How can I determine what the optimal speeds and charging stops are for a particular trip?

A Better Route Planner is one tool. An a energy assist tool in the Chevy app. When running the numbers, sometimes it's better to drive as fast as you can. The battery charges faster when at a lower level of charge. All depends on the spacing of the chargers.

Is "A Better Routeplanner" Better? A Review...

Is "A Better Routeplanner" Better? A Review for the Bolt There are four route planners I've used for planning trips in our Chevy Bolt. I've reported on my experience with EV Trip Planner, Green Race, and Chevy's own Energy Assist App. The first two are found on the web, the latter is...

www.chevybolt.org

 

Where is the Energy Assist Tool in the app?

 

How significant can the time savings be on an 8-hour trip?

 

Some Long-Trip Travel Time Graphs & Numbers

(I originally posted a preliminary version of this post deep in another thread, but on reflection I think it deserves its own post.) In the best case, how fast can you get from A to B in a Bolt? (in the best case scenario) Here are some graphs that answer that question! First, a summary of...

www.chevybolt.org

 

Technically, what Rob said is correct: "Sometimes." But you can find a corner case for anything. However, under normal and reasonable conditions, what he said is untrue. On long trips, driving makes up the lion's share of time, so a 10% reduction in time spent driving (i.e., driving faster) will outweigh a 20% to 30% reduction in time spent charging.

As an extreme example, Hyundai recently did a publicity stunt where they drove a couple of Hyundai Kona Electric's over 600 miles on a single battery charge, bringing their time spent charging down to zero. The only catch? It took them 35 hours of driving to do. By contrast, I could drive my Bolt EV 300 miles on a battery charge at 45 to 50 mph, stop and L2 charge up over night, and drive another 300 miles at 45 to 50 mph. When it's all said and done, I would have driven the same distance in half the time.

 

So basically what I'm wondering is whether there is any possibility of time savings on a trip from Athens, GA to Danville, KY and vice versa. I have done that trip in about 9 hours, driving about 9 mph over the speed limit, and stopping at the EA stations in Kennesaw, Chattanooga, Knoxville and Willamsburg. Could I possibly save any time overall by driving slower and/or stopping at slower chargers? What if I do the trip through South and North Carolina, stopping at the EA stations in Commerce, Greenville, and Asheville instead of Kennesaw and Chattanooga?

 

I suppose it depends, but that seems like an awfully long time to complete that trip. It should be less than 7 hours driving time when going the speed limit, and it's less than 400 miles, meaning the Bolt EV should need two 30 to 40 minute charging sessions at most to complete the drive.

 

ABRP shows the trip is 355 miles, 8 hours and 15 minutes including 2 charging stops, 26 minutes and 23 minutes.

 

I did a while ago some math for 500e.
Turned out it is better for me to drive faster on highway speed (70 mph) than going via city/suburbs 50 mph.
However, that applied to WINTER condition. I did not take charging into consideration. It was only due to the fact the cabin heater must pump energy into the car. So going faster I use more energy per minute, but over time and energy spent is more when driving slower.

 

I did the math once based on a questionable chart that plotted energy consumption at various speeds, and concluded 75 MPH was the optimal speed, but that assumed charging locations exactly where you needed them...

I'd say if you will be close to being able to skip a charging session, then slowing down will probably overall be faster, but if you can't skip a charging session, just drive faster.

*all of this is theoretical since I don't own an EV. Newscoulomb is experienced in this regard.

 

I'd say if you will be close to being able to skip a charging session, then slowing down will probably overall be faster, but if you can't skip a charging session, just drive faster.

This is a good summary, and generally true in my experience. Today, we only have a sparse network of chargers. I am able to get anywhere I want to go using DCFCs, but that is not the case for everyone. And I often have to hit certain chargers to make it. In those cases, driving faster (but not so fast that I cannot make it) actually saves times.

It's a moot point for me, since I drive at the posted speed limit anyway. But I don't begrudge those who want to drive faster; that's what the left lane is for. (I do begrudge those who want to drive faster but refuse to pass and just tailgate instead).

 

I understand where the idea comes from, but in "normal" conditions, driving the speed limit and adding charge stops is generally going to get you there faster.

I recently did a 236 mile each way trip in the CO Rockies. The return trip was done without a charge stop and I arrived home with 7% SOC, 4.8 miles/kWh.

The primary factor than enabled me to get such a high MPK was the typical weekend traffic returning to Denver. From Silverthorn, you climb up to ~11K feet elevation at the Eisenhower tunnel, then it is all downhill to Denver, roughly 5000-6000 feet elevation drop, averaging about 30MPH with traffic. My range entering the tunnel was 58, and reached 110 when it got to the Denver metro area. I regenerated about 3-4kWh on that 40 mile stretch, enough to get me home at 55-65 MPH.

