The combo of using electricity around town day to day with the option of long range gas based road trips appeals to me. I am roughly 200-250 miles from Lake Tahoe and even if I wanted a Tesla I would not count in that range for that type of trip, although many do so. So plug in for around town and hybrid for the mountains. But some of the offerings like RAV4, Lexus, and Volvo all have a dedicated electric motor driving two of the four wheels. If I am chugging up the mountains running on both gas and electricity I would expect to run the risk of depleting the battery. Would that mean 2WD at the point where I really need 4WD? One review of a Hyundai PHEV AWD (I forget which) mentioned that the electric motor is connected to the engine and therefore all driven wheels at all times. Anyone have experience with how this works in the real world of cold temperatures and climbing altitude?
Javelin
MegaDork
3/20/22 12:23 p.m.
Each one is built differently, so it's going to depend. Our Q5 e has the electric motor in between the engine and trans, so we never lose AWD. When the battery hits 0 the ICE turns on seamlessly.
Generally, you will not run the system at WOT terribly long, so the ICE has enough power to drive their wheels and the other set of tires via electrical power.
Not AWD, but our Chev Volt has a mountain mode setting that reserves 20% of the battery capacity for a power boost on long grades, which is replenished when demand is less. I imagine most manufacturers would do something similar. Also, even when not in mountain mode, when the battery is "empty" the car can pull from the battery when needed, since the battery never is allowed to go completely dead. Be aware that most hybrid AWD systems are not continuous AWD, but rather only kick in the rear electric motor as needed, just like the ICE AWD systems like Subaru and Toyota use, among others.
The larger concern if you are going down a mountain and the battery is full. You usually can not get engine braking with a hybrid.
IIRC this and the reverse issue (it is 100% electric) is why Escape hybrids are not rated to tow much.
In reply to Turboeric :
The interesting thing is that a lot of Toyota AWD systems bother to package a center differential in the transverse setup. Learned that the fun way after I removed the driveshaft from a Highlander on a drive-on lift. Oops, we no longer have Park!
A large percentage of Subarus have a center diff, with either a viscous limited slip or a computer controlled electronic one. At least with the 4EATs, the turbo models had a center differential and the non turbo models were FWD-with-clutch-to-rear but I am sure there are exceptions. 99% sure that all manual transmissions without a 4wd lever/button have a center diff.
Pete. (l33t FS) said:
In reply to Turboeric :
The interesting thing is that a lot of Toyota AWD systems bother to package a center differential in the transverse setup. Learned that the fun way after I removed the driveshaft from a Highlander on a drive-on lift. Oops, we no longer have Park!
A large percentage of Subarus have a center diff, with either a viscous limited slip or a computer controlled electronic one. At least with the 4EATs, the turbo models had a center differential and the non turbo models were FWD-with-clutch-to-rear but I am sure there are exceptions. 99% sure that all manual transmissions without a 4wd lever/button have a center diff.
Yes the Subarus and others have a centre diff, but it only locks up and transmits power to the rear wheels when wheel slip is detected, so the run as FWD until things get slippery. I think that all manual AWD vehicles without a 4wd lever/button have a centre diff, but they're all viscous or computer controlled lockup's, so the rear gets power only when needed. Hybrids like the RAV4 are functionally the same - the rear electric motor only gets powered when wheel slip is detected, or when running at parking lot speeds using battery only. It's one of the reasons a RAV4 hybrid is only slightly more expensive and slightly heavier than an ICE RAV is that Toyota can ditch the centre diff, driveshaft, rear diff - heavy and expensive bits.
As for hybrids not producing engine braking going down a mountain when the battery is full, that's a very rare circumstance (the battery is usually empty from getting up the mountain), and when it is the case, the engine braking is no worse than a conventional automatic in an ICE car.
Turboeric said:
Pete. (l33t FS) said:
In reply to Turboeric :
The interesting thing is that a lot of Toyota AWD systems bother to package a center differential in the transverse setup. Learned that the fun way after I removed the driveshaft from a Highlander on a drive-on lift. Oops, we no longer have Park!
A large percentage of Subarus have a center diff, with either a viscous limited slip or a computer controlled electronic one. At least with the 4EATs, the turbo models had a center differential and the non turbo models were FWD-with-clutch-to-rear but I am sure there are exceptions. 99% sure that all manual transmissions without a 4wd lever/button have a center diff.
Yes the Subarus and others have a centre diff, but it only locks up and transmits power to the rear wheels when wheel slip is detected, so the run as FWD until things get slippery. I think that all manual AWD vehicles without a 4wd lever/button have a centre diff, but they're all viscous or computer controlled lockup's, so the rear gets power only when needed.
That is not how a differential works, a differential applies torque to both ends. You are describing a coupling, not a diff.
Unless the oily bit with the bevel gears and cross pin is an electric clutch and I just could not find wire to it 
As for hybrids not producing engine braking going down a mountain when the battery is full, that's a very rare circumstance (the battery is usually empty from getting up the mountain), and when it is the case, the engine braking is no worse than a conventional automatic in an ICE car.
Which is near zero unless you can manually downshift, which is an option most hybrids do not give you. Why use engine braking when you can charge the battery?
alfadriver said:
Generally, you will not run the system at WOT terribly long, so the ICE has enough power to drive their wheels and the other set of tires via electrical power.
This. A PHEV doesn't ever run out of battery power completely. The ICE engages and helps keep the battery in the proper range, as well as delivering power to the wheels.
A Prius will not move without electric power. The same would be true for an AWD version of it.
mtn
MegaDork
3/21/22 10:32 a.m.
Pete. (l33t FS) said:
The larger concern if you are going down a mountain and the battery is full. You usually can not get engine braking with a hybrid.
IIRC this and the reverse issue (it is 100% electric) is why Escape hybrids are not rated to tow much.
This isn't making sense in my head. Can you dumb it down for me?
In reply to mtn :
For the first bit: Hybrids generally forgo engine braking because they rely so much on regenerative braking. If the battery is fully charged, there is no more capacity for regen, so you are left with just the wheel brakes.
Locomotives get around this problem with huge resistor banks to bleed off energy.
For the second bit, Escapes do not have a Reverse gear in the transmission, so reversing requires use of the electric motor, which is not really strong enough to move a heavy trailer up a hill if necessary.
STM317
PowerDork
3/21/22 4:41 p.m.
Pete. (l33t FS) said:
In reply to mtn :
For the first bit: Hybrids generally forgo engine braking because they rely so much on regenerative braking. If the battery is fully charged, there is no more capacity for regen, so you are left with just the wheel brakes.
Locomotives get around this problem with huge resistor banks to bleed off energy.
For the second bit, Escapes do not have a Reverse gear in the transmission, so reversing requires use of the electric motor, which is not really strong enough to move a heavy trailer up a hill if necessary.
My Ford PHEV will reverse the motor direction (kicking the ICE on) if the battery is too full to accept charge from regen braking. It still regens, just sends the energy through the crankshaft instead of into the battery.
Pete. (l33t FS) said:
The larger concern if you are going down a mountain and the battery is full. You usually can not get engine braking with a hybrid..
In six years of daily driving two different PHEVs, and living in the mountains, I have never encountered this situation.
In reply to Turboeric :
It is rare, yes, but I had read enough reports of it happening that it scared me off of getting a hybrid truck for tow pig duty.
Does the Escape have an engine braking mode like the Prius does?
