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The Bolt's estimated range is shown by the numbers on the lefthand-side display of the dash, often referred to by longtime Bolt fans as the GOM, or Guess-O-Meter. The car uses your recent driving to guess how far you might be able to drive given your recent driving efficiency.
  • If your efficiency is about 4 miles/kWh, the 100%-charge range will be 238 miles for a 2017–2019 Bolt, and 259 miles for a 2020 Bolt.
  • If your efficiency is about 3 miles/kWh, the 100%-charge range will be 178 miles for a 2017–2019 Bolt, and 194 miles for a 2020 Bolt
  • If your efficiency is about 5 miles/kWh, the 100%-charge range will be 298 miles for a 2017–2019 Bolt, and 324 miles for a 2020 Bolt
The same is true for any car. A gasoline car (which these days can often show estimated range as well) can drive further on a full tank when driven efficiently compared to driving it inefficiently.

New Bolt owners often take some time adjusting to the estimated range being displayed so prominently and the guesses about the range varying over time. There are often threads like “I used to be able to charge my care to 238 miles and now it only can charge to 178 miles! Is there a problem with my battery?!?” (due to efficiency dropping). Strangely, perhaps, few people post about the opposite, where the range increases due to efficient driving. In contrast, gasoline cars don't tend to display their range so prominently, and probably most owners wouldn't think their gas-tank had suddenly shrunk if the estimated range dropped after hard driving.

A while ago, I wrote a parody thread (where I pretended I was super concerned that my range kept going up), and a few people worried that someone might see that thread and not realize it was utterly absurd. (They recommended all absurd humor be banned from the forum!) So, in the interest in drawing eyes to the right thread, I've given this a good title to attract those newbies who think they have issues and curious onlookers, but kept it serious and informative.

Now let me share a bit of real data showing GOM fluctuations.

I went for a little expedition, leaving home and heading up mountain roads, ten miles at an average of 6% grade (some parts much more than 6%, some less). I left with 87% charge (“hill-top reserve”), and arrived with the green battery state-of-charge bars showing less than 75%. The car went from thinking it had 241 miles at 87% charge (GOM thus expecting 4.8 miles/kWh efficiency) to reading 161 miles at an estimated 74% charge (GOM thus expecting 3.75 miles/kWh efficiency). So I drove 10 miles but appeared to “use up” 80 miles of range. Of course, in reality I'd just made the car more pessimistic about life by driving it hard. When I was done on the mountain, I drove back down again. Returning home, regenerative braking had taken the battery back to 79% and the GOM was back to reading 218 miles. Adding in the 20 miles I'd driven, I was at 238 miles of range from a hill-top reserve charge, which I always like, but still less than what the car had been thinking when I set out.

I hope this story shows how much the GOM can fluctuate, even with just ten miles of driving. The guesses are based both on recent driving and some significant amount of history. If it was based just on very recent driving, the drop in estimated range from driving up a 6% grade would be even worse.

One other thing, driving up the mountain at 50 mph, I came up behind someone who as going at a reasonable speed, but just enough slower for me to catch up. As I got to them, there was a short two lane section and they pulled to the side to let me past (staying at the same speed). To avoid making them slow down because the two lane part would end very soon, I powered past them. The Bolt accelerated smoothly and easily, even though this was one of the steepest parts of the climb. I love this car (although perhaps it almost takes some of the fun out of mountain roads since it is utterly relaxed the entire time).
 

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Yeah, mountain driving is challenging if you're expecting to drive to the limit of your range, because the range estimate is optimistic before you go up, pessimistic at the top, and optimistic when you get back down to the bottom again. So it's hard to judge your progress by comparing the range estimate to your GPS's "miles to go" display like you can on flat land. It's here where the "trend bar" that stretches up or down just left of the state of charge bars is really useful, because it reacts to new driving conditions a lot faster than the range estimate. And it also helps to have a good feeling for your miles/kWh (in terms of bars on the range display) under various driving conditions.
 

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Speaking of a little humor, I was bragging to a friend who just got a Kona electric that I was getting about 8 miles/kWh. He challenged me about and I showed him the read-out on screen. He was astounded. Then I explained that I had reset it right before coming there and drove down hill all the way. hee hee...
 

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Cool post! Thanks.

It must not be linear. I get an average of 4 miles/kwh and my 87% charge range is ~207 miles in my new 2021 Bolt. About 2-3 weeks ago, it used to predict ~225 at 87%. And when I bought it a month ago, it was ~259 at full charge. My current 87% range seems low but I guess it's the GOM. I will play with OBD2 to see if a cell went bad or something... but I'm guessing it's not linear (i.e. it's not simply 259*0.87 for SOC and rated milage nor is it simply 4*65*0.87 for average miles/kwh, 65kwh battery and SOC, etc...).

