Towing with a HiHy in the Mountains

[klc]

We are considering the replacement of our '02 Highlander Non-Hybrid with an '08 Hybrid. However, I am concerned with how well the hybrid will perform when towing a camper over very steep mountain passes. We use our '02 Highlander Non-Hybrid in the summers to go camping in the mountains of Colorado. We usually put about 3k miles on our vehicle during these trips and face steep mountain passes with plenty of stop and go traffic while going uphill. Our '02 huffs and puffs, but it makes it along ok. I have heard mixed reviews on the hybrids ability to pull a trailer uphill. One review read that if starting off from a dead stop on the side of a hill, their '08 hybrid would not even attempt to rev... not even spinning the tires. They reported they had to unhook their trailer and have it towed by a separate vehicle. Towing capacity | Hybrid Cars

We would be in a terrible jam if this happened on a mountain pass.

In most cases we would be pulling a trailer similar to these specs:
3000 lbs Dry Weight
100 gal tanks (usually empty until 30 minutes from destination)
A few 100 lbs in camping gear

If this is too heavy, what types of travel trailors are others towing that are lighter and what kind of performance can we expect?

Seems to me, this wouldn't work well for us. Any thoughts from Hybrid owners?

[efusco]

Originally Posted by klc

We are considering the replacement of our '02 Highlander Non-Hybrid with an '08 Hybrid. However, I am concerned with how well the hybrid will perform when towing a camper over very steep mountain passes. We use our '02 Highlander Non-Hybrid in the summers to go camping in the mountains of Colorado. We usually put about 3k miles on our vehicle during these trips and face steep mountain passes with plenty of stop and go traffic while going uphill. Our '02 huffs and puffs, but it makes it along ok. I have heard mixed reviews on the hybrids ability to pull a trailer uphill. One review read that if starting off from a dead stop on the side of a hill, their '08 hybrid would not even attempt to rev... not even spinning the tires. They reported they had to unhook their trailer and have it towed by a separate vehicle. Towing capacity | Hybrid Cars

We would be in a terrible jam if this happened on a mountain pass.

In most cases we would be pulling a trailer similar to these specs:
3000 lbs Dry Weight
100 gal tanks (usually empty until 30 minutes from destination)
A few 100 lbs in camping gear

If this is too heavy, what types of travel trailors are others towing that are lighter and what kind of performance can we expect?

Seems to me, this wouldn't work well for us. Any thoughts from Hybrid owners?

You should have no issues at all if you stay under the 3500lb cap. The max limit is lower to protect the hybrid components (transaxle, MGs and Inverter) from damage...but the ability is there to tow much more thanks to the excellent low end torque of the electric motors.

Note that the issue of having to unhook at the site you quoted was in snow and loose gravel on a steep hill...that's b/c the traction control kicked in to prevent the wheels from spinning...something that could cause damage to the Motor Generators. If you're careful to avoid towing on steep snowy, slick, gravelly inclines from a stop you'll be fine.

[miscrms]

Originally Posted by efusco

You should have no issues at all if you stay under the 3500lb cap. The max limit is lower to protect the hybrid components (transaxle, MGs and Inverter) from damage...but the ability is there to tow much more thanks to the excellent low end torque of the electric motors.

Note that the issue of having to unhook at the site you quoted was in snow and loose gravel on a steep hill...that's b/c the traction control kicked in to prevent the wheels from spinning...something that could cause damage to the Motor Generators. If you're careful to avoid towing on steep snowy, slick, gravelly inclines from a stop you'll be fine.

Not sure what the HiHy comes with for oem tires, but one would have to speculate that like the Prius it would benefit from a tire upgrade. As you say the issue seems to be traction, not power. In the Prius at least the traction control keeps you from spinning the tires as you could quickly burn out the electric motor with no loading on it.

Good Luck!
Rob

[tochatihu]

In the ideal case, you would have the capability to monitor temperatures of MG1 and the HV battery. My experience with a well-instrumented 2001 Prius, very heavily loaded in mtn driving was that those 2 temperatures can get higher than I'd want them to.

If the Highlander HV battery has a similar cooling system design to Prius, the best way to lower battery T is with the air cond blowing cold and flow-through (not recirc) mode. There is no way to cool off a hot MG1 other than to stop the vehicle in 'ready' and let the inverter coolant pump do its thing.

The CANVIEW for 2004-onwards Prius can show HV battery temps at least, but I don't know about MG1, or if it is compatible with the Highlander. Possibly other equipment (such as scangauge) can show the important temperatures?

All of this may represent an abundance of caution. If you are doing high-load driving and get any sort of caution message on the dash, just don't ignore it.

[klc]

Originally Posted by tochatihu

In the ideal case, you would have the capability to monitor temperatures of MG1 and the HV battery. My experience with a well-instrumented 2001 Prius, very heavily loaded in mtn driving was that those 2 temperatures can get higher than I'd want them to.

If the Highlander HV battery has a similar cooling system design to Prius, the best way to lower battery T is with the air cond blowing cold and flow-through (not recirc) mode. There is no way to cool off a hot MG1 other than to stop the vehicle in 'ready' and let the inverter coolant pump do its thing.

The CANVIEW for 2004-onwards Prius can show HV battery temps at least, but I don't know about MG1, or if it is compatible with the Highlander. Possibly other equipment (such as scangauge) can show the important temperatures?

