starting, stopping and reversing
Discussion
I'm really not sure on this one, I feel I should know but for some reason I can't make up my mind...
I have recently made the move to an EV (BMW I3) and have found myself increasingly doing the following:
- Pressing the on button and then just going for it, no warm up or mechanical sympathy really.
- Making full use of the one pedal driving. Not a problem until I was sat on a gradient in traffic having come to a stop and just let the car in drive hold itself on the hill without rolling backwards not putting my foot on the brake.
- either reversing or driving forward and not coming to a complete stop before altering the direction of drive (very very low speed)
Now I never used to do this in an ICE car as I knew that it was bad for the car. However EV, less moving oily bits, no clutch and no gearbox... I don't have the same clarity as before although it doesn't feel right I have trouble saying to myself why it isn't right.
Anyone with more brains than me know whether these little habits that are forming if they are OK or bad to the longevity of the car?
I have recently made the move to an EV (BMW I3) and have found myself increasingly doing the following:
- Pressing the on button and then just going for it, no warm up or mechanical sympathy really.
- Making full use of the one pedal driving. Not a problem until I was sat on a gradient in traffic having come to a stop and just let the car in drive hold itself on the hill without rolling backwards not putting my foot on the brake.
- either reversing or driving forward and not coming to a complete stop before altering the direction of drive (very very low speed)
Now I never used to do this in an ICE car as I knew that it was bad for the car. However EV, less moving oily bits, no clutch and no gearbox... I don't have the same clarity as before although it doesn't feel right I have trouble saying to myself why it isn't right.
Anyone with more brains than me know whether these little habits that are forming if they are OK or bad to the longevity of the car?
I think you'd struggle to significantly damage a modern ICE car let alone an EV by doing any of those things; the ECU will either point blank refuse to let you or the mechanical bits will have been engineered to cope.
From the point of view of what you might wear faster... an EV still has a gearbox with oil in it (even if it's a single speed) which presumably will alter viscosity with temperature. There's not much else really.
From the point of view of what you might wear faster... an EV still has a gearbox with oil in it (even if it's a single speed) which presumably will alter viscosity with temperature. There's not much else really.
kambites said:
I think you'd struggle to significantly damage a modern ICE car let alone an EV by doing any of those things; the ECU will either point blank refuse to let you or the mechanical bits will have been engineered to cope.
From the point of view of what you might wear faster... an EV still has a gearbox with oil in it (even if it's a single speed) which presumably will alter viscosity with temperature. There's not much else really.
I would say similar, and add that part of the ‘warm up’ is attuning yourself to driving - observation, and scanning forward and laterally, using mirrors, is different to just when you walk about indoors!From the point of view of what you might wear faster... an EV still has a gearbox with oil in it (even if it's a single speed) which presumably will alter viscosity with temperature. There's not much else really.
You can't over torque the motor by switching from forward to reverse. If the car is rolling backwards and you have selected drive and stamp on the the throttle the torque applied will stop you moving backwards and start you moving forwards very quickly, but it will not exceed the torque the entire powertrain is designed for, because the maximum torque the motor can produce is controlled electronically.
It's hard to explain but you can't apply more twisting force to the drive shafts etc just because of the rapid change of direction. The overall twisting maximum force - torque - they have to handle will be the same as if the car was launched full throttle from standing.
So.. don't worry about it.
It's hard to explain but you can't apply more twisting force to the drive shafts etc just because of the rapid change of direction. The overall twisting maximum force - torque - they have to handle will be the same as if the car was launched full throttle from standing.
So.. don't worry about it.
Pica-Pica said:
I would say similar, and add that part of the ‘warm up’ is attuning yourself to driving - observation, and scanning forward and laterally, using mirrors, is different to just when you walk about indoors!
I take your point on the "warm up", just to be clear I'm not randomly jumping in the car outside of a school at kicking out time and planting the accelerator... More of an observation that when I get in my MX-5 I drive for a good 10 mins without taking the revs up to get everything nice and warm, with the EV I just get going.Nice to hear I am not being daft, I have always looked after my cars and I continue to do so it was just I noticed I was picking up some habits I'd not had before and wanted to check.
Moonpie21 said:
- Pressing the on button and then just going for it, no warm up or mechanical sympathy really.
Anyone with more brains than me know whether these little habits that are forming if they are OK or bad to the longevity of the car?
Your tyres still need to warm up potentially, which is worth considering Anyone with more brains than me know whether these little habits that are forming if they are OK or bad to the longevity of the car?
As pretty much every aspect of the drive is software controlled I wouldn't expect the software would let you do anything harmful to the car, so unless driving at 100% all the time (in which case the usual mechanical issues will probably be a greater concern) I don't think you need worry.
Hanging on the motor while stopped on a steep gradient is presumably passing some significant current through a stalled motor? or does the car know better and put the brakes on?
40 years ago I had some experience of driving an electric fork lift, where using the back pedal to slow the machine was effective but wasteful, and occasionally resulted in shooting backwards at a rate of knots instead of merely stopping!
Happy Days!
40 years ago I had some experience of driving an electric fork lift, where using the back pedal to slow the machine was effective but wasteful, and occasionally resulted in shooting backwards at a rate of knots instead of merely stopping!
Happy Days!
pills said:
Dumb question alert - how long does it take to warm up the gearbox oil on an electric car?
I was told by a Nissan EV engineer that it's not oil (as no gears) but really an ATF, and that because there's no range of cogs and teeth etc that the demands on it are fairly benign. Hence not really needing to warm up to become effective. Also why, I think, the service intervals are gigantic on it.OutInTheShed said:
Hanging on the motor while stopped on a steep gradient is presumably passing some significant current through a stalled motor? or does the car know better and put the brakes on?
Hill hold is calibrated specifically to include thermal limits of the inverter and motor.And motor looses scale with motor power, and at zero speed, a massive amount of torque is really no power at all (because the motor isn't spinning there is no back emf being generated, so all the inverter needs to apply to drive a positive current into the phase windings is to overcome the dc resistance of those windings which is absolutely tiny, milliohm level, which of course is why an electric motor, being almost entirely impedance rather than resistance, is also incredibly efficient, clearly.
Take a typical eMachine for a BEV, which has a torque characteristic of say 2Amps per Nm, and a dc phase resistance of 1mO. Say it takes 50Nm machine torque to hold the car on a hill, that's 100 amps (2 A/Nm x 50 Nm = 100) and 0.1 volts (100 amps x 0.001ohms = 0.1volts) which multiplied together means just 10 watts of power being dissipated in the motor! A typical BEV motor at peak power these days has say at least 150,000 watts of power by comparison.
The I3 like all BEVs also simply won't let you "change gear" from forward into reverse (no actual gears are changed clearly) when moving that fast or without your foot on the brake etc.
I daily thrash the crap out of my i3s and did so with my previous i3 for 6 years and no issues at all. It's one of the best things about it, get in, floor it, job done :-)
Gassing Station | EV and Alternative Fuels | Top of Page | What's New | My Stuff