However, I do a lot of 70+ mph highway driving. My 4 miles/kwh comes from going downhill to work one way and uphill the other... all the while going 70+ mph mostly both ways. It somehow averages out to 4 miles/kwh though!
 

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Cool post! Thanks.

It must not be linear. I get an average of 4 miles/kwh and my 87% charge range is ~207 miles in my new 2021 Bolt. About 2-3 weeks ago, it used to predict ~225 at 87%. And when I bought it a month ago, it was ~259 at full charge. My current 87% range seems low but I guess it's the GOM. I will play with OBD2 to see if a cell went bad or something... but I'm guessing it's not linear (i.e. it's not simply 259*0.87 for SOC and rated milage nor is it simply 4*65*0.87 for average miles/kwh, 65kwh battery and SOC, etc...).

However, I do a lot of 70+ mph highway driving. My 4 miles/kwh comes from going downhill to work one way and uphill the other... all the while going 70+ mph mostly both ways. It somehow averages out to 4 miles/kwh though!
That makes me wonder if speed is weighted more heavily than terrain in the GOM algorithm. It may not be a direct calculation based on overall miles / kWh efficiency.

Also, is your auto-defog setting turned on or off? As the weather gets warmer or more humid, auto defog may run more and impact your GOM. I've noticed that simply turning on the A/C or heater will immediately affect my GOM, regardless of my miles / kWh efficiency at the time.
 

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Speaking of a little humor, I was bragging to a friend who just got a Kona electric that I was getting about 8 miles/kWh. He challenged me about and I showed him the read-out on screen. He was astounded. Then I explained that I had reset it right before coming there and drove down hill all the way. hee hee...
The 5 mile trek I do fairly regularly to my local Home Depot\Walmart and a few restaurants we regularly order from is downhill much of the way. It is not uncommon for me to arrive with 51.1 (the max the Bolt will calculate on the trip meter) mi/kWh efficiency. The return trip, of course, is uphill and the round trip 10 miles is generally up to 6 mi/kWh in summer, 4.5 winter.
 

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Can be make this a Global, Bookmark, FAQ, or automatically direct all new users to this post?
I can sticky this one, it certainly should get the message across. But it should probably go on the Introductions thread, that is where new owners will often start. @Vertiformed, you OK with me moving it and sticky it?
 

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It means you have ~59.5 kWh usable, like lots of others with the "66 kWh" pack.

Ask @Telek what is going on with these packs.
Lots of others? I can't seem to find any examples of others with this issue. Can you link some examples?

EDIT: This is interesting, but it's not 59.5 kwh which is quite a bit less than advertised for a 2021.

I will try the simple math proposed in that article using the infotainment's measure of spent kwh and difference in percentage from MyChevrolet app.
 

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Discussion Starter · #11 ·
I can sticky this one, it certainly should get the message across. But it should probably go on the Introductions thread, that is where new owners will often start. @Vertiformed, you OK with me moving it and sticky it?
I don't object, but I think we'd be better off with an explicit and obvious FAQ.

The Bolt subreddit has one although interestingly, it doesn't seem like it needs to answer this question. (Could it be that somehow reddit users are less likely to think that a battery is full of miles?)
 

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Lots of others? I can't seem to find any examples of others with this issue. Can you link some examples?

EDIT: This is interesting, but it's not 59.5 kwh which is quite a bit less than advertised for a 2021.

I will try the simple math proposed in that article using the infotainment's measure of spent kwh and difference in percentage from MyChevrolet app.
From my reading of folk's posts, it appears that either the "66 kWh" packs are not 10% more capacity than the 2017-2018 packs, or the algorithms GM is using to estimate Ah, kWh, and GOM are screwed up.

I suggest you load Torque Pro, and @Telek 's PIDs, if you are concerned.



[edit] Or worse, GM's battery problems are not limited to Korean, old chemistry packs.
 

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From my reading of folk's posts, it appears that either the "66 kWh" packs are not 10% more capacity than the 2017-2018 packs, or the algorithms GM is using to estimate Ah, kWh, and GOM are screwed up.
I just noticed another example of what I see. Have a closer look at the WIND-WORKS link. Take a look at the GOM table for the 2020 Bolt.

You can see deviating estimates for lower miles/kwh values. For example:

GOM estimates that with
3.3 miles/kwh, the author has the range: low=217, mid=265, high=312
3.6 miles/kwh: low=192, mid=244, high=284
3.7 miles/kwh: low=227, mid=277, high=326

The GOM doesn't seem to be doing the simple linear calculation with our displayed average. It's doing something more complicated...
 

