[RMASSUSER]

Just got a Bolt EUV. I wanted to reopen the hypermiling topic by posting a suggestion and asking a question:

SUGGESTION: In my daily drive of about 10 miles round trip I put my Bolt in neutral in two areas where it seems safe to do so. One is a mile long section with a steady downhill grade, probably just 1 to 2 percent. On that section I accelerate to about 37 miles an hour and then I put the car in neutral. It travels about a mile and gradually decelerates to about 30mph. The other area is a half mile section right after the top of a steep hill, where I go into neutral before the top so the car slows to 20mph and then recovers to 35 on the way down.

It appears that for my five mile run I can get an efficiency boost of 10 to 15% by letting the car coast in these sections. So probably worth it.

QUESTION: When I am accelerating with the Bolt, does anyone know the efficiency curve of the motor? I mean, what is the sweet spot, in terms of the power generated per kilowatt?

In other words, when I want to accelerate from a stop sign to reach the speed needed for coasting, am I best off accelerating with 10kw, 20kw, 30kw, 40kw, etc.? My hunch is that I am better off accelerating with at least 20kW to maximize my time in neutral, but going all in with 50kW acceleration would be wasting energy by putting strain on the tires, etc.

I was trained as an electrical engineer, so I would love to find out the specs on the motor, or any details that the forum can provide. Thank you.

 

[XJ12]

I put my Bolt in neutral in two areas where it seems safe to do so

My understanding is the oil pump on the gear box doesn't run in neutral. Could be a bad thing I would think if the gears aren't getting proper lubrication.

 

[MichBolt]

Here's an efficiency map for the Bolt:

 

[MDVS]

Is there actually a neutral that disengages the motor from the drivetrain?
I thought that it was always engaged and that reverse and drive was changing the polarity of the motor and neutral turned off drive to the motor.

 

[Rmay635703]

Here's an efficiency map for the Bolt:

This matches my impericle experience, it’s hard to have too slow too gentle acceleration , the easier you are on acceleration and decelerating the better your efficiency.

other big one is hvac off.

 

[Packard V8]

I was trained as an electrical engineer, . . . It appears that for my five mile run I can get an efficiency boost of 10 to 15% by letting the car coast in these sections.

Your experiments and results do not correlate with mine and others. If one maintains those same speeds downhill in D or L, the car is effectively coasting. No electrical energy is being used and thus cannot be saved.

This matches my impericle experience, it’s hard to have too slow too gentle acceleration , the easier you are on acceleration and decelerating the better your efficiency.

Last century ICE hypermiling doesn't extend to this century's EVs. Been covered here a dozen times, both in theory and empirical tests but rate of acceleration has no bearing on efficiency. Floor it or featherfoot it up to the same cruise speed and the energy consumption is identical. Same with deceleration from cruise, the regeneration is the same, whether gathered slowly or rapidly.

The only circumstance where it makes any difference is in traffic, where one accelerates past a maintainable speed and then has to decelerate, when a slower, steadier, more efficient pace, without either accel or decel, could have been held.

jack vines

 

[Brad]

Instead of putting the car in neutral going down that hill, just feather the throttle until the kw display reads zero or close to zero. As for acceleration, 20kw or less. The motor is very efficient, but there are some losses in the battery, and I believe you can minimize this by accelerating slower.

 

[jefro]

Never put in neutral, unless you want a surprise.
Not only is it illegal but bolt might auto brake.
Put gas pedal to 0 kWH. I3 had detent to find.

 

[lynoise]

Put gas pedal to 0 kWH

I do agree with this statement
-but-
that is not true "freewheel" on the motor. It is generating some power to cover the car's needs (HVAC, lights, etc). Look at that reading while sitting at a red light, mine typically goes between 0.5kw to 2kw depending.

I have stated in other threads on this my opinion is that a little bit of regen is ideal when going down a long hill. You will travel the distance either way, anything you regen is just extra free power, unless you end up accelerating at the bottom because you slowed down too much... its an art.

