ThudnBlundr
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Re: steep hill vehicle stall

Sun Dec 29, 2019 7:25 am

jaapv wrote:As to torque comparisons, if we do not take the weight of the car into consideration, they are meaningless.
The drawback of the PHEV or any other electrically driven car is that it has no facility to multiply torque by applying a low gear, which will remain the province of conventional vehicles. (unless somebody comes up with an electric Landcruiser sporting a low-gear box)
The Tesla Roadster had a gearbox, as does the new Porsche Taycan. In the latter case, it's only on the rear axle, while the front motor (if fitted) is a single-speed unit.
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greendwarf
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Re: steep hill vehicle stall

Sun Dec 29, 2019 4:00 pm

AlexBorro wrote: I didn't quite understand in your previous message what you mean by "it needs repeated kicks to turn on". Maybe you are confusion BLDC motors with another old kind of motors.
I don't think so Alex (although my education in electro mechanical principles is 50 years old). However, as I understand it the physics remains the same. There needs to be current switching (repeated kicks?) for rotation to continue. In a brushed motor the mass of the armature assists this in situations where rotation is being impeded, whereas the very advantage of the lack of mass in a modern brushless motor becomes a disadvantage in the described scenario due to lack of inertia.

AlexBorro
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Location: The Netherlands, south of Utrecht

Re: steep hill vehicle stall

Mon Dec 30, 2019 8:01 am

greendwarf wrote:There needs to be current switching (repeated kicks?) for rotation to continue. In a brushed motor the mass of the armature assists this in situations where rotation is being impeded
Now I think I understand your statement! What you said is completely true for brushed motors. In this type of motor, the rotating magnetic field is "controlled" by the mechanical brushes, that "switches" at fixed steps according to the rotational position. There will be positions where the angle between the rotating magnetic field and the fixed mag field will be low (= low torque) and other positions it will be high. If the motor happens to be stopped in the low torque position, there is no way to increase the torque without rotating the rotor a little bit (in order to commute to the next coil).

On the other side, in Brushless motors (BLDC) the rotating magnetic field is controlled by an electronic device (the inverter or speed controller) and this guy can place the rotating magnetic field anywhere. So if you are requesting full torque, the inverter knows (or can figure it out) the rotor position and will energize the coils in order to have such full torque. This is the reason we say a BLDC motor truly have full torque at 0 RPM (stopped).

I hope I could make it clear now!

Cheers.

Alex.

trevortron
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Re: steep hill vehicle stall

Wed Jan 29, 2020 4:02 am

jaapv wrote:The handbrake bit is superfluous, the car has a anti-roll-back feature, but I wonder a bit about your difficulties starting up a steepish hill. Did you engage 4 WD Lock, which distributes power equally between front and rear motor? It seems to be the same problem described above; the electric motor must be turning in order to build up power.
Sorry for the late reply, been busy with work & and other 'offline' activities.
I was aware of the anti-roll-back but didn't trust it enough to chance it with a 100ft drop just behind me! And yes, I did hit the 4WD button, it was the first thing I did.
Even with the momentum from having taken a run at it, it lost a lot of speed on the incline, just making it to the top and no more. No wheel-spinning though despite the loose terrain.

khayyam
Posts: 3
Joined: Sun Feb 21, 2021 1:23 pm

Re: steep hill vehicle stall

Sun Feb 21, 2021 1:31 pm

To resurrect a slightly old thread, we recently experienced in our new (to us) outlander phev. We have a very steep driveway, and the outlander stalled halfway up and wouldn't start again, just as OP described; had to go back and take a run at it. It's all good now, knowing how much speed to carry.

I do think it's a flaw in the series hybrid system, though. When stalled, the car is operating in EV only mode, and once stopped I couldn't figure out how to make it switch into series hybrid mode to get the extra power required. As I understand it, we should have 120 kw electric power from the motors (MY13, 60 front + 60 back), but the peak draw from the battery is only about 60 kw and anything more needs to come from the 70 kw generator on the ICE. But even with foot to the floor, at low speeds (and charge in the battery) it stays in EV mode, and 60 kw just isn't enough. Our other EV, which admittedly does have better power-to-weight, makes short work of the same hill - stop, start, go as slow as you like. Really that should be one of the perks of electric motors, with their flat torque curves.

