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Discussion Starter #1
This is a very modest trip by many people's standards (some people commute this distance!) but it is exactly the kind of trip you can do easily without ever stopping to charge (not even overnight) or feeling the slightest range anxiety. Also, trips like this still serve as a good test of the Energy Assist feature of the myChevrolet app (and its display in CarPlay) and the guidance given by abetterrouteplanner.com.

For this journey, from City A to City B, there was a distance of about 79 miles to travel, and an elevation drop of -1400 ft (which included climbing 850 ft higher than my starting point before descending to my destination). Most of it was freeway driving, but there was city driving for a few miles at the origin and several at the destination.

When I read trip reports from other people, there is often talk about people running the car without the A/C to save energy (and stewing as a result) or driving so slowly that you're a hazard to traffic. There may occasionally be a need for these kinds of extreme measures if you're on some kind of journey that's a real challenge to the Bolt, but I wouldn't make those kinds of compromises (I'd drive something else). Thus I follow the flow of traffic — if traffic is moving quickly, I move quickly too. And I'm going to be comfortable, so I'll run the A/C as needed.

Heading out, I began with a full charge (Battery Level Displayed =100.00%, State Of Charge HD Raw, 96.00%). I arrived 80.9 miles and about 1 hour 35 minutes later, with 19.5 kWh used (and with about 1.97 kW gained from the descent). So the average speed was 51 mph, and the efficiency was 4.15 miles/kWh (but only 3.77 miles/kWh if we factor in energy gained from the the descent). Checking the night before, Chevy's Energy Assist had suggested I'd arrive with 65% and abetterouteplanner.com had suggested I'd arrive with 64%. When I set out, Energy Assist in CarPlay was more optimistic, and early on it started to think I might arrive with 70%, and then kept revising its estimate downwards, towards the end even becoming a little pessimistic thinking I'd arrive with 64% (and actually for only a few seconds, 58%). In fact I arrived with the battery showing 66% (Battery Level Displayed = 65.88%, State Of Charge HD Raw = 66.51%).

Returning to the vehicle after it had been parked for six hours, the battery level had risen just a tad (State Of Charge HD Raw, 66.65), but when I set off to return today, two days later, it had dropped back a smidge (State Of Charge HD Raw = 66.57%).

Driving home, traffic was worse and I got routed back a slightly different way to avoid a jam, so it was 82.6 miles for the return journey, and 1 hour 37 minutes, with 22.1 kWh used (of which 0.83 kWh was spent running the A/C almost the entire journey, something I hadn't needed to do on the way out). So the average speed was again 51.1 mph and the efficiency was 3.75 miles/kWh (but an impressive 4.1 miles/kWh if we factor out the 1.97 kWh climb). The night before, Chevy's Energy Assist had suggested I'd arrive home with 25% and abetterouteplanner.com had suggested I'd get home with 24%, but on the day Energy Assist in CarPlay was more optimistic, thinking I'd get home with 26% and then guessing 27%, before hitting maximal pessimism of 24% at one point. I actually arrived home with 26% (Battery Level Displayed = 26.27%, State Of Charge HD Raw = 30.84%).

So, overall the trip used 41.6 kWh to travel 163.5 miles, for an overall efficiency of 3.93 miles/kWh and 2% of energy spent on A/C to keep the cabin nicely cooled. I used 73.73% of the battery, which seems to indicate a battery capacity of 56.42 kWh, but on the other hand, I used 65.16% of the raw battery capacity, which indicates a raw battery capacity of 63.84 kWh. If we say that only 92% of that is usable, we have a battery capacity of 58.74 kWh.

But rather than think about the battery, the takeaway I have are that
  • The trip could have been 200 miles round trip and I would still have returned with about 10% remaining (maybe a little less as it'd be the freeway part that would likely be longer, not the city driving at the end)
  • It's usually fine to run the A/C as much as you like and to drive with the flow of traffic (in fact, when you have a car ahead that you're following at a safe and sensible distance, it actually helps reduce drag).
  • Looking at the energy differences going out and back, I suspect there must have been some wind involved.
 

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Great write-up! I tend to drive a bit conservatively (59mph on expressways with 62mph speed limit) and have done some 250-mile round trips without a mid-trip recharge, but it does get a bit jarring towards the end. Maybe I'll write about that some time. One recent 350-mile round trip involved a single 40-minute pit stop at a service area's DCFC and I could still return home with about 3% charge left.

