measure.

I mean, clearly regen is doing something for @Sean Nelson. Although averaging max(0, energyConsumed) where energyConsumed < 0 is regen would have a similar effect as he posted. That's the only explanation I can think of anyway... I only get 4 miles/kwh through regen and if I didn't benefit from regen, I'd probably have 2.86 miles/kwh like Chevy reports (75 mph = 121 km/h eats up a TON of energy).
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I hope you understand that the efficiency number is averaged only over the distance since you last reset it and is strictly a measure of energy used vs miles driven.
C'mon man... how many times do I have to say this... I hope you understand how to compute efficiency manually.

Why doesn't this DIC thing really matter? Because the Infotainment system will report miles driven and kwh hours consumed. You can simply divide the two quantities to get miles/kwh... no issue right? And these values reset when you recharge.
I will further add that the energy reported in the Infotainment includes factors like HVAC. I'm sure you've seen the "Climate" breakdown of energy consumption. The manual efficiency calculation will capture those factors implicitly.

Meanwhile the range estimate is a much more speculative algorithm that attempts to predict the future by drawing on many factors including temperature, HVAC consumption, efficiency during previous driving cycles, etc. - and it's heavily biased by the very recent past.
I showed you the recent past (50 miles history). Explain the discrepancy... is it heavily biased by my consistent 4 miles/kwh efficiency in the last 50 miles (achievable only via regen!), or is it heavily biased by my 75 mph speed? I think this is obvious.

"Ironclad agreement" is an understatement. We're talking about a 50 mile range discrepancy. We're talking about a difference of 4 miles/kwh (manual calculation, Infotainment) vs 2.86 miles/kwh (Chevrolet).

But yes, the range estimate does take regen into account.
If it actually takes regen into account, explain the discrepancy in my numbers! Explain Chevrolet's numbers.

On the other hand, it could behave the same for you if it didn't take regen into account... because it could do something like this:
Although averaging max(0, energyConsumed) where energyConsumed < 0 is regen would have a similar effect as he posted.
Yeah, I don't know. All I know is Chevrolet's number is 2.86 miles/kwh and it aligns well with the GOM prediction. And I know that there's no way I could have 4 miles/kwh driving 75 mph for 20-30 minutes. Impossible without regen.

So of course you won't see ironclad agreement between past efficiency and predicted range - that's only to be expected since they're based on different data and are serving different purposes.
It's measuring the same data, and possibly using the same sensors and possibly augmenting it with other extra measurements (e.g. outside temperature). GOM is doing something DIFFERENT with that data.

I hope I've successfully empirically demonstrated that the GOM is NOT some simplistic rolling fuel calculation like found in DIC and Infotainment. It's a more sophisticated, in your words, speculative algorithm.

EDIT: Maybe the GOM is a Kalman filter

In a very strange way, it would be a kind of rolling average calculation. Just not with scalar values and weights.

I'll have to think if such a hypothetical Kalman filter can have consistent behavior between both of our observations.
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Thanks again, I’ll go for a drive today look for that trend bar. To verify when you say menu on left are you referring to the menu options on the steering wheel?
Don't worry. It's a subtle feature that's hard to notice. I didn't notice it for a while either.

Have a look at this picture:

On the very left of the 151, there's a gray arc. See it? The arc extends from the 178 max range down toward the 123 min range.

When trending above average, a green line will fill the gray arc starting at 151 and rising along the arc toward the top of the image (toward 178).
When trending below average, a yellow line will fill the gray arc starting at 151 and falling along the arc toward the bottom of the image (toward 123).

EDIT: I will add that the length of the line varies by how much you trend above/below. So if you're trending "a lot", the line could very well touch the 178 or 123 marks. If you're trending "a little", might be a small line far from touching 178 or 123 marks.

You can also see it from @Sean Nelson 's post (his is trending upward "a lot").
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I'm not going to get into debates about past efficiency vs. estimated range because they are apples and oranges and I see no point in it.
No, it's because you can't explain it. You "see no point" because you don't know. There's the numbers from myself and WIND-WORKS and your observations pooled.

EDIT: Just so you know, there's nothing wrong with not knowing.

If you feel your numbers are cause for concern then I guess your best course of action is to talk to your dealer about it. Good luck with that.
If you participated in the thread, the consensus from other posters was that the GOM is some kind of "fuel economy type of calculation" (EDIT: As in some kind of simple rolling average). I have completely thoroughly debunked that misconception... again (this is not the first time).

I never indicated any cause of concern for my numbers anywhere in this thread.
My 2020 Bolt does have a similar discrepancy that @enslay sees between DIC average mi/kWh and GOM range: 4.1 mi/kWh but only ~170 miles at 80% (actual 77%).

I'd been attributing it to the GOM not knowing the correct battery capacity. I think Sean Graham has mentioned somewhere that you need to discharge to below 40% for at least 4 times before it will figure out the capacity and I have never discharged that low. (Also, I've only charged up to 100% once.)

A few months ago, the GOM actually started displaying more reasonable numbers: ~210 miles at 80%. This was soon after I had discharged to the lowest I'd ever gone (~45%) so I thought maybe it had figured out the correct capacity. However, it reverted to the low GOM numbers after a couple of charging sessions so I don't really understand what's going on.
Maybe. I'll have to try discharging it below 40% once I get the new software (who knows when!). I charge it everyday in accordance to the recall... which vaguely recommends "charging more frequently" or something like that.