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One thing about hilly, curvy driving on unfamiliar roads is that we tend to drive somewhat under the posted speed limit. Last Tuesday we drove "up" to the New River Gorge National Park for some day-hiking. We were at full charge at departure. (Yes, I have had the "final fix".) On arrival back home, we had driven 200 miles but still had 45 miles left on the range estimator. We have a 50 month-old 2017Bolt EV/battery. While not being an "exact" measurement of battery degradation, a 245 mile range certainly does not indicate very much degradation. If I trade-in this Winter, it will be only for adaptive cruise control, lane centering (vs lane departure warning with very poor lane keep assist) and a much higher (>175 vs 55) max DCFC rate.
 

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I just noticed another example of what I see. Have a closer look at the WIND-WORKS link. Take a look at the GOM table for the 2020 Bolt.

You can see deviating estimates for lower miles/kwh values. For example:

GOM estimates that with
3.3 miles/kwh, the author has the range: low=217, mid=265, high=312
3.6 miles/kwh: low=192, mid=244, high=284
3.7 miles/kwh: low=227, mid=277, high=326

The GOM doesn't seem to be doing the simple linear calculation with our displayed average. It's doing something more complicated...
I have a ‘20, and I am not seeing the same GOM estimates as that graph at all.

I just bought this ‘20 and had a ‘17 previously. The GOM is different between both, but both go towards the conservative side with the ‘20 super conservative.

I have only charged to full 3 times. The GOM prediction is 240, and my cumulative average is 4.1 miles per kWh. The furthest I have traveled during one of these full charges was 187 miles, and the car showed 31% remaining charge on the MyChevrolet app. I didn’t note the kWh used for that excursion, but the average was 4.1, so probably 45.6 kWh used, leaving me ~20.

With that data, I should be able to go another 82 miles on the 31%, for a projected 269 miles total for the battery pack @ 4.1mi/kWh.

The GOM occasionally adds a few miles within a few miles of initial driving.

All things considered, I would rather the GOM challenge me to beat it’s prediction than lull me into thinking I can up the speed.

Why mine or some 20-21’s read differently from others would probably need to be answered by “the ghost in the machine”.
 

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but both go towards the conservative side with the ‘20 super conservative.
Seems like there's a bit of a curve near the end to me. Like it will say I've got 10 miles more range than needed and I'll maintain my pace, watching it maintain a roughly 10 mile buffer for a long ways but as I get close to 40 miles or so left the range meter starts to slow down and I'll have 20 miles or so at the destination.
 

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I have a ‘20, and I am not seeing the same GOM estimates as that graph at all.

I just bought this ‘20 and had a ‘17 previously. The GOM is different between both, but both go towards the conservative side with the ‘20 super conservative.

I have only charged to full 3 times. The GOM prediction is 240, and my cumulative average is 4.1 miles per kWh. The furthest I have traveled during one of these full charges was 187 miles, and the car showed 31% remaining charge on the MyChevrolet app. I didn’t note the kWh used for that excursion, but the average was 4.1, so probably 45.6 kWh used, leaving me ~20.

With that data, I should be able to go another 82 miles on the 31%, for a projected 269 miles total for the battery pack @ 4.1mi/kWh.

The GOM occasionally adds a few miles within a few miles of initial driving.

All things considered, I would rather the GOM challenge me to beat it’s prediction than lull me into thinking I can up the speed.

Why mine or some 20-21’s read differently from others would probably need to be answered by “the ghost in the machine”.
If I had to guess, it's integrating something against the Efficiency(Distance) function to calculate its ranges. I haven't had a chance to play with the values in that efficiency vs distance graph yet (found somewhere in Energy menu in Infotainment system)!
 

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I must add to this, that the GOM is essentially useless as a static measure. However, as a dynamic measure used in conjunction with the trend bars, I find it to be quite accurate.

While I have never been able to drive in a manner that the trend bars never extended above or below the GOM, I have been able to come close to averaging that on level roads by adjusting my driving technique. In these cases I have been able to drive exactly the distance the GOM said I could.

The GOM should never be discussed as a static measure. It should only be discussed in conjunction with the trend bars. The trend bars indicate how the vehicle is currently being operated with respect to the GOM.

Ed
 

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The GOM should never be discussed as a static measure. It should only be discussed in conjunction with the trend bars. The trend bars indicate how the vehicle is currently being operated with respect to the GOM.

Ed
I still think the GOM is an evil plot to ostracize OCD drivers to quicksale the thing before it “gets you” (!!!). I have noticed an occasional bolt owner over the years that couldn’t deal.
 

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I will do some napkin math like the WIND-WORKS article to estimate my battery capacity (I've seen a youtuber do this too for calculating battery degradation). In the future, I will try OBD Fusion (no Android for me).

I am guessing that one needs to discharge 16 percentage points or more of battery to get a relatively accurate battery capacity measurement with the napkin math. This value can be found by analyzing the overall behavior of the round off error in the displayed SOC on MyChevrolet (the same can be done for kwh spent value, but if you spend 16%+ of your battery, this value is of less concern!).
 
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