BTW, my displayed vs. raw battery assessment points to the 90% usable number being more closer to reality for my Bolt. The graph I plotted ends up at around 5% raw at 0% displayed, and when the DCFC stops charging the battery at 100% displayed, there's 95.29% raw charge. I can still push 1%p extra (raw) on an L2 charger while still being at 100% displayed, so I'm actually able to use 91% with L2, versus 90% with DCFC.
 

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Wow. I've never driven my Bolt EV down to a 3% SoC. I was a little close tonight when I had 12 miles left and just one bar showing. Twelve miles is ~ 5% (3 kWh * 4 mi./kWh). I rarely cut it this close, but knew the route home and charged (AC Level 2) at a Hampton Inn (good guys, patronize them!) just enough to make it.

Teach me something here. I know about "drafting" and would never follow that closely. So is there a (safe and sensible) distance behind a car ahead which is NOT drafting but still gives you an advantage by reducing drag (i.e. "blocks" the wind or moves the air out of the way like following in the wake of a boat)?
 

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What kind of outside air temps did you have for the trip? Also, you listed that you gained some electrons on a descent, how did you quantify that? I'm thinking you were able to see that with your ODB thingy? I'm about to take my annual drive up north, I've been seeing 2.8kW/m on the Bolt display on the cold days so I put in 2.8 as a reference consumption and it has me stopping in Appleton, the 108 mile mark, arrving with 31%. I don't have the ODB stuff, but would like to post my trip when I take it in a few weeks. My route is flat, but I drive in 'L' typically. Thanks for sharing.
 

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Discussion Starter #5
Teach me something here. I know about "drafting" and would never follow that closely. So is there a (safe and sensible) distance behind a car ahead which is NOT drafting but still gives you an advantage by reducing drag (i.e. "blocks" the wind or moves the air out of the way like following in the wake of a boat)?
I don't know how well it has been studied, but I observed from my drive to work each day how freeway conditions seemed make a difference to how much energy I used. I found that when there was a car ahead of me I used less energy than than when I had empty road. I'm sure tailgating would increase the effect, but I stay back at a sensible following distance where I still have a reasonable time to react.

I've not done a systematic study, but as a result I don't feel so bad driving behind some kind of behemoth (i.e., SUV or pick-up truck), although I also don't mind if it's something smaller as that way I have a better view ahead.

My overall attitude is, in traffic, I keep up. With an open road, I drive at a pace of my choosing, which is usually a little bit slower.
 

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Discussion Starter #6
What kind of outside air temps did you have for the trip? Also, you listed that you gained some electrons on a descent, how did you quantify that? I'm thinking you were able to see that with your ODB thingy? I'm about to take my annual drive up north, I've been seeing 2.8kW/m on the Bolt display on the cold days so I put in 2.8 as a reference consumption and it has me stopping in Appleton, the 108 mile mark, arrving with 31%. I don't have the ODB stuff, but would like to post my trip when I take it in a few weeks. My route is flat, but I drive in 'L' typically. Thanks for sharing.
It was probably 90 ℉ outside on the way back, with the sun beating in.

My ODB-II thingy is this one, the LELink^2, which works well with iPhones (and Android too, but iPhones are the fussier ones).

For the energy from descent, there is a link in the original post to the Wolfram Alpha calculation (gravitational potential energy) — you just need the weight and the change in height.
 

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For the energy from descent, there is a link in the original post to the Wolfram Alpha calculation (gravitational potential energy) — you just need the weight and the change in height.
Ok, thanks, I saw that the energy was highlighted, but I just stupidly assumed the board here did that and it wasn't a hyperlink.
 

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It was probably 90 ℉ outside on the way back, with the sun beating in.
My ODB-II thingy is this one, the LELink^2, which works well with iPhones (and Android too, but iPhones are the fussier ones).
For the energy from descent, there is a link in the original post to the Wolfram Alpha calculation (gravitational potential energy) — you just need the weight and the change in height.
I just ordered the thingy so I'll have it for my upcoming trip.
 

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Wow. I've never driven my Bolt EV down to a 3% SoC. I was a little close tonight when I had 12 miles left and just one bar showing. Twelve miles is ~ 5% (3 kWh * 4 mi./kWh). I rarely cut it this close, but knew the route home and charged (AC Level 2) at a Hampton Inn (good guys, patronize them!) just enough to make it.