I attribute the GOM's estimate to daily driving at 75 mph. And the Chevrolet monthly diagnostics e-mail provides an efficiency value that matches the GOM's predictions. The DIC or even manual efficiency calculation shows around 4 mi/kwh. And that's surely due to regen and going downhill.... There's just no way I could manage that at daily 20-30 minutes continuous 75 mph driving.
I am not sure what part of the sentence you can’t understant: the GOM value is based on the value "of the efficiency" before the last reset. This value is based on the 3 T (temps, terrain and technique) including regeneration and everything you think it might not be taken in consideration.
No it's clearly not.

You wrote that I am very efficient at driving and you're somehow telling me that I drive at "maybe 50-55 mph" and yet the GOM spits out range values of 151 (for example)... it's usually more like ~160. It's not like a one-off thing. This is every day for months! OK? Do I need to start a blog and upload pictures everyday or something?

Do you know why the GOM likely spits out range values like 151? Because I drive 75 mph for about 20-30 minutes (one way) every weekday for the past 6 months. Some of its downhill, I get some regen when I get off the highway. But ultimately, most of my commute is at 75 mph.

Showing the last 50 km efficiency numbers and intentionally hiding the real m/kWh on board (by showing the tire pressure info screen) registered since the moment you reset last time the m/kWh is useless and you don't prove anything but the fact that for the last 50 km you drove very efficient, maybe 50-55 mph. Nowhere in the screens you show is 75 mph indicated.
What, do you want me post a new picture of essentially the same numbers, every single day for months on end? No, it's 75 mph on about a 10 mile stretch of interstate highway. My gosh, why would I lie about my commute?

Here's what I generally look at in the morning when I arrive at work and later in the evening when I arrive home. It's very hard to make a mistake from this... and I roughly see this (more-or-less) every single day! Here's an example of yesterday when I arrived at work:

And this resets on recharging. It's hard to be mistaken from manual calculation from these numbers (just divide them). Criticize the efficiency screen or DIC all you want... this is consistently about what I see in the morning and evening and there is no possibility of factors like the DIC not being reset or something like that since this just simply reports miles driven and kwh consumed (since last full charge and I charge every night).

I have my Bolt EV for long enough to know very well that it’s GOM is one of the best on the market. It never failed to "predict" very accurate and it’s simple for me to calculate what I need to do to go where I want:
For exemple, if I need to go 300 km and I have a previous consumption of 23 kWh/100 km… this tells me I will need to stop charging for 15 minutes at around 250 km mark if I keep the same 23 kWh/100 km or that I should slow down the speed to get about 19 kWh/100 km and not charge at all before destination. That’s why I love the MyChevrolet app because it tells me exactly the SOC of my battery.
"It works for me, so it must be perfect for everyone else"

I am relatively sure it's working correctly for me because I drive daily at 75 mph for prolonged periods of time (i.e. inefficient). That's why I get figures like 151 miles for range estimates at 80% SOC - and inspite of regen scraping back some on some of that inefficiency. And the myChevrolet efficiency numbers seem to convey the same thing (and surprisingly on the dot with GOM!)... for example last month, I get 2.86 miles/kwh (35 kWh/100 miles). But you see that screenshot above? I still see numbers like that everyday. That's all regen and some downhill driving.

EDIT: For those sticklers out there... I went cross checked with Google Maps. While the entire commute is 20-30 minutes, about 11.7 miles is highway driving of the 16 or so mile commute. The time spent at 75 is about 10 minutes.
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So for the sticklers, you do in fact 9 mins at 75 mph (get out of the way the 38 seconds for acceleration/deceleration) and the other 10-20 mins you do it in stop and go traffic. The Bolt EV is doing about 3.3-3.4 m/kWh at 75 mph and in the stop and go the number can very well rise up to what you see, around 3.7 m/kWh (16.7/4.5 shown in the above picture).
Now, the problem you have is that you see 151 miles on your GOM at 80% of SOC right ? With 178 miles best and 123 miles at worst. I don’t see a problem at all !
Based on your pictures above, you would see 188 miles at 100% in average and 222 miles at best at same 100% SOC on your GOM.
Your average consumption is 3.7 m/kWh, then at 100% SOC with 57 kWh available battery (could be lower) it means : 210 miles. I really don’t see any problem having a 10% difference between the values you see and the ones calculated. All you do is nitpicking just to prove something you fail to prove.
So just for reference, this is 2021 Bolt. So here's the problem... I'm closer to 4 overall, but we'll stick to 3.7

The GOM should predict something like this (if it's really based on efficiency alone)
3.7*0.8*64 = 189

Or if you want to be a stickler, it's probably more like
3.7*0.78*64 = 184

I'm getting values like 151 or 160... consistently. You can see several examples of similar anomalous numbers on that WIND-WORKS article I linked.

NOTE: ~64 is what I get when use WIND-WORKS methodology to estimate max battery capacity... run down the battery and calculate: kwhConsumed/diffSOC%. In fact, it's the low ball GOM ranges that led me to the WIND-WORKS site to begin with (and to finally conclude that GOM is not actually doing something simple like DIC or Infotainment). I also got OBDFusion and looked at the relevant PIDs and the battery looks completely fine.

The myChevrolet site (used to be accessible) and the monthly diagnostic e-mail (came a couple days ago) show an efficiency of 35 kWh/100 miles (2.86 miles/kwh).

This is actually pretty accurate compared to the GOM:
2.86*0.8*64 = 146

I think the GOM and myChevrolet are doing something different with the efficiency values. Maybe it's suppressing outliers by considering, say, median or some percentile efficiency over all the drives. Or heck it could be something more sophisticated like a Kalman filter (still thinking about this). Because I really do think 2.86 is realistic considering ~75 mph and the GOM is rightfully low balling the prediction since 11 miles out of 16 is low efficiency driving.
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