KERS!

[DangerousDoug]

I too have known people who drive like that - as you say, it's horrible to ride with them! I've no idea what actual difference it makes to consumption, but it feels very inefficient. Maybe an argument could be made for repeatedly running an ICE car in a more efficient higher power output mode, then backing off to coast. I can't imagine it would be good for an EV power train.

 

[smokie]

Do you mean nothing to be gained by KERS level 1 or KERS level 3? 1 being lower than 3?

 

[DangerousDoug]

Do you mean nothing to be gained by KERS level 1 or KERS level 3? 1 being lower than 3?

Sorry for the ambiguity in my previous post - yes, I mean no efficiency gain in KERS 1 (least regen). EV manufacturers provide configurable regen levels in order to be more acceptable to new drivers coming over from ICE. My brother, for instance, when driving my e-Niro for the first time found the (still relatively weak) regen level 3 to be unfamiliar and uncomfortable. When I dialled it back to ICE over-run levels (level 1) he was much more comfortable. I took to high regen almost immediately as I ride a motorcycle, which when dropping down the gears on the overrun can produce very strong engine braking, so I was used to it. Once you're used to high regen in an EV, you'd never go back, but there is a familiarisation period. Tesla simply don't bother, as the whole car is a learning curve, after which there's simply nothing better (I'd have one at the drop of a hat, if I could afford it ;-)).

 

[Count Zero]

I mostly drive in 3, but switch to 1 for long descents as this keeps the car rolling at a reasonable speed. Example last Sunday, decent from the Mam Ratigain pass at 390m to Glenelg at sea level, a distance of 5 and a half miles. Rolling at 30 to 40 mph. Gained 9 miles range (at least according to the GOM). Single track road, passed one tractor plus a couple of cars on the way up using the passing places.

 

[DangerousDoug]

I mostly drive in 3, but switch to 1 for long descents as this keeps the car rolling at a reasonable speed. Example last Sunday, decent from the Mam Ratigain pass at 390m to Glenelg at sea level, a distance of 5 and a half miles. Rolling at 30 to 40 mph. Gained 9 miles range (at least according to the GOM). Single track road, passed one tractor plus a couple of cars on the way up using the passing places.

Sounds like a lovely place to take the motorbike! ;-)

 

[RoadUser]

Isn't KERS1 more efficient, not due to the regen, but it slows the car down in a more predictable manner, especially when no one is behind, so not needing to press the throttle again to keep up.

On a slightly different note, what's that motorize type noise when applying the breaks sometimes, is that rear brake pads being applied? As the noise if similar to when releasing the hand break. Does the front breaks have a similar setup or a more traditional one? Thanks

 

[DangerousDoug]

Isn't KERS1 more efficient, not due to the regen, but it slows the car down in a more predictable manner, especially when no one is behind, so not needing to press the throttle again to keep up.

On a slightly different note, what's that motorize type noise when applying the breaks sometimes, is that rear brake pads being applied? As the noise if similar to when releasing the hand break. Does the front breaks have a similar setup or a more traditional one? Thanks

Hi RoadUser, welcome - The point of regen is it recovers the kinetic (motion) energy that's been put into the car, and converts it back into electricity, storing it back in the battery. Electric motors are also generators (you can use the alternator from your old ICE car as a motor, just by putting a 12v battery across it). Hybrid cars use this mechanism to improve fuel efficiency by recovering motion energy, rather than simply heating up the brakes (that's about the ONLY advantage of a petrol hybrid!). So the more energy you can recover, the more efficient your journey becomes. You can vary the amount of regen by raising your foot more gradually off the accellerator (just like pushing the brake pedal more or less firmly to vary the amount of braking). The motor is run "in reverse", generating electricity from the car's motion, reducing that motion while generating electricity. The more you can recover like this, the less you need to use the friction brakes, so the less motion energy you lose in heat in the brakes. Whenever you use the brakes, you're throwing away energy you paid for (either electricity in the case of EV, or fuel in the case of ICE). Cars with "true" one pedal driving tend to see their brakes lasting a very long time (Teslas often don't replace brake pads for over 100,000 miles if driven right). This is why you want the strongest possible regen, so you have the most potential braking power under your accellerator foot. You don't use that power all the time (in the same way you don't do an emergency stop every time you use the brakes) - you develop a light foot, to control the power you have.
As for your braking noise, I'm not sure I understand what you mean. But one of the issues with EVs is that because the brakes are used so rarely, they can tend to rust up, so they can be a bit more noisy than equivalent ICE cars. EV brakes are the same as ICE in construction etc., so there's no difference mechanically.