Teach me something here. I know about "drafting" and would never follow that closely. So is there a (safe and sensible) distance behind a car ahead which is NOT drafting but still gives you an advantage by reducing drag (i.e. "blocks" the wind or moves the air out of the way like following in the wake of a boat)?
I tend to draft behind taller vehicles such SUVs or semis for a couple of reasons:

1) The drafting creates an air current over and around your smaller vehicle especially with semis.
2) The larger vehicles take longer to stop so there is little chance you will rearend them in the case of an emergency stop. Remember the old 2 second rule of following? Just make sure you are always alert as to the vehicle ahead of you when drafting.

To find your comfort zone when drafting, follow a vehicle and crack both of your front windows. Listen to how loud the wind is when you are out front as opposed to drafting. That is the wind resistance you are driving against.

I've done this on my Harley behind a semi. Result: complete calm and no wind turbulence.
 

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I tend to draft behind taller vehicles such SUVs or semis for a couple of reasons:

1) The drafting creates an air current over and around your smaller vehicle especially with semis.
2) The larger vehicles take longer to stop so there is little chance you will rearend them in the case of an emergency stop. Remember the old 2 second rule of following? Just make sure you are always alert as to the vehicle ahead of you when drafting.

To find your comfort zone when drafting, follow a vehicle and crack both of your front windows. Listen to how loud the wind is when you are out front as opposed to drafting. That is the wind resistance you are driving against.

I've done this on my Harley behind a semi. Result: complete calm and no wind turbulence.
I thought two seconds behind was a great enough distance to allow the "semi-displaced air" to "refill the void" and negate the drafting effect. On my road bike, I have drafted behind a logging truck going downhill. I was less than 20 feet behind and it was exhilarating if not a little scary. Never this close in a car, though.
 

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Gotta say I’ve done the same behind a semi. On a bike behind a semi is ok that close because when the semi brakes, you have time on a bike to dismount, check your tires, get some lunch, and mount up again before you have to brake! Lol! Or something like that. Just gotta make sure you’re awake and paying attention when that close.
I tried seeing how close I could get to a semi in the Bolt but the front collision lights kept going off even at the closest setting. Auto bakes even came on a couple of times showing they actually function!
 

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Discussion Starter #14
Here's a graph for cyclists related to drafting.

Image result for air resistance drafting distance graph


But an SUV at 75 mph isn't a bike at 20 mph, so the savings should be bigger at the distances given above. Of course, if you follow the 3-second rule, you should have 110 yards (22 car lengths) between you and the car in front at 75 mph, whereas if you adopt the 2-second rule, it's 220 feet (or 15 car lengths).

I'm not sure what the average distance is between cars on the freeways I travel. It feels like 15 car lengths would be a very generous gap in a lot of the traffic I drive in. I actually now want to go take some measurements.
 

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Discussion Starter #15
(Looking at my local traffic cameras, it seems to me like plenty of traffic is driving closer than 15 car lengths.)
 

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Discussion Starter #16
Doing a bit more homework, I found: “The normal safety guideline is that a driver should leave one car length between his or her car and the car in front of it for every 10 mph. So, to be safe, a car traveling 60 mph should normally have at least six car lengths of empty space between it and the car in front of it.” That turns out to be the “one second rule”.
 

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Ditto Vert, I also would rather take an ice if I'm getting to that type of trip where I'm sweating rather than running climate control. I don't mind running slow in the slow lane so much, as long as there is some other slow guys to buffer. Its rare there is not any around here IME.

Unloaded semis can stop a lot faster than loaded ones.. you can tell if they are loaded or unloaded by how they bounce around. Not that I advocate tailgating.. For what its worth usually the ones NOT doing it in this area are in the minority. As the cameras show.
 

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Discussion Starter #18
@hatchy, from various videos (and perhaps actually in-person witnessed events, I'm not sure), even loaded semis can often stop surprisingly quickly.

I hadn't considered my own “following mode” driving to be tailgating, but possibly I should be hanging back further. I know I never make the follow-distance dash indicator go amber (except sometimes briefly while merging in adversarial traffic). Looking in the manual, however, I note that the dash light only goes amber when the car considers you “much too close”, which is little help really. I'm going to investigate a little more to see what I'm actually doing in practice.
 

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I note that the dash light only goes amber when the car considers you “much too close”
Mine goes amber when someone pulls in front of me and takes up what was my 2 second following distance.
But someone posted this awhile back about the benefits of letting people take your gap:
 
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