AlexBorro
Posts: 33
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Location: The Netherlands, south of Utrecht

Re: steep hill vehicle stall

Tue Feb 23, 2021 1:44 am

khayyam wrote:
Sun Feb 21, 2021 1:31 pm
When stalled, the car is operating in EV only mode, and once stopped I couldn't figure out how to make it switch into series hybrid mode to get the extra power required. As I understand it, we should have 120 kw electric power from the motors (MY13, 60 front + 60 back), but the peak draw from the battery is only about 60 kw and anything more needs to come from the 70 kw generator on the ICE.
You are making a common mistake: confusing Power with Torque.
What matters in this situation is only the Torque - the force applied to the wheels. Indeed the power will be very very low, but the Torque will be the maximum and it is limited by the current output of the inverter and, of course, the maximum torque of the motors.

The Outlander has quite a good electric motors, I think the most powerful of all Hybrids I know. And it cannot use any help from the engine because it doesn't have a gearbox, instead a fixed gear ratio.

And as far as I know, almost all countries have regulation for the maximum inclination on public roads, and the Outlander can overcome it even with full load. All the vehicle's manufacturers apply these specifications to their cars. And If I'm not wrong, it is usually 12% for all public roads.
If for any reason you have a driveway outside these specs, then you know.. it is outside specifications!

greendwarf
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Re: steep hill vehicle stall

Tue Feb 23, 2021 2:42 am

This is the same problem as the PHEV's inability to drive over a brick from stationary - although it applies to all rotational machines with the energy input at the axle. Once it starts turning you get the benefit of angular momentum to keep it turning. Try riding a bike over a brick from stationary! What you need is an initial "jerk" to get it moving and the motors used in the PHEV have too low a moving mass to deliver that.

Once moving it will climb very steep slopes - there was a video from Japan showing it going up a 45 degree ramp.

nkane
Posts: 17
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Re: steep hill vehicle stall

Tue Feb 23, 2021 10:57 am

AlexBorro wrote:
Tue Feb 23, 2021 1:44 am

And as far as I know, almost all countries have regulation for the maximum inclination on public roads, and the Outlander can overcome it even with full load. All the vehicle's manufacturers apply these specifications to their cars. And If I'm not wrong, it is usually 12% for all public roads.
If for any reason you have a driveway outside these specs, then you know.. it is outside specifications!
Shhh! Don't tell CalTrans!!!

Old Priest Grade:https://www.dangerousroads.org/north-am ... -road.html
Highway 108 over Sonora Pass, 26%: https://en.wikipedia.org/wiki/Sonora_Pass

jaapv
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Re: steep hill vehicle stall

Tue Feb 23, 2021 6:08 pm

trevortron wrote:
Wed Dec 25, 2019 4:33 pm
I recently had a 'panic moment' on a steep incline. Not towing or anything, but (having previously owned a Tucson 4X4 which would go anywhere) I had reverse-parked down a fairly, but not excessively steep incline, thinking driving out would be a breeze. How wrong was I? When I tried to leave, I did the classic 'handbrake start' i.e. holding it on the handbrake to stop it rolling backwards further down the hill and releasing when ready to go. But would it go? Nope. All I could hear was the whine. I tried every option I could thinkof - 4WD lock, save & charge options to run the ICE but she wouldn't budge - and something started to smell a bit 'hot'. And this is when the panic set in. It was a remote location with no mobile phone coverage - that's why I was there, installing a TooWay satellite Internet system. So no chance of phoning for assistance, not that they'd have found me anyway!
Fortunately there was a bit more hill behind me which flattened out, round a corner & behind a shed. I nervously (because there was a near sheer drop to the other side) rolled back and took a run at it, got further up but it still stalled. It was third time lucky. After unloading maybe about 100kg of gear I took it right round the bend and floored it up the hill and just made it. (Then had to carry the gear up the hill)
Seriously, this did not feel like a 200HP car, the old '04 Tucson diesel (101HP) would have knocked spots off it!
Why did you use the handbrake? The car has automatic hill-holding.
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khayyam
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Joined: Sun Feb 21, 2021 1:23 pm

Re: steep hill vehicle stall

Tue Feb 23, 2021 8:19 pm

nkane wrote:
Tue Feb 23, 2021 10:57 am
AlexBorro wrote:
Tue Feb 23, 2021 1:44 am

And as far as I know, almost all countries have regulation for the maximum inclination on public roads, and the Outlander can overcome it even with full load. All the vehicle's manufacturers apply these specifications to their cars. And If I'm not wrong, it is usually 12% for all public roads.
If for any reason you have a driveway outside these specs, then you know.. it is outside specifications!
Shhh! Don't tell CalTrans!!!

Old Priest Grade:https://www.dangerousroads.org/north-am ... -road.html
Highway 108 over Sonora Pass, 26%: https://en.wikipedia.org/wiki/Sonora_Pass
Indeed. Avoid anything steep is not a great answer!

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