B-mode for regular driving

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benswing

Well-known member
Joined
Feb 5, 2013
Messages
47
Location
Montclair, NJ
Apparently some people have been informed to not use B-mode as their regular driving mode.

As an experienced driver of electric vehicles I have always used the regenerative braking as my primary means of slowing down and no other manufacturer (to my knowledge) has warned against doing this. I have only used the B-mode to drive so far and plan to continue using it, but if there is a compelling reason not to use it, then I want to know.

Any technical information is especially welcome.

Post inspired by this quote from another thread:
rdct said:
Regarding the "B" mode; does anyone have reliable info to confirm that it is safe to drive constantly in it?

I'm not discounting it either way as I haven't read anything from Mitsubishi on it, however my salesman was the only "qualified" person at the dealership on the MiEV, and after asking the same question, he informed me that he was told not to drive around in it.

He did admit that he wasn't given a technical explanation why when I asked because like a kid I need to know why and it needs to make sense or I'm likely going to do it anyway :D
 
Lots of us drive around using just the B mode and have experienced no problems whatsoever. It simply means full power and a lot of regen. Also, I don't recall anything in the manual about not doing so and I read the manual cover to cover several times.

The hypermilers will comment on using coasting in favor of regen where possible and that is a good practice to extend your range.
 
Euro clones, Peugeot iOn and Citroen C-Zero, have only one forward speed, "D", and I think is similar at iMiev's "B", with a lot of regen.
 
I think it's largely a matter of personal preference. Both E and B facilitate "one pedal" driving, but which works better for you depends on your driving style and the traffic conditions you most often face. In addition to the long steep downhills for which B is theoretically intended, I could see B being particularly useful in congested freeway stop and go, where it's useful to accelerate quickly but also to slow down often, and often in quick succession.

I would say that regardless of driving mode, one should bear in mind that either flooring the accelerator or going for max regen from high speed will slam the battery, albeit in different directions. Max regen, remember, hits the battery with a surge far greater than L2 charging. On the theory that every little bit counts, I'd say that driving in B, while not inherently "bad", does require a deft touch on the accelerator to avoid extremes and so reduce wear on the main battery. Basically, the closer you come to experiencing a jerky "first day driving a golf cart" feel, the worse it is. I think that's easier to avoid in E, which is a mode designed to facilitate the most efficient and least damaging behavior.

That said, E is definitely a convenience, not a technical necessity, and equivalent behavior can be achieved in either B or D with judicious use of accelerator and brake. E, on the other hand, cannot match the smooth power of D or B, offering fairly muted "throttle" response unless you "floor" it to get full emergency acceleration.

Bottom line: drive in whatever mode best suits you and your circumstances. But ideally, the driving style that best preserves range and longevity will have the vehicle behave as if it's in E, regardless of the selected mode.
 
MLucas said:
Lots of us drive around using just the B mode and have experienced no problems whatsoever. It simply means full power and a lot of regen. Also, I don't recall anything in the manual about not doing so and I read the manual cover to cover several times.

The hypermilers will comment on using coasting in favor of regen where possible and that is a good practice to extend your range.
I also use the B mode 100% of the time - You can even 'coast' while in B mode . . . . there is a throttle position where the motor is neither being driven by the battery, nor regenerating power to the battery - It's effectively the same thing as shifting to 'N' except you don't need to bother moving the stick

Don
 
Don't want to split hairs, but since a few of us have mentioned using the go-pedal to modulate the regen, it's probably worth noting that the power meter measures net power flows, not just power used by the drive train. This makes a real difference for winter driving with the energy vampire heater on. If you put the car in neutral, you will actually see a slight net power draw because of the heater. Consequently, if you then go to D and press on the pedal until the meter says you're "energy neutral" moving down the road, you're actually e-braking and slowing down, with regen capturing enough power to offset the heater's draw, not really free-wheel coasting. I haven't figured out a good fix for this - perhaps just give up on the meter and pay attention to how I'm moving!
 
Vike said:
I haven't figured out a good fix for this - perhaps just give up on the meter and pay attention to how I'm moving!
True enough ;)

I don't really look at the meter much when driving - Sometimes going down hill you actually want to maintain a steady speed which could mean using a little bit of juice (shallow hill) or a little regenerative braking (steeper hill) so I usually just concentrate on keeping the speed I want

I consider all this a plus vs shifting into neutral where you have no control over your speed . . . . unless you friction brake or shift back into gear so you can add a little speed. Modulating the pedal in B is so much easier to do and more efficient too, plus once you've mastered it, it's all second nature

I really wish B was the first selection after neutral . . . . or, that they had given us the opportunity to designate the drive modes any way we liked

Don
 
Don said:
I really wish B was the first selection after neutral . . . . or, that they had given us the opportunity to designate the drive modes any way we liked
Most of all I'd like a drive mode with zero regen on "coast" - if D behaved that way, I'd probably use it more often. I think a case could be made for having E behave that way, really - so D would be "normal" (i.e., most ICE-like behavior, with full power and mild regen-induced deceleration similar to engine braking), E would be truly maximum efficiency (including regen-free coasting), and B would be downhill and/or one pedal "golf cart" mode (intended as descriptive, not a knock - I do use it myself, after all ;) ). I hate being in N (so almost never do it), and it's a pain to feather the accelerator to achieve true coasting, which I think is key to maximizing range. Regen after all is only a brake pedal away.
 