 

[johnb80]

Hi RoadUser, welcome - The point of regen is it recovers the kinetic (motion) energy that's been put into the car, and converts it back into electricity, storing it back in the battery. Electric motors are also generators (you can use the alternator from your old ICE car as a motor, just by putting a 12v battery across it).

No you cant.

Hybrid cars use this mechanism to improve fuel efficiency by recovering motion energy, rather than simply heating up the brakes (that's about the ONLY advantage of a petrol hybrid!). So the more energy you can recover, the more efficient your journey becomes. You can vary the amount of regen by raising your foot more gradually off the accellerator (just like pushing the brake pedal more or less firmly to vary the amount of braking).

Agreed

The motor is run "in reverse", generating electricity from the car's motion, reducing that motion while generating electricity.

If you mean spinning the motor the other way, sorry youre wrong.

The more you can recover like this, the less you need to use the friction brakes, so the less motion energy you lose in heat in the brakes. Whenever you use the brakes, you're throwing away energy you paid for (either electricity in the case of EV, or fuel in the case of ICE).

Correct

Cars with "true" one pedal driving tend to see their brakes lasting a very long time (Teslas often don't replace brake pads for over 100,000 miles if driven right). This is why you want the strongest possible regen, so you have the most potential braking power under your accellerator foot. You don't use that power all the time (in the same way you don't do an emergency stop every time you use the brakes) - you develop a light foot, to control the power you have.

Great explanation, my BMW i3 has 85,000 miles on the original disks and pads, still not showing any signs of wear.

As for your braking noise, I'm not sure I understand what you mean. But one of the issues with EVs is that because the brakes are used so rarely, they can tend to rust up, so they can be a bit more noisy than equivalent ICE cars. EV brakes are the same as ICE in construction etc., so there's no difference mechanically.

Whilst that can occur, the pads are still resting gently against the discs so rusting shouldnt be an issue.

 

[DangerousDoug]

I seem to have caused some misunderstanding in my (rather long) post above. When I say "in reverse" I don't mean the motor runs backwards - I mean the electricity current flow is in reverse, generating current rather than consuming it. Of course the motor still spins in the same direction!
As for using an alternator as a motor - you're right, it's more complicated than that, for modern 3phase alternators - I was thinking of old dynamos (not impossible, though )

 

[maskull]

I can confirm that the brake pads last a long time on my 2 previous hybrids . The downside is that the brake discs tend to rust . My first hybrid had to have the discs replaced at 50000 miles , the downside of regeneration . Swings and roundabouts . So possibly it's best to perform an emergency stop , on a safe quiet piece of road of course , to clear rust off the discs . I should imagine the same would apply to an EV

 

[Gomev]

Hi RoadUser, welcome - The point of regen is it recovers the kinetic (motion) energy that's been put into the car, and converts it back into electricity, storing it back in the battery. Electric motors are also generators (you can use the alternator from your old ICE car as a motor, just by putting a 12v battery across it). Hybrid cars use this mechanism to improve fuel efficiency by recovering motion energy, rather than simply heating up the brakes (that's about the ONLY advantage of a petrol hybrid!). So the more energy you can recover, the more efficient your journey becomes. You can vary the amount of regen by raising your foot more gradually off the accellerator (just like pushing the brake pedal more or less firmly to vary the amount of braking). The motor is run "in reverse", generating electricity from the car's motion, reducing that motion while generating electricity. The more you can recover like this, the less you need to use the friction brakes, so the less motion energy you lose in heat in the brakes. Whenever you use the brakes, you're throwing away energy you paid for (either electricity in the case of EV, or fuel in the case of ICE). Cars with "true" one pedal driving tend to see their brakes lasting a very long time (Teslas often don't replace brake pads for over 100,000 miles if driven right). This is why you want the strongest possible regen, so you have the most potential braking power under your accellerator foot. You don't use that power all the time (in the same way you don't do an emergency stop every time you use the brakes) - you develop a light foot, to control the power you have.
As for your braking noise, I'm not sure I understand what you mean. But one of the issues with EVs is that because the brakes are used so rarely, they can tend to rust up, so they can be a bit more noisy than equivalent ICE cars. EV brakes are the same as ICE in construction etc., so there's no difference mechanically.

You appear to be neglecting the effect of slowing and accelerating. When using max regen on fast roads the energy used to regain speed is more than the energy recovered in slowing down, so the weakest regen, and anticipation of the road ahead produces the best results.

 

[DangerousDoug]

You appear to be neglecting the effect of slowing and accelerating. When using max regen on fast roads the energy used to regain speed is more than the energy recovered in slowing down, so the weakest regen, and anticipation of the road ahead produces the best results.