Had this leg not been congested (rare on weekends), I surely would have needed a stop somewhere in the Denver area, and that might have been a 15-20 minute stop. But, I probably would have cut 30-45 minutes on the trip due to the higher speeds.

 

I've done a couple very long trips in my Bolt. I learned that owing to the need to frequently leave the highway, get to the L3 station, deal with charge initiation, wait for the charge, and then resume interstate travel, my 'speed made good' is just over 40 mph. In an ICE, that figure is 60-65 mph (Cruise at 70-80 mph with much fewer and much shorter fuel stops). That's a huge difference.

BTW, over at Voltstats, I'm the current champ in miles driven in 24 hours - 933. For whatever reason, that number is low...we actually managed just over 1000 miles in 24 hours on a run from north Florida to the Boston area...I don't know what went wrong, but I have a spreadsheet that includes EA charging stop records to support the claim of 1000+miles

I relate that only to make the point that the Bolt really isn't suitable for long range road trips.

Another data point - I live in north Florida, but to get a break from summer humidity I head to Beech Mountain, NC. The trip is right at 500 miles, doable in an ICE in around 8 hours. Out of curiosity, I ran the numbers at ABRP...for a long range Tesla, the trip is about 9-1/2 hours with two charging stops. for a Bolt, the time is 12 hours with 4 or 5 charging stops, each of which is longer. That's exactly in keeping with my own experience that a Bolt can average no more than 40-42 MPH in very long distance travel.

I still love my Bolt (just bought a 2nd one off lease for my daughter), but It is very much limited compared to both ICE cars and Teslas for long haul travel.

 

BoltStats! resets at an odd time, so you can't get a true 24-hour run unless you start or are already driving when the counter resets. I can't remember what it is, but it's like 4 AM EST or something like that. I'm impressed you could make it 1,000 miles in 24 hours if your overall speed was ~40 mph. That means you were driving the entire time.

The 1,100 miles I did in the 2020 Bolt EV was about 22 hours (6 am to 4 am the next morning). I've been tempted to do a 24-hour challenge in my 2017 Bolt EV, but I'd really need to make the time to do that. My projections are that I should be able to do at least 1,200 miles based on my typical ~50 mph average trip speeds including charging stops, but a lot can happen in 24 hours and 1,200 miles of driving.

Compared to an ICE, though, yes, that's slow. In my Volt, I can average closer to 70 mph on long trips if I'm willing to forgo meal stops.

 

Amazing how times change. The Bolt will average about what I used to be able to do in my old Vega when the national speed limit was 55 mph. But the Bolt is a rocket ship compared to that Vega. I used to plan my trip times by multiplying every 100 miles by 2 hours. So a 600 mile trip would be 12 hours. Maybe I can use that same method for traveling in the Bolt.

 

For me, the shorthand is 3:1. The Bolt EV with typical freeway speeds and charging rates will average a 3 to 1 ratio of driving to time spent charging. So if you are traveling 600 miles, expect to spend about 8 hours 30 minutes driving and
a little less than 3 hours charging.

If you drive over 80 mph or faster, expect the charging time to spend a greater percentage of the overall time, but you'll still spend less time driving and less time overall.

If you drive slower, you could potentially get the ratio as low as 5:1 or 6:1 driving to charging time before things get unreasonable (e.g., driving 45 mph on the freeway).

 

I have found that 65mph has been the best practice for me. I also run 40psi in my tires. This gets me 4.1m/kw jumping to 70mph drops it to 3.7/3.8 m/kw. I have a mix of hills and flats on a round trip so it balances out on terrain. These numbers are an average in 70° and warmer with little no wind, Radio the only accessories on.

 

I love torque maps... I wish they were readily available for all engines in all manufacturers as frankly, for me, this is one of the main deciding factor for purchase of a certain car.
And the power/torque graphs. Darn it. So normal to get this info in Europe, but not in the US. Why?
Funny fact I noticed - in Poland, when I would read an ad about some car, they would say how big is the trunk, what is the power of the engine, what is the fuel economy... in the US the first thing (at least couple of years ago) it was about: how many cup holders, how many speakers, then mpg, maybe how many cylinders.
To find out what is the torque - well, it takes a while. To see the power curve - almost impossible. Ask you dealer.


Anyway, whatever a professors says, or some other graphs - my own tests. Based on 1 example. No error bars here, no standard deviation.
Bolt at 70 mph will do about 3.6 mil/kWh
At 50 mph will do 5.0 mil/kWh.

Q5 at 70 mph will do 28 mpg
at 50 mph will do 35 mpg.

That is summer, no AC use in either case.