Fascinating discussion. After seven months of ownership, I have settled on E as my "default" preference. I guess what I don't like about B is that I slow down too quickly, and cars behind me get "bigger" in the rear view mirror. My two cents worth.
 
benswing said:
Apparently some people have been informed to not use B-mode as their regular driving mode.

As an experienced driver of electric vehicles I have always used the regenerative braking as my primary means of slowing down and no other manufacturer (to my knowledge) has warned against doing this. I have only used the B-mode to drive so far and plan to continue using it, but if there is a compelling reason not to use it, then I want to know.

Any technical information is especially welcome.

Post inspired by this quote from another thread:
rdct said:
Regarding the "B" mode; does anyone have reliable info to confirm that it is safe to drive constantly in it?

I'm not discounting it either way as I haven't read anything from Mitsubishi on it, however my salesman was the only "qualified" person at the dealership on the MiEV, and after asking the same question, he informed me that he was told not to drive around in it.

He did admit that he wasn't given a technical explanation why when I asked because like a kid I need to know why and it needs to make sense or I'm likely going to do it anyway :D
I was surprised to see this in the Ford Focus Electric owners manual, page 264;

SINGLE SPEED AUTOMATIC TRANSMISSION

L (Low)
• Provides maximum motor braking.
Is not intended for use under extended or normal driving conditions and results in less miles per charge.
• The transmission may be shifted into L (Low) at any vehicle speed.
 
Hi All,


I used to hypermile my old Manual Civic as much as I could when I was not in a hurry and the traffic would allow it. Basically I would use the
pulse and glide technique and the "Drive like you have no brakes" method of controlling speed and timing lights and traffic up ahead. So I was used to this
way of driving before we got our iMiev. When I started driving the iMiev I found the regen was something that I had to get used to. I found that the B mode worked best for sporty type driving. Brisk accel and then decel into turn and then back on the power. More of a fun type of driving with an additional advantage of the strong regen charging the battery. In the beginning I did kind of miss not having a coast mode but I quickly found that the easiest way to coast was to put the car in neutral which was the same technique I used on the Civic.

I like E mode because it give you a finer control of power application and encourages you to use less power and accelerate slower. This works well when you are more alone on the road and not in a hurry to get up to speed. I also like B mode to get the strong regen when you need to slow down rapidly. I think my ideal hypermiling driving scenario is to accel gently from a stop in E mode, then switch to D mode to maintain speed and switch between D and neutral to coast/maintain speed then gently regen in D then E then B depending on the distance to the stop using the brake pedal only at the end to stop the car.
You do have to be careful in D mode because it's much easier to apply too much power, D mode and N and right beside each other so that works best but I sometime think it would be nice to have a button on the top of the shifter (like the old James Bond ejector seat button) that would allow you to jump from E mode to N to allow you to coast without using the shifter. Another "Hypermiler special" project to add to the iMiev one day.


So when I drive this way I am basically all over the place and I'm practically shifting like i used to do in the civic.

But traffic being what it is, practically I spend most of my time in B and E Starting off in B or E to get a gentle start and then modulating the speed with E most of the time and braking in B. I have also found that when I'm driving in E and I need to accelerate quicker instead of pressing the pedal down I switch to D and just hold the pedal at it's current position. It's kind of like a "turbo" mode like the old 386's, then when I'm up to speed I switch back to E to maintain speed all of this without changing the go pedal position.

Maybe after driving a manual transmission for so long I feel I still need to shift or maybe its just me trying to be as efficient as I can just for fun but I find that those are the techniques I use most often with the iMiev.


On another note temps are on the rise over here. The deep freeze seems to be over, range is up and spring is just around the corner iMiev life is good..... :D


Don.......
 
Kei Jidosha said:
I was surprised to see this in the Ford Focus Electric owners manual, page 264;

SINGLE SPEED AUTOMATIC TRANSMISSION

L (Low)
• Provides maximum motor braking.
Is not intended for use under extended or normal driving conditions and results in less miles per charge.
• The transmission may be shifted into L (Low) at any vehicle speed.
If the transmission only has a single speed, how do you 'shift' it at all :lol:

I'm sure their warning about getting less miles per charge in the regenerative mode is very accurate . . . . for some people