 

[KyleBrightman]

I do agree with this statement
-but-
that is not true "freewheel" on the motor. It is generating some power to cover the car's needs (HVAC, lights, etc). Look at that reading while sitting at a red light, mine typically goes between 0.5kw to 2kw depending.

I have stated in other threads on this my opinion is that a little bit of regen is ideal when going down a long hill. You will travel the distance either way, anything you regen is just extra free power, unless you end up accelerating at the bottom because you slowed down too much... its an art.

I always maintain a 2-5kW output in downhill sections, this prevents any regen (which inherently has some losses) and has very slight mechanical acceleration to the wheels. I will build speed as I coast down the hill and I'll gently squeeze more into the throttle at the bottom of an incoming incline to transition back to cruise control within a harsh acceleration to maintain my original speed. It is probably imperceptible the amount of efficiency gained using this practice but I know converting kinetic energy of the car back into electrical energy in the battery has losses, so I try to minimize them when I'm in continuous motion (i.e. not approaching a light, stop sign, turn or traffic).

 

[Voldar]

When I had my Volt, the acceleration power used had to be around 20-23 kW to get the best range. I doubt there is a difference now in the Bolt EV.
GM did something smarter with the DIC in Enhanced mode : keep the acceleration/deceleration power between these lines and you are gold.

 

[Louis Chevrolet]

Here's an efficiency map for the Bolt:

What is the formula for converting torque (pu) and speed (pu) to kW?
For maximum acceleration it appears efficiency is dropping less than 10% from max, ignoring drivetrain losses which are minimal as long as tires haven't lost traction.
Perhaps motor generation efficiency sweet spot is low torque applied at about 50 mph. But the total efficiency of generation needs to consider air drag increasing with the square of velocity. So efficient operation should occur significantly below 50 mph.
The towing instructions in the owners manual should shed light on gearbox lubrication requirements in neutral when towed from the rear. Although a hardcore cheapskate would leave in drive with one pedal driving selected for the free battery charge with front wheels turning during towing.

 

[RMASSUSER]

Here's an efficiency map for the Bolt:

Thanks, do you know what the second Y axis means?

 

[MichBolt]

Thanks, do you know what the second Y axis means?

I believe it's just a color coding for efficiency at the boundaries of the graph where the contours would be difficult to show. Here's the source:

momen2016.pdf

Electrical Propulsion System Design of Chevrolet Bolt Battery Electric Vehicle Faizul Momen*, Khwaja Rahman, Senior Member IEEE, Yochan Son and Peter Savagian+ General Motors Global Propulsion System Pontiac, Michigan * [email protected] + retired from GM Abstract-A permanent magnet...

www.docdroid.net

 

[jefro]

0 is as close to zero as is safe.

I have a number of hills each day. One I slow to 45 then coast to 60 back up next hill to 50 and coast another mile all at 0 if I can.

 

[heogot]

Been covered here a dozen times

unfortunately it has been a Billion years since anybody wanted to Peruse through the archives of specialty forums for drawn out threads. Memories last Better when we engage in conversation Continuously. maybe you want to sit this one out and let the Kids Play in the Bathtub

 

[VoltoBolt]

Maybe the EUV is different than my 2019 Bolt EV, but at the express carwash, where I sit inside during the wash, when I push up to N, I sometimes get to R instead.

Of course at the beginning of the carwash I am standing still.

What happens where you are driving and you shift to R by mistake?!?

 

[EBS]

I don't dare to try, even on other ICE cars with automatic shift. But, in my manual transmission days, I can tell I couldn't shift it to R when the car is in forward motion.

 

[VoltoBolt]

So why does the OP dare to try it??

 

[tradosaurus]

Never thought I would be see a topic concerning an EV labeled "Hypermiling".
Best tips for range is to travel under 60 mph and pick a route where you have to brake often for regen.