All of this may represent an abundance of caution. If you are doing high-load driving and get any sort of caution message on the dash, just don't ignore it.

Thanks to all for your replies!

High temperature shut down seem to be a likely scenario, as it seems traction control would at least "rev" the engine. (However, as a Hybrid pupil, I must recognize I certainly do not know any of the ends and outs of how a Hybrid would respond to a transaction issue.)

Let me also mention that when camping in Colorado, a fair distance of travel can happen on gravel roads as one draws closer to the camping area. None of what we do could be classified as "off roading" and I do understand that a Hybrid is not equipped for any off road activity. However, would pulling a trailer as described above be likely to cause an issue when traveling over loose gravel roads?

All input appreciated and welcome!

[efusco]

Originally Posted by klc

High temperature shut down seem to be a likely scenario, as it seems traction control would at least "rev" the engine. (However, as a Hybrid pupil, I must recognize I certainly do not know any of the ends and outs of how a Hybrid would respond to a transaction issue.)

There may be some confusion here. There's no connection b/w the issues of hybrid component overheating and traction control. The overheating would, potentially, be an issue for very long steep climbs with large tow loads...probably in excess of 3500 lbs. The traction control issue only occurs with starts from a stop and at very low speeds(<10mph) when trying to move out of mud, or up an incline that is slick or has gravel.

Let me also mention that when camping in Colorado, a fair distance of travel can happen on gravel roads as one draws closer to the camping area. None of what we do could be classified as "off roading" and I do understand that a Hybrid is not equipped for any off road activity. However, would pulling a trailer as described above be likely to cause an issue when traveling over loose gravel roads?

Once you're moving TRAC really won't be an issue unless you have a very steep area you're climbing slowly. And with good tires even then it shouldn't be a problem, esp. w/ 4WD and a properly balanced load.

[Devil's Advocate]

I have towed 1750lbs with the Prius from Vegas to LA and back, so some 4200 foot passes. My only concern was overheating the MIGs, so I took care to accelerate extra slowly to minimize stress o the electrical motors. After that the ICE took the load.

The ICE was OK except on two of the long inclines when it was running near full RPM's to make enough tourque to get up the hill. 45 MPH seemed to be the fastests the ICE could keep the car going given the load and no electric torque boost.

[miscrms]

Originally Posted by klc

Thanks to all for your replies!
High temperature shut down seem to be a likely scenario, as it seems traction control would at least "rev" the engine. (However, as a Hybrid pupil, I must recognize I certainly do not know any of the ends and outs of how a Hybrid would respond to a transaction issue.)

I would seriously doubt it, based on how the Prius behaves. If the hybrid system was overheated there would have been all kinds of lights flashing on the dash. This sounds exactly like what a few users have reported when they are traction limited. Starting on a loose uphill surface, particularly with a heavy load, is pretty much the worst possible scenario for traction. Since the car has complete control over the power delivered by both the electric motors and ICE it modulates this instead of pulsing the brakes like some vehicles do. If the system detects wheel spin, it drastically reduces power output. The reported symptoms of TC taking over is as if the car has shut down. No pulsing, no spinning of tires, no reving ICE. Just the quiet of the electric motor delivering just enough power to keep the wheels from slipping but not enough to move forward. This seems to occur in situations where the vehicle would not have had sufficient traction to start so the fact that TC isn't letting you try is somewhat irrelevant. Backing down to a flat and getting a little speed up often seems to do the trick, as in most traction limited conditions. There is no way to disable the TC as this would risk damage to the electric motors. The sensitivity of the TC system was supposedly adjusted in the 2006 timeframe, and is much improved. There are also a lot of reports that this is simply not an issue with decent tires. The stock tires were selected for their low rolling resistance, but leave something to be desired in the traction department.

Again this is all with regards to the Prius, based on the assumption that the Highlander is operating in a very similar fashion. I personally would not hesitate to take a HiHy into these types of conditions. Particularly with good tires. From what I can see the HiHy's seem to come with either Goodyear Infinitys or Michelin Energys. Both of these are basically car tires. I went with Yokohama Geolander A/Ts on my Land Rover and they've been great. Not sure how they would affect fuel economy though. Of course you'd probably still get much better mileage in a HiHy with A/T tires than in any other vehicle you might use to tow that load. A/Ts might be overkill for your requirements though anyway.

Rob

[miscrms]

Originally Posted by Devil's Advocate

I have towed 1750lbs with the Prius from Vegas to LA and back, so some 4200 foot passes. My only concern was overheating the MIGs, so I took care to accelerate extra slowly to minimize stress o the electrical motors. After that the ICE took the load.

The ICE was OK except on two of the long inclines when it was running near full RPM's to make enough tourque to get up the hill. 45 MPH seemed to be the fastests the ICE could keep the car going given the load and no electric torque boost.

Thats pretty impressive considering the Prius' towing capacity is 0 and payload capacity is only 863 lbs!

Rob

[Devil's Advocate]

Yes it is. shhhhhh don't tell Toyota. Doesn't really matter now I have 141,000 miles on the car.

THe 1750lbs doesn't include the 3 people and luggage inside the car. Another 600 lbs.

Averaged about 29 MPG for the trips.