OK, so it seems to me that using the internal cabin temperature (blend door opens to the cabin vice to the outside) will result in higher temperature air coming into the battery compartment if the vehicle has been sitting in the sun.

Example, assuming the interior gets up to 120 degrees:

2008: Outside air is let into the battery via the blend door. Air comes in at 95 degrees.

2010: Air inside the cabin is let into the battery via the blend door. Air comes into the battery at 120 degrees. Alternately, if the computer is checking interior temperature (which I hope Ford was smart enough to do, the data is available), the blend door stays closed - but does A/C come to the rear via the vehicle HVAC system? How is this more efficient?

 

I'm sure the TBCM monitors the cabin temperature and OAT to control all air entering the pack in all models. To my knowledge there is no ductwork from the HVAC system in the '10 FEH or FFH to the pack. This means the blend door would remain closed until the cabin temperature is lower than the pack temperature in hot weather. Ford claims they changed the chemistry in the cells in the new packs so they could delete the Aux battery A/C. The problem is the ideal battery temperature range in the '09 FEH did not change in the '10 FEH as Bill posted in this thread. In fact, the ideal battery temperature went down in the '09 manual from my '05 FEH manual. This means the '10 FEH cannot maintain the ideal battery temperature with just cabin temperature in hot weather. The battery is less efficient above and below the ideal temperature of 77F. This is why I keep saying the '09 FEH will most likely be the most fuel efficient non plug