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I have heard that the Bolt has very good regen, maybe even better than Tesla's. But I haven't heard how efficient it is. Do you get 80% of the energy back into your battery? 50%?

I can imagine doing a test where you record the battery charge, drive up a long hill and then regen all the way down--say a distance of 5 miles. Then record the battery charge again. Add back the charge you would consume driving 5 miles on the level, and then I would think a comparison of the starting and ending battery charge would provide a measure of regen efficiency. Is that a valid way to think about it?
 

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I have a bolt and a Tesla and just sold a Leaf. Unsciencticly I state the Bolt has better regen.. I can drive the Bolt and usually never touch the brake. Tesla has good regen, but it wont take the car to a dead stop. I think I read it was due to the type of motor used. Leaf regen sucked.
1- Bolt
2- Tesla
Last- Leaf
 

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I saw a vid on YouTube where the owner drove up a long hill at freeway speeds and on the drive down the other side he gained more miles than he had starting up the hill. Just can't remember the name of the vid to try pulling it back up.
 

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I saw a vid on YouTube where the owner drove up a long hill at freeway speeds and on the drive down the other side he gained more miles than he had starting up the hill. Just can't remember the name of the vid to try pulling it back up.
The challenge to checking this is that the estimated mile efficiency can change. If Chevy would tell us in kWh, how many are in the battery, then up and down hills would tell the story. Qualitatively, it seems very good. I live at 920 ft and often drive down town (about 200 ft elevation) then back up and the overall trip mileage seems to correspond with the range. Actually, since the Bolt tells you how many kWh have been used, I guess just monitoring that and subtracting would give a good indication. To me the regen is one of the joys of the Bolt, since with an ICE, all of that energy going down hill just goes to waste. It was why my Jetta that should have gotten about 28 mpg, was getting about 20.
 

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I can drive the Bolt and usually never touch the brake.
There's a big difference between how aggressively the car slows down with regen and how efficient it is. The OP is basically asking the question: How much less energy is put into the battery by using regen to slow down 10mph compared to the amount that is taken out of the battery to accelerate by the same amount?
 

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I don't have any scientific, factual numbers to post, but I can tell you that I think it's pretty dang efficient. I have gone up and down some pretty steep hills now and I'm pretty amazed at how going up the hill I watch the life being sucked out of the battery, but then going down the hill, it magically mostly comes back!

I have also been impressed at how the estimated range doesn't go down hardly at all in stop and go traffic. It starts to seem like a nearly free ride! Sadly, once the traffic picks up and you get back to freeway speed, that's when the free ride ends.:(
 

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I don't have any scientific, factual numbers to post, but I can tell you that I think it's pretty dang efficient. I have gone up and down some pretty steep hills now and I'm pretty amazed at how going up the hill I watch the life being sucked out of the battery, but then going down the hill, it magically mostly comes back!
Are you really looking at the battery (charge level)? Because if you're looking at the guessometer, what you're seeing is the effect of the estimation formula, not the battery charge level.
 

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Are you really looking at the battery (charge level)? Because if you're looking at the guessometer, what you're seeing is the effect of the estimation formula, not the battery charge level.
Yes, just the guess-o-meter. I really don't need anything to shatter my illusions of love. Like I said, it's all appearance and non-scientific, just feel good. To me, all that matters is how many more miles I can go. I really have no idea how efficient the system is.
 

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I saw a vid on YouTube where the owner drove up a long hill at freeway speeds and on the drive down the other side he gained more miles than he had starting up the hill. Just can't remember the name of the vid to try pulling it back up.
It is not possible to regain all the energy used to go up a hill then back down (for example climbing to the top then turning around and regen-coasting back to the starting location (elevation). The laws of physics are at work here; if it were possible then the Bolt would be a perpetual motion machine, which does not exist.
 

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It is not possible to regain all the energy used to go up a hill then back down (for example climbing to the top then turning around and regen-coasting back to the starting location (elevation). The laws of physics are at work here; if it were possible then the Bolt would be a perpetual motion machine, which does not exist.
It's entirely possible the drive down the other side was longer than the uphill in the vid. Been a while since I've watched it.
 

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If the OP is looking for a % recaptured, the answer is - it depends.

Regen will be less efficient at higher speeds. Lifting off the accelerator at 70 mph, air and rolling resistance scrub off lots of speed with no recapture at all. Try keeping a neutral throttle (no energy use or regen) at 60 mph on a flat road and your speed will decrease.

Cold, wet weather at sea level also creates more drag than a hot dry day in Denver.

A full battery (or one that is either hot or cold) will have lower limits on the amount of charge it will accept.

The "charging losses" from the motor to the battery are likely at least 10%. Other losses will vary with conditions.

MPGe can give some indication of regen efficiency (for similar cars - don't compare a Model X to a Spark EV). Small hatches that get in the 120 range (Bolt, i3, eGolf) likely have better regen than those with lower scores (the LEAF scores 112). The IONIQ score 136 and I would expect very good regen from it.
 

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If anything, one can regain (a percentage of) energy used to increase speed or elevation. But one can never regain energy used for traveling distance.

As we are not able to separate out these two types of energy consumption, regen efficiency wil never get even close to 100% when comparing "# of bars at start of ascent to # of bars at end of descent"
 

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The home screen has a widget that displays kWh consumed and distance traveled since last full charge. The kWh number does go down when going down a hill, and obviously increases while normally driving. Should be really easy to take note of that number before going up a hill, take not of the number at the top, and again at the bottom of the hill, and come up with a ball-park figure for regen effectiveness, both in D and L.
 