I'm afraid I can't agree, Gomev. Anticipating the road ahead certainly produces the smoothest and most efficient driving style, but again, you only slow down when you need to, and to the extent you need to. Lower regen just means you don't have as much control over decelleration, so you'll need to use the (wasteful) brakes more. In highest regen setting you can still slow down gradually - again it's all down to that light right foot.

 

[Gomev]

I'm afraid I can't agree, Gomev. Anticipating the road ahead certainly produces the smoothest and most efficient driving style, but again, you only slow down when you need to, and to the extent you need to. Lower regen just means you don't have as much control over decelleration, so you'll need to use the (wasteful) brakes more. In highest regen setting you can still slow down gradually - again it's all down to that light right foot.

I wasn't anticipating that you would agree your sole mantra has been max regen, max regen and light foot. I don't think anybody would dispute the latter. Others have differing ways to achieve efficiency without using max regen setting ALL the time. Your method may be the best and the only way to achieve the best, but unlikely.

 

[maskull]

I'm afraid I can't agree, Gomev. Anticipating the road ahead certainly produces the smoothest and most efficient driving style, but again, you only slow down when you need to, and to the extent you need to. Lower regen just means you don't have as much control over decelleration, so you'll need to use the (wasteful) brakes more. In highest regen setting you can still slow down gradually - again it's all down to that light right foot.

I personally find KERS 1 the best when coasting to an anticipated stop , KERS 3 is far too aggressive for my taste

 

[smokie]

My first hybrid had to have the discs replaced at 50000 miles , .... So possibly it's best to perform an emergency stop , on a safe quiet piece of road of course , to clear rust off the discs . I should imagine the same would apply to an EV

Same here on the Ampera, rear brake seizure at about 50k miles due to rusting due to lack of use.

The recommendation from the knowledgeable ones on the forum was to knock it into neutral when doing the "emergency" braking, to make sure the energy all went through the discs and KERS didn't steal any of it.

I've mentioned this before here without having tested whether it's do-able on the MG but I've subsequently checked and it is.

 

[DangerousDoug]

I wasn't anticipating that you would agree your sole mantra has been max regen, max regen and light foot. I don't think anybody would dispute the latter. Others have differing ways to achieve efficiency without using max regen setting ALL the time. Your method may be the best and the only way to achieve the best, but unlikely.

HaHa - vive la difference, Gomev. I think we agree on many more things than we disagree - we're both on an EV forum for one thing The great thing about the car market over the last 50 years or more is the huge variety and multitude of companies, models etc (compare with mobile phone operating systems) so whatever driving style gives one the most enjoyment and utility is the one you should stick with .

 

[smokie]

Android all the way LOL

 

[johnb80]

I seem to have caused some misunderstanding in my (rather long) post above. When I say "in reverse" I don't mean the motor runs backwards - I mean the electricity current flow is in reverse, generating current rather than consuming it. Of course the motor still spins in the same direction!
As for using an alternator as a motor - you're right, it's more complicated than that, for modern 3phase alternators - I was thinking of old dynamos (not impossible, though )

Dynamo's were easy to use as a motor and could be used as a parallel or series motor. Series would give low speed / high torque and high speed \ low torque. I have done it many times in my younger years.
Alternators can be operated with a brushless speed controller with a DC supply onto the slip rings.

 

[Spaniard]

I'm afraid I can't agree, Gomev. Anticipating the road ahead certainly produces the smoothest and most efficient driving style, but again, you only slow down when you need to, and to the extent you need to. Lower regen just means you don't have as much control over decelleration, so you'll need to use the (wasteful) brakes more. In highest regen setting you can still slow down gradually - again it's all down to that light right foot.

Do you really think that every time you touch the brake pedal, the brake pads actuate over the disks?
I think you are not aware that pads do not actuate until you require a deceleration higher than the energy that the kers can absorb... and you can feel it (if a experienced driver).

This is: it leads to exactly the same amount of energy recovered releasing the gas pedal at regen 3 than slightly pressing the brake pedal at regen 1 to obtain a -24% power.

In other words, the only advantage of regen3 is making you aware of how much energy the car can absorb to decelerate before it needs to press the brake pads, but if you have a good precise touch on the brake, you may obtain the same regen... it is just a muscle precission exercise: precission releasing the pedal (barely ever exercised in an ICE car), or precission pressing the brake (exercised in aggresive driving - not usual but still some have done it previously).

 

[Kompins]

After a period of faffing about with various settings in the first couple of months ownership I came to the conclusion that nothing seemed to make much difference so always drive in the default settings with a feather like foot and virtually never use the brakes. I just enjoy driving the 5 and get excellent efficiency and range.