[Vertiformed]

If you've just become a new owner, congratulations!

There are some questions (and misconceptions) that seem to come up over and over. In general, before asking about something, it doesn't hurt to search the forum (or check out the other Bolt FAQs that exist, such as this one on reddit.)

One recurring new-owner concern relates to the (mistaken) idea that the battery contains “miles” and that when fully charged, the readout should say 238 miles for a 2017–2019 Bolt, and 259 miles for a 2020 Bolt because that's what Chevy lists as the full-charge range.

Digging a bit deeper:

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 (and I mean recent as in a weighted average based the last 50 miles or so, and certainly not the last 4451.9 miles displayed by the car in the picture above).

• If your recent 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 recent 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 recent 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 car 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, there are fewer occasions where 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.

I think part of what causes confusion is that the miles number draws people's eyes, and they think it represents the battery's state of charge. But if you want to know how much charge is in the battery, that is not what you should be looking at.

Note that this display is only accurate to the nearest 5% and rounds up, so seeing all 20 bars means your state of charge is somewhere between 95.1% and 100%. Only when you drop down to ≤ 95% will the top bar disappear.

Charging to 100% Limits Regen

If you charge your Bolt to 100%, regenerative braking is limited.

In this example, the car is only going to allow about 20 kW of regenerative braking (light braking) rather than the full 70 kW.

The easiest way to avoid limited regen is to set the car to only charge to about 90% full. In early Bolts, this is the “hill-top reserve” feature, which is fixed at about 88%, and in later Bolts you can choose a percentage. Not charging to full is slightly better for the battery, too, but the jury is out as to whether the benefits will ever be detectable for most owners.

People are often confused about this because the car decides how much to limit regen, and various factors enter into the decision. For example, it can also limit regen when the battery is very cold or hot. But if you charge to 100% and let the car sit a while, the battery will have settled a bit and the car will be more generous in what it allows. This leads to very different anecdotal accounts of how much regen is available when charged to full, some people say there is plenty, and others say there is almost none at all. The truth is it's situational, but the car's display tells you how it is.

Some people think that there couldn't be room for any regen at all 100% charge, but 10 seconds of regen at 20 kW is about 0.05 kWh, or adding less than 0.1% to the battery. Also, the “100%” point for the battery is arbitrary (a particular voltage to charge up to and not beyond). The car could in principle charge the battery to 110% or discharge it below 0%, it would just wear it out prematurely to do so. GM (and LG) picked the 100% and 0% points in a trade-off between battery life and battery capacity.

Conclusion

If you learn one thing from this post, it's that the battery doesn't contain miles (so the range display is not showing you battery capacity).

Actually, to be pedantic, the battery doesn't even contain kWh, although we usually like to pretend it does. It contains chemical potential energy that is converted to electrical current at a particular voltage, and the only real way to know how much usable energy it contains is to drive the car and see how much you got out. If you drive from 90% down to 23% and used 40 kWh, you've used about 2/3 of the battery's capacity (90% - 23% = 67%) and you can estimate the full capacity at 60 kWh (40/0.67 = 59.7). (But even there, the estimate is for whatever style of driving you were doing, because how much energy you get out of a battery depends on the discharge rate, so you'll get more kWh out driving slowly with modest demands than driving hard.)

 

[Vertiformed]

Here's some 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.

 

[enslay]

That 4.3 miles/kwh might lead you to believe that the GOM would display 4.3*65 ~ 280 miles. But your example shows 306. Another example that GOM does something more than just look at your average miles/kwh.

In fact, maybe just ignore miles/kwh on your driver console (because it's deceptive). There's an article on WIND-WORKS that shows a table of GOM estimates and miles/kwh. One extreme example is that GOM predicted 265 miles... even though the average efficiency was 3.3 miles/kwh.

With regard to the quoted section of OP.... DISCLAIMER: miles/kwh doesn't imply these values (e.g. mine shows ~208 for 4 miles/kwh... EDIT: oops! at 87% SOC, anyway, it's still below what I used to see at 87% for the 66kwh pack).

• If your recent 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 recent 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 recent 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

Why even post this bit? It's not true in general (even from your example).

 

[Vertiformed]

That 4.3 miles/kwh might lead you to believe that the GOM would display 4.3*65 ~ 280 miles. But your example shows 306. Another example that GOM does something more than just look at your average miles/kwh.

I said and underlined that the guess is based on your >>> recent <<< efficiency. It should be obvious that your average efficiency over the last 4000+ miles isn't recent.

Perhaps I shouldn't have circled that number on the dash display, but I think it helps for new owners to be realizing that miles/kWh is a thing.

 

[enslay]

I said and underlined that the guess is based on your >>> recent <<< efficiency. It should be obvious that your average efficiency over the last 4000+ miles isn't recent.