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But one can never regain energy used for traveling distance.
Sure one can. If I travel a mile at 90mph, neither gaining nor losing speed or elevation, then slam on the regen paddle, I will regain some energy used.

But I agree with your larger point that the OP's proposed experiment can not succeed in estimating regen efficiency.
 

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Sure one can. If I travel a mile at 90mph, neither gaining nor losing speed or elevation, then slam on the regen paddle, I will regain some energy used.

But I agree with your larger point that the OP's proposed experiment can not succeed in estimating regen efficiency.
This post would be too long to detail out properly why I disagree here. Obviously, you can not regain the energy being used (read:consumed) to travel a distance. You can regain most [this is what I believe the poster is looking to define] of the energy used to accelerate the vehicle prior to travelling the distance (if we remove external influences on the vehicle). Energy is used for additional things such as friction (road, air, internal components like bearings), heat, other electrical inefficiencies, and even noise - to name a few.

To try to answer the poster's original question; see my limited research below. This is not specific to the bolt (particularly the Tesla roadster) but I doubt that the bolt regen efficiency is 'much' better. I found another source that said 70% was about as efficient as they found possible based on gearing. Also, consider that the strength of the regen that you feel, really is not related to how efficient it is, just how quick it is at converting kinetic energy back to electrical to chemical. My point being that even though it feels different from other vehicles' 'weak' regeneration, it doesn't mean it is actually more efficient. <insert some disclaimer here about how I could be completely wrong>

From: https://www.tesla.com/en_CA/blog/magic-tesla-roadster-regenerative-braking

"How much energy does it recover?

Unfortunately, the adage “your mileage may vary” applies to regen as well. The amount of energy you can recover depends on how and where you drive. From the powertrain point of view it looks pretty good. The energy conversion efficiencies from chemical to electrical (battery), DC current to AC current (inverter), electrical to mechanical (motor), and torque to force (transmission and wheels) are all quite high and work just as efficiently returning energy into the battery. The bigger problem is aerodynamic losses and higher speeds and rolling friction of the tires. These both act to slow the car, but the energy dissipated cannot be recovered. We must also remember that, even though the battery-to-wheel conversion efficiency is pretty good (up to 80% or so), the energy makes a full circle back into the battery and it gets converted twice for a net efficiency of at most 80% * 80% = 64%."

They have more information on this website and I encourage you to do your own research as well.
 

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Seen that car makers producing supercars started to make cuts throughout the body in a way to single out the immediate areas that the driver and passenger need to be in. It goes a long way with design, maybe thats what we''ll see with a future Chevy EV product.

Already the Ford GT and BMW i8 has this.
 

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This post would be too long to detail out properly why I disagree here. Obviously, you can not regain the energy being used (read:consumed) to travel a distance. You can regain most [this is what I believe the poster is looking to define] of the energy used to accelerate the vehicle prior to travelling the distance (if we remove external influences on the vehicle). Energy is used for additional things such as friction (road, air, internal components like bearings), heat, other electrical inefficiencies, and even noise - to name a few.
Exactly. Some energy is converted into kinetic energy. This can be recovered to some extend. Some energy is converted into (ultimately) heat. This cannot be recovered. At least not by the car.

To try to answer the poster's original question; see my limited research below. This is not specific to the bolt (particularly the Tesla roadster) but I doubt that the bolt regen efficiency is 'much' better. I found another source that said 70% was about as efficient as they found possible based on gearing. Also, consider that the strength of the regen that you feel, really is not related to how efficient it is, just how quick it is at converting kinetic energy back to electrical to chemical. My point being that even though it feels different from other vehicles' 'weak' regeneration, it doesn't mean it is actually more efficient.
I would say it is likely to be the other way around: stronger regen results in higher currents and thus more heat and thus more losses in the process ....
 

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Exactly. Some energy is converted into kinetic energy. This can be recovered to some extend. Some energy is converted into (ultimately) heat. This cannot be recovered. At least not by the car.
Good luck identifying exactly 'which' energy was used for acceleration, and which energy was used to maintain speed over distance through friction, rolling resistance, etc. And then tracking each energy type separately as it exits the battery and later re-enters it via regeneration.

There is not nearly enough precision of language in any of these posts to make further discussion profitable, beginning with the fuzzy concept of 'energy used for traveling distance', which becomes zero - when you later argue that it is not used for traveling at all, but instead is used for friction and heat.:)
 

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We all know only one kind of energy can leave the battery. But I assumed everybody would understand I was talking about how much of energy is used for maintaining speed over time (traveling a distance) versus how much energy is used for accelerating. Especially since I wrote 'some energy' and not 'some kind of energy'.

BTW: Also electrical energy converted into potential energy (by gaining altitude) can be recovered to a certain extend. But again, this excludes energy used for traveling distance.

To make it simple: if we speed up over a short distance and slow down immediately, again over a short distance (or climb a short steep hill and steeply descent the other side), we can recover a fair percentage of the energy we spent. But we will not have traveled a large distance. When we on the other hand speed up (or climb a hill), travel a 100 miles at constant speed and then slow down again (or descent the hill), we will have traveled a large distance, but we can only recover a very small percentage of the total amount of energy we spent.

Altogether the percentage of energy spent that can be recovered large depend on what you spend it on. When talking about regen efficiency we should talk about how well kinetic (speed) or potential (altitude) energy stored in the car can be converted back into electrical energy in the battery.
 

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Too bad EV car makers are not using solar panels on the body since even something simple as a solar roof would do us a lot of good. Not only that but it will look cool.
 
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