Many drivers who grew up only driving auto trans equipped ICE vehicles have a terrible habit that they are not even aware of - I've seen it hundreds of times riding with many drivers, and thousands of times following them on the road. Their 'normal' mode of driving is to gently press the accelerator until they realize they are actually going a little faster than they want to go and then release the pedal just a touch until they realize they are going a little slower than they want to go and then . . . . repeat. If you're in the car with them, you can see this behavior firsthand by keeping an eye on the speedometer and watching their foot on the accelerator. If you're driving behind them, you'll quickly find your cruise control is of no use - They go mile after mile at a speed somewhere between 5 miles over and 5 miles under the posted limit. Why those sorts of driver seldom use the cruise control is a mystery, but most of them don't

Driving an EV with regenerative braking this way will cost you range because the car doesn't coast like an auto trans equipped ICE does when you release the pedal - Even in the ICE, they are getting less than optimal mileage, because this isn't an efficient way to drive, but in an EV with regenerative braking, it's terrible. I'm guessing this is why most EV's either don't have regenerative braking, or have a way of limiting it . . . . the 'D' selection on the 'shifter'

You *can* drive an iMiEV constantly in the 'B' mode and get between 70 and 80 miles of range . . . . I've been doing it for nearly a year

I'm sure this makes sense to everyone . . . . I'm also sure none of you *think* you ever drive this way, but if you seldom drive manual transmission ICE vehicles, I'd be willing to bet that it applies to many (if not most) of you and you just don't realize it. Manual transmission cars engine brake when the pedal is released . . . . they do not coast like auto transmission cars do, so this isn't a habit most of those drivers ever get into

So . . . . unless you're concentrating on keeping a steady speed, the 'B' mode on our cars is probably not for you, as it will cost you range

Don
 
For best mileage results, one should drive as if they have no brakes...of any kind.

Of course, you can't always do this due to traffic, time, unforeseen road obstacles...
 
Hi Don,

Re shifting into N for coasting. I also find it being much more efficient that trying to stay right in neutral zone with the econ mode arrow (between regen and Eco).

However, I have not done it often because worried to damage the mechanism. My thinking was that if our gearbox is in fact a single one and there is a direct connection to the engine, then when going from N into D while car is moving would cause a friction because the engine will have to go from zero to several thousand rev/ min without a proper clutch mechanism.

Do you think I am being too cautious ?

Thanks
 
Hello Llecentaur et all,

I remember reading somewhere in this forum that the transmission is always coupled to the motor so presumably the motor is always spinning when the car is in motion. If this is so putting it in N just decouples things electrically. Same thing for R it's just an electrical reverse mode the motor spins in reverse.

Anyone know if this is the case or not ?

If true then I don't see a problem with coasting in N.

Don....
 
You're right, Don. Citroen and Peugeot clones don't have B and ECO mode. Only P,D,N,R modes. So the only way to coast is N for these cars. N is natural mode for coasting in all automatic gears I think.
 
Zelenec said:
So the only way to coast is N for these cars. N is natural mode for coasting in all automatic gears I think.
N is one way to coast, but you can coast just as efficiently by positioning the accelerator so that no electrical current is flowing in or out of the motor when the transmission is in any driving mode. This is exactly what N does.

Unlike in ICE car transmissions, N does not shift the transmission out of gear but merely disconnects the battery pack from the motor. So shifting from N to D or any other driving mode does not suddenly cause the motor's rotational speed to change from 0 to something fast as it would in an ICE car. When your car is not moving and is in N, pressing the accelerator does not cause the motor to spin (you would be able to hear or feel something if it did). Shifting from N to any drive mode might suddenly cause electrical current to flow in or out of the motor, but I'm guessing that the motor controller would only gradually increase the electrical current to avoid any sudden jerky acceleration or deceleration.
 
I have done many tests and can confirm that rolling down a gentle slope is clearly more efficient in N than trying to stay in neutral zone while in D.

I can not explain why, other that there is some spinning in the engine, maybe some resistance to the cooling liquid ? Not really qualified nor have the data to conclude.

On the other hand, it is true that switching from N to D say at 50km/h does not make any noise or bump which might mean that the engine is really coupled at all times as Don suggested.

If this is the case, why is there such a difference between freewheeling in N and "freewheeling" in D with Econ arrow in neutral zone ?

Maybe those with the original iMiev can help by answering this question: does the car freewheel more efficiently in E than in D or even B ?

If so, then Don's idea that in D we have an electrical coupling would be verified...

Thanks
 
DonDakin said:
I remember reading somewhere in this forum that the transmission is always coupled to the motor so presumably the motor is always spinning when the car is in motion. If this is so putting it in N just decouples things electrically. Same thing for R it's just an electrical reverse mode the motor spins in reverse.
Don is correct. The various driving modes are just electronically switched. The only mechanical connection between the shifter and the transmission is to engage the Park pawl to lock the transmission. Shifting between Neutral and Drive can be done at any speed and under acceleration or deceleration because mechanically nothing changes - The drive motor and the wheels are always connected, so the 'shift' does nothing mechanically

If you're 'coasting' downhill in any driving mode with the needle between the regen and the green Eco zone, you're doing the same thing as shifting into neutral - Consuming zero energy . . . . plus you have immediate access to both accelerate or regenerative brake if needed

Don
 
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