The other factor is that Ford may well have an internal standard for towing ability - i.e. must tow X number of pounds trailer up Y% grade for a distance of Z miles at 110 degrees F outside temperature at a some minimum rate of speed. (Think Davis Dam in Arizona) As has been pointed out, once the battery is tapped, you are back to the power of the 4 banger.

 

I think these two are the key points. So I'll probably go ahead and look for a good popup rental and just remember to:

1. Get a scangauge and monitor the differential temp (what temp is high anyway).
2. Try to avoid going uphill in reverse.
3. Monitor battery charge. If it gets real low, pull over and force-charge the pack back up.

Feel pretty armed with the facts... thanks.

11011011

 

I think you will be all right towing a light pop up if you are willing to slow down going up grades. Our FEH revs pretty high when climbing long steep mountain grades (7 and 8%) if I try and keep the speed up around 60 or 65mph. If I back off and slow down to 50mph or so, ICE RPMs drop to a more reasonable level.

I've driven up the 26% grade over Sonora pass without any problems. The ICE rpms never went very high, but I was only going 25 to 40mph most of the time. The FEH can pull quite a hill as long as you don't try and be speed racer!

 

haha... I don't think my Prius Speedo has seen anything north of 55 for over a year ;-). Speeding shouldn't be a problem.... so long as I drive.

11011011

 

You should have no problem towing a pop-up trailer.
Just use common sense, and don't push the car to the Max.
I'm sure it will perform well for you, and surprise you.

I've seen what the FEH is really capable of.
It is capable of pulling 4000+ pounds up a 7% grade at 55 miles per hour.
But just because it can, does not mean you should.

Ford put in a large safty factor.
Probably because this is their first Hybrid line, and didn't know what to expect.
-John

 

Could you state how much weight you were pulling on a 26% grade?

 

Dan — It sounds to me as if you're probably okay. There is, however, another consideration with the Ford and Toyota hybrid systems that hasn't been mentioned so far, and that may in fact be the main reason for their towing limitations. (The Prius and Camry hybrids specify a zero towing limit.) These vehicles can't move forward or backward without electrical power flowing into or out of one or more of the motor/generators. Even when cruising on level ground, a goodly fraction of the power flow from the ICE to the wheels is through MG1 and MG2, without necessarily using the NiMH battery at all. This is because the planetary-gear set (the "Power Split" Device) can't transmit power from the ICE to the wheels without MG1 (the "generator") applying a load to the PSD, either positive or negative. Electrical power is continually flowing either from MG1 to MG2, or from MG2 to MG1 ("heretical mode"). I think the electrical power flow between MG1 and MG2 is likely the limiting factor. When towing, this would be further increased, and could overstress the MGs and/or the power electronics (inverters and dc-to-dc converters) thermally and/or electrically (i.e., over-current). Under prolonged high power conditions, this might be the real reason for concern on Ford's and Toyota's parts.

Stan