Winter? Heck, who knows. But, Q5 will not be affected much, while Bolt - I guess I could estimate assuming 4 kW energy needed to heat the cabin.
My numbers would be like that then:
3.0 vs 3.6 (70 mph and 50 mph respectively)
Interesting how big impact it takes at lower speeds.

 

Winter? Heck, who knows. But, Q5 will not be affected much, while Bolt - I guess I could estimate assuming 4 kW energy needed to heat the cabin.
My numbers would be like that then:
3.0 vs 3.6 (70 mph and 50 mph respectively)
Interesting how big impact it takes at lower speeds.

The rule of thumb I've read on hypermiler and ecomodder forums for ICE cars is ~6% efficiency loss for every 10 F the temperature drops. If you go to some of the mileage/fuel economy tracker websites and compare the fuel economies of the same vehicles in, say, Canada versus Florida, you'll see a noticeable difference in fuel economy.

 

Yeah 6% per 10 degrees F isn't right, and as you point out, it depends on how cold things were and how far the vehicle is driven.

I know people that would commute 3/4 of a mile daily. A car doesn't even warm up in that distance. Engine coolant, transmission/gear oil, and engine oil all cause more drag when cold, but the biggest consumption comes from the vehicle running at high idle and rich during the warm up phase. My Prius would run high idle until it reached an engine coolant temp of 130 F. That was probably 3 minutes.

 

The other thing to note during autumn and winter is that lower ambient temperatures cause reduced tire air pressure that worsens economy, unless the owner is vigilant about checking tire air pressure, particularly during autumn.

 

If there are no chargers or no working chargers then going slower would definitely be faster due to the reduced walking (or maybe running) time at the end. Also if you have to drive a long distance out of your way to get to the charger, going slower might be faster if it makes using the shorter route possible.

 

Just my observations in 2 years plus with my Bolt. Driving on the interstate @ 70 mph uses about 20 kWh/h so about 3 hours and 210 miles range, hypothetically speaking, of course. Driving on state roads @ 55 mph, I can get about 15 kWh usage so about 4 hours @ 55 mph = 220 miles but driving back roads @ 45 mph, I can get about 10 kWh usage or about 260 miles range. I avoid the interstate whenever I can because I'm cheap, and I'm also retired, and in no rush. Until the infrastructure of charging stations changes, the BEV's are still better at city driving than long distance touring.

 

Today, Chevrolet Program Engineering Manager Rob Mantinan said, "Sometimes driving slower gets you there faster." Meaning that driving slower extends your range and might possibly allow you to skip a charging stop.

I find that this can be true when the high-speed freeway route is a longer distance than a route along secondary roads. It can also be true if driving fast would cause an extra charging stop, but the needed charger is not directly on your path.

 

Spent an hour thinking about this.

Assumptions. 500 miles trip. Soc 10% to 55% so as to get the top 53kw charging rate. Efficiency 4.4 miles / kWh at 63mph, and is inverse proportional to square of speed.

Cut away the math equations. Here is the short version of the story.

80mph. 6 charges. 9.2hr. 183kwh.
75mph. 5 charges. 9.2hr. 161kwh.
70mph. 5 charges. 9.7hr. 140kwh.
65mph. 4 charges. 9.7hr. 120kwh.
60mph. 3 charges. 9.9hr. 103kwh.
55mph. 3 charges. 10.6hr. 72kwh.

Conclusion. I will continue to drive at 65mph. 30min more, $20 less. It is pretty expense and time consuming to drive EV for road trip.

-TL

Sent from my SM-N960U using Tapatalk

 

Spent an hour thinking about this.

Assumptions. 500 miles trip. Soc 10% to 55% so as to get the top 53kw charging rate. Efficiency 4.4 miles / kWh at 63mph, and is inverse proportional to square of speed.

Cut away the math equations. Here is the short version of the story.

80mph. 6 charges. 9.2hr. 183kwh.
75mph. 5 charges. 9.2hr. 161kwh.
70mph. 5 charges. 9.7hr. 140kwh.
65mph. 4 charges. 9.7hr. 120kwh.
60mph. 3 charges. 9.9hr. 103kwh.
55mph. 3 charges. 10.6hr. 72kwh.

Conclusion. I will continue to drive at 65mph. 30min more, $20 less. It is pretty expense and time consuming to drive EV for road trip.

-TL

Sent from my SM-N960U using Tapatalk

Based on your own numbers and Electrify America's current 31 cent per kWh pricing, it saves 30 minutes going 75 mph over 65 mph, and it only costs $6.51 more. Basically, it's a question of how much your time is worth. Also, based on your numbers and starting with a full charge at the national average electricity rates: At 65 mph, it will cost less to make the trip in a Bolt EV than it would to take a 50 mpg gas car with $3.00 per gallon gas prices, so "expensive" is relative.

