It was 2F at 7:00AM and 17F at 4:00PM today. My scanguage reported a TAV value of 37.4. My ICE ran at the 1400 level opposed to 1000 at idle. The hybrid battery underwent a series of charges and discharges in an attempt to warm itself. This series of charges and discharges seemed to lessen itself as the TAV exceed 40F.
Yes I could obtain regenerative braking and increase SOC values-see the 52_+ value. Yes I could obtain EV with the hybrid battery battery at a mid 40 value. Don't believe those that don't own the FEH.

 

I jumped in my 08 FEH this afternoon, the TAV read in the low 20s, and the SOC on my Scanguage read a mere 23%. When I parked it yesterday, the SOC was 54%.

The car would barely back up, I could get no regen braking, and no assist. My car was a dog for the first 8 miles till the SOC came up to 30%. This was the third time the SOC dropped drastically overnight when the temperatures were in the 10 degree F range.

Eventually, the battery warms up, recharges, and the car runs normally again; but I have taken to backing into the garage at night because I cannot be sure it will back out in the morning.

I have tried to get the block heater/battery warmer but my dealer says it is no longer available.

 

The cold weather should not have an effect on losing SOC just from sitting unused overnight. I have not seen this on my vehicle. The following are the parts for the 41H engine block heater. One is still able to purchase these.


There is a "heater" in your hybrid battery
However, starting early in the 2008 model year, the 20 guage wire to the hybrid battery was discontinued. This 20 gauge wire makes it way to the location under the window fluid reservior in the engine compartment. It is possible rig up your hybrid battery heater IF you can work with high voltages.

 

You can purchase the block heater alone for like $30 from NAPA that's where I got mine.
Took like 5 minutes to install, har dpart loosening the 14mm plug below the ex. manifold

 

That won't help my problem...
I suspect there is a bug or problem of some sort with my car. I complained to my dealer last year about the poor cold weather performance. The dealer kept my car for several days, and performed some tests under the direction of the Ford engineers. Ultimately they told me there is nothing wrong with it. It throws no fault codes, it just runs like crap and the battery pack dies in the cold.

 

Have you had the 12V battery tested? If not, can you take it to an independent "battery" shop for this testing and testing for possible drain(s)? I had an issue with mine and did find an undetected drain and bad cell on my 12V battery. I also did experience some hybrid SOC loss with the vehicle sitting.