Perhaps I shouldn't have circled that number on the dash display, but I think it helps for new owners to be realizing that miles/kWh is a thing.

Well, the WIND-WORKS extreme example with 3.3 miles/kwh is after only 279 miles on odometer. I reset my efficiency profile and the GOM still low-balls it. It must be using more information than just that average.

EDIT: Basically, all I'm saying is that the miles/kwh doesn't relate to distance or battery capacity so obviously w.r.t. to GOM... because GOM seems to be doing something more sophisticated than just using the average to calculate your range. Either that, or my battery has problems! But your example and WIND-WORKS leads me to believe that GOM is just smarter than we think it is... as for the battery, it seems you have to use OBD2 or the napkin math you showed with discharge/SOC percentage change to estimate capacity. The latter estimate should be independent of how you drive.

 

[Vertiformed]

Why even post this bit? It's not true in general (even from your example).

Well, the WIND-WORKS extreme example with 3.3 miles/kwh is after only 279 miles on odometer. I reset my efficiency profile and the GOM still low-balls it. It must be using more information than just that average.

I think you misunderstood what I was saying, so I've I added some additional text to the original.

The car never displays the weighted average efficiency from the last 50 or so miles that it uses for the GOM display. It certainly isn't based on the efficiency number from the trip odometer, unless you luck out somehow and happen things (briefly) align.

 

[GJETSON]

If you've just become a new owner, congratulations!

This is a much better description of how the DIC on the Bolt works than anything GM has put out. This should appear on the infotainment screen when you start the Bolt. Much better than this stupid screen.

https://www.chevybolt.org/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.chevybolt.org/attachments/win_20190814_10_08_05_pro-jpg.26930/

 

[enslay]

I think you misunderstood what I was saying, so I've I added some additional text to the original.

The car never displays the weighted average efficiency from the last 50 or so miles that it uses for the GOM display. It certainly isn't based on the efficiency number from the trip odometer, unless you luck out somehow and happen things (briefly) align.

That's exactly what I thought. And I will be ignoring the driver console's miles/kwh value because, as you said, the GOM does something more sophisticated that is not actually related to the value shown on the driver console.

I like to hear that! Because with the battery mahem, and low-ball estimates from GOM, I just want to make sure there's no bad cell in the simplest way possible. And the GOM and driver console efficiency are the wrong tools (or not even useful tools) to infer anything about the battery health.

 

[OneEV]

I nearly empty range everyday and GOM is dead on ..based on that days driving.


The reason most people cant rely on GOM is that they take short trips...= not enough data for the GOM to be accurate

expanding on that thought.. If it is 70 degrees F and I drove 220 miles today and have 20 miles of range left I know that when I wake tomorrow GOM will be displaying right around 240 Miles and as long as it's another 70 degree day and I'm running just city like I did the day before ..it's going to be pretty darn close .



NOw on the other hand if I just put 30 miles on the car yesterday and averaged 3.2 miles /kWh GOM is going to display 190 some miles of range in the Morning .. I know that wont be right because GOM didnt get enough data to make an accurate calculation

 

[Vertiformed]

And the GOM and driver console efficiency are the wrong tools (or not even useful tools) to infer anything about the battery health.

Exactly. They are not good tools for making battery health inferences.

That said, if you know that your recent driving has never dipped below 4 miles/kWh, and your GOM display seems really low (as if your efficiency was less than 3 miles/kWh), that would be a red flag and a good reason to investigate your battery capacity (e.g., by doing a discharge test).

 

[Vertiformed]

The reason most people cant rely on GOM is that they take short trips...= not enough data for the GOM to be accurate

First, it's not about how reliable the guess is, it's about what it means. There could be someone for whom a prediction of 180 miles on a full charge is really accurate because every day they take the same trip, driving fast on the freeway and so their efficiency is low. My original post is for the person who sees 180 miles and thinks something is wrong with their battery because they think it should “contain 238 miles”.

Second, the reliability of the guess is based on how accurately the future matches the past. It's not whether or not you take short trips. It is true, however, that when people take their Bolt on a long vacation trip rather than a short daily commute, their driving will be quite different and the guess won't be accurate (the trip they're taking is radically different from recent driving).

FWIW, I live at the top of a hill, and the guess is always inaccurate. When I go to work (downhill), my Bolt quickly becomes optimistic about the world, and by the time I get home again (uphill) the Bolt is feeling pessimistic. And when I go on a hike up a mountain, thousands of feet above my home, its mood swings are even worse.

 

[Paul Gipe]

This would be a good post on the FAQ page or Sean Graham's AllEVInfo site.

Paul

 

[ARob]

This post was locked, OP aware, in order to keep it as a useful FAQ.