 

Second thought. It may not be a good strategy to stay below 55% soc. Even at tapered down charging rate of 16kw, it is still equivalent to 70mph. I will rerun the numbers with different soc limits.

-TL

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I have been assuming that the car has been charged to 55% leaving home. 120kwh is all from charging on the road. That makes the analysis easier.

-TL

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Then your numbers don't work. 33 kWh + 120 kWh to travel 500 miles at 65 mph would mean an efficiency of less than 3.3 mi/kWh, which would be more accurate for 70 to 75 mph driving. With an average driving speed of ~70 mph, my typical consumption is about 145 kWh for a 500-mile trip. An average driving speed of 65 mph would be significantly more efficient. 120 kWh would probably be overly optimistic, but 153 kWh is completely unrealistic. Also, leaving home with 55% battery is unrealistic. It might make sense if you have no access to charging at home, but even then, you'd still want to leave with at least 70% battery.

It appears that you're trying to manufacture circumstances in which an EV would be more expensive to take on a long trip than an ICE car, but the numbers just don't support it.

 

Nope. Going above 55% won't help total traveling time. But you can actually arrive earlier by driving slower if you always charge up to 80%. The charge time is about 1 hr.

-TL

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Efficiency at 65mph is 4.13 miles / kWh. 500 / 4.13 = 121 kWh. It charges 4 times. Each time is 27kwh. When it arrives, the soc is above 10%.

It is wrong for me to say that the total energy is from charging on the road. It does uses the charge from home charging.

The electricity expense for such trip is the 27*0.19+(121-27)*0.31=$34.

We good?

-TL

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Efficiency at 65mph is 4.13 miles / kWh. 500 / 4.13 = 121 kWh. It charges 4 times. Each time is 27kwh. When it arrives, the soc is above 10%.

It is wrong for me to say that the total energy is from charging on the road. It does uses the charge from home charging.

-TL

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To make that work, you're assuming that you're starting at 0%. Most Bolt EV owners will start with at least 50 kWh of energy "in the tank." So a 500-mile trip at 65 mph (I think ABRP's collected data had the Bolt EV's efficiency at 65 mph at 3.87 mi/kWh) would require charging 70 kWh (your numbers: 120 kWh minus 50 kWh) or 79 kWh (ABRP's numbers: 129 kWh minus 50 kWh) at public DCFC in order to complete the trip. At Electrify America's current 31 cents per kWh, that's $21.70 (your numbers) to $24.49 (ABRP's numbers). Again, that's assuming you're leaving with 80% to 90% battery, which would represent less than 60 kWh including losses ($7.96 at the national average electricity rate of 13.26 cents per kWh).

Say an ICE car with the Bolt EV's size and format got 40 mpg at freeway speeds (a stretch, but we'll go with it) at the national average $2.20 per gallon, the 500-mile trip would cost $27.50. I'm not seeing a huge difference in cost there, and that's after working very hard to put the ICE car in its best light.

 

Ok. Let's do it the other way.

The car is charged to 55%. I drive 112 miles to 10%. Then I charge to back to 55%, and continue to drive. I do this 4 times. When I arrive with 23% soc. Does it work?

I almost bought a Hyundai accent for $15k instead of the bolt. It does 40mpg. With all the subsidies, I think I paid $23k for the bolt. $8k can buy 2700 gallons of gas, or over 100k miles. Not to mention, saving of 2 hours for each of the trip.

-TL

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You're still not addressing why you need to leave with just over half a battery. Just so a majority of the charging is done at a higher cost? Anyway, yes, that would increase cost and time.

As for the Hyundai Accent, you're talking about a significantly smaller car. The trunk area is over 3 cu/ft smaller than the Bolt EV's, and the Accent has far, far less capacity with the seats down.

 

When DCFC chargers are available everywhere and all the time I'll drive to 5% battery. Actually not. Sometimes stuff happens. I was once driving south on I-35 through OK (Volt at that time) when a landslide closed the Interstate. Multihour detour (they routed over a 2 lane bridge under construction so it was 1 lane with alternating one way traffic). Terrible time to have planned out a get there by the skin of your teeth refueling stop.

 

Exactly. In my experience, the worst backups occur in winter. Often tractor-trailers T-bone on black ice, blocking the entire interstate for hours. I would hate to have to turn off my heat when it's sub-zero out because otherwise I won't make it. In fact, letting the car cold soak for hours will lose all of the precious heat in the battery and drive system, making it less efficient. Even if you turn off the car, you may find that when you turn it back on, you can no longer make it to the charger. And now you need a tow truck to add to the existing mayhem.