Gary, Really! That could be a factor as I'm still running with the 12v battery that came with the car when new. Typically I have to change out those (usually cheap) OEM batteries within two years. Haven't had any issues with difficulty starting, but then it's hardly ever cold here. How bad was yours, if you remember, when you changed it? Barely crank the engine? Other indications of weakness? I'd happily go buy and install a new Interstate or other quality battery if that's my problem.

John

 

The 12V battery only needs to trip a relay for the HV battery and Motor/Generator 1 (MG1) to spin the engine to start the FEH. There is no starter to crank the engine with the 12V battery in our hybrids.

I had no clue one of the batteries was bad till I checked it. I have replaced two batteries in my '05 FEH and one in my '09 FEH before selling them. The generator has to work harder to keep the 12V battery charged and maintaining the 12V system components like power steering, brakes and fans when the 12V battery is weak. The engine uses more gas turning MG1 to supply the 12V system.

You still have a problem with Assist and the 12V battery would not cause that.

Gary

 

Well, color me embarrassed. You'd think after driving this SUV for 5 years I'd know more about its systems and workings. *Big Shrug* Well, now that my ignorance is evident to all who follow these posts, let's move on!

I will get the 12v battery checked, but I think you're right in saying I still have an Assist problem. I'll keep you abreast of my progress(?) and what I find as I check the things you've recommended.

John

 

Don't sweat showing your ignorance. Very few folks, even among readers of forums like this (let alone the general population) realize how hybrids truly differ from traditional drivetrains.

GaryG et al have offered good advice. Allow me to reemphasize Billyk24's suggestion of picking up a ScanGauge. Program it to show at least battery and motor electronics temp and see what is shows. Diagnosing problems like these without one is much more difficult.

Worst case, if you don't want to keep it after your problem is solved (though I think it's a very worthwhile tool to keep on hand), you can sell it for only a small loss.

 

Thanks, elborak! I plan to buy (probably online) a ScanGauge II ASAP. Been wanting one anyhow, and now I have a good reason to go ahead and do it. Heck, I paid $110 for the dealer to run their test showing everything as normal!

John

 

I have a scangauge in all three of my Fords. Price around, but as a free member of cleanmpg.com, I think there going for $134 shipped.

Gary

 

Gary, et al: Thanks for the tip. I just joined CleanMPG and ordered the ScanGauge. Best price by far, and no shipping or sales tax. Sweet deal!

John

 

Thank my friend Wayne Gerdes, the owner of cleanmpg. A bunch of us know and talk to the inventor of the Scangauge, James Delong since 2005 when I tested his first scangauge for hybrids. Back then, The Scangauge was more than 4 times the size of it now. There is a member at Cleanmpg (CarlD) that worked with Delong to get special X Gauge programming for Ford Hybrids and plug-in hybrid like my C-Max Energi. I still use him for newer X-Gauge programming.

Gary

 

Gary (and others), A quick update.
Three days ago I set my A/C back to "Econ" mode, reset my average fuel economy reading to zero, and started driving around town below 40 MPH with long coasting stops and slow acceleration (much to the chagrin of drivers behind me). We had a couple of cloudy days with showers around, so I didn't suffer too much from the intermittent cooling. Today (hot again), I came home from a short drive, put the car in Park, hopped out with the key still on and checked the HV fan A/C lines where they enter the battery compartment -- the return line was COLD, not just cool, while the smaller pressure line was about ambient temp (95 or so).
Current average fuel economy reading is 26.6. That is slightly higher than I was averaging when I just drove the speed limit with full continuous A/C and no real effort to economize. I'll see what the mileage calculates to be when I next fill the tank.
I'm still not convinced I'm getting as much "assist" during accel as I used to, but maybe I had just slipped into careless habits and it really affected my mpg. I didn't THINK I was driving any differently from before, and I'd never seen less than 24 mpg in the past. I'll keep posting for a bit and let you know what happens from here forward. If nothing else, I'll have received a good primer education on some of my car's systems from you guys, I'm getting a ScanGauge, and I've eliminated SOME of the suspected possible causes of my horrible 19.1 mpg experience.
My sincere thanks to all. More to come.

John

 

The slow acceleration thing is not always the best way to drive as it can eat up SOC rather quickly. Done at the wrong time, drivers behind you are not going to be friendly.