I think Chris made a good description in post #6.

You only have in the ballpark of 22 Horsepower... maye 25 HP tops in the newer 2008 to use when you are in EV mode.

This is actually enough to maintain speed, at any speed under 60 miles per hour.
But this is not enough HP to accelerate at any speed more brisk than a freight train.

A primary reason for this is the allowable wattage output from the HV battery pack, not a limitation of the electrical motor.
The battery pack in the car is really very small. High voltage ( 330v ) but very small in size capacity wise.
It does not have much more than the 12v battery under your hood. REALLY.

When you are in EV, the Electrical HP is reduced to about 2/3 of normal.
The reason is simple:
The car has to keep 1/3 in "reserve" to "start" the car when the time comes.

So here is an approximate breakdown of how much electrical power you get:

In EV mode, you get 22-25 electrical Horsepower ( 100% from battery )

After the engine is started, you get up to 35 HP 100% from the battery.

When the engine spins the generator ( hybrid drive ) you can get:
- up to 35 electrical HP from the battery and
- up to 35 electrical HP from the generator

You have a "94 HP electric drive motor" installed in your car, but it never ever puts out more than 70 HP because there is not enough electricity to go around. But also this means the motor is being treated gently, and should last a very long time.

To get 94 Electric Horsepower, you would need 70,000 watts ( 70 kW ).
That is 212 amps of current @ 330v.
This car does not have that capacity.

However, this is not designed to be an electric only car!!!
It is a "hybrid car" and hybrid means gas + electric working at the same time.

Hybrid car does NOT mean, electric car city, gas car highway!!!

 

And it does not seem to be consistent either. There are times on a flat road where you barely press the petal down & the ICE starts up at maybe 5 mph, even with plenty of HV battery. There are other times where a stronger petal push will stay in EV from a dead stop up to 20+.

Myself I do think that (traffic permitting) if you can start from a dead stop up to 20~ mph in EV this should also be a big help in fuel usage as you are not using the ICE for the primary portion of the forward inertia, so when the ICE does kick in, not as much power is needed from it as would be from a dead stop to continue acceleration and maintain forward motion until you reach the desired speed.

But then again I don't fully understand why the "sweet spot" for the HV battery is between 40 - 60% where a fully charged HV battery is not used as well.

 

It is the sweet spot for both usefullness and longevity of life.

If the battery was allowed to 'fully charge' then there would be no room for Regen sometimes, and your FE would go down.

Fully charging, or fully dis-charging ( and fully discharging mean a drop of 0.3 volts per cell, not zero volts total, which would kill the battery permanently the first time it happened! ) puts undesired stress on the battery and shortens its life. The same battery in your laptop or cell phone will only last ~ 2 years, since they are allowed a deeper cycle.

Ford warranties their HV battery for 10 years / 150,000 miles, but fully expects them to last 15 years / 225,000 miles.

The battery is allowed to drop below 40% during each cold start-up period, but is kept between 40-60% during normal driving. MOST of the time, probably 90% of the time you are in your car, the battery is kept between 40% and 53% really. So it's very efficient when you look at all it does with that 13% of the battery capacity.

 

I thought the HV warranty was 8-year/100,000 miles?

 

Depends what state you live in.

But if Ford is "comfortable" giving a 10/150k to some states, they are just choosing not to give it to the others, IMHO.

 

With my FEH FWD with 41,000 miles now, I can accelerate to 38mph from a stop if a have no headwinds on flat roads. Most of the time I don't accelerate much above 30mph in EV where I set the speed control. My tires are at 50psi and this helps with everything to improve mileage.

One thing I try to do if no one is behind me, is accelerate using the least amount of battery juice I can. I watch the Assist needle all the time to keep from accelerating to fast in EV and wasting battery juice. After all, the battery juice has to be replaced. To me, it's all about going further with the least amount of energy. If I accelerate hard but still staying in EV, I run out of battery much faster in a shorter distance. Sometimes I have to accelerate hard in EV because of traffic, but I find it's better to kick on the ICE and maintain a low RPM acceleration instead. This allows charging till I get up to speed where I can go EV again at any speed below 40mph.

Bottom line is I avoid accelerating hard in EV.

GaryG

 

Thanks Gary for those tips.
50psi? What is the recommended psi for your tires?
I just want to know how much higher I can go.

 

I don't recommend anyone go over the max side wall of the eco-plus tires which is 44psi. That said, I keep my eco-plus tires at 50psi and other than the harder ride, they perform and wear great in my location. I corner hard to keep my speed and there is no outside wear that I can see. With 41,000 miles, I think I still have at least 30,000 miles left on them. Most likely I will replace them because of noise like I always do with this type of truck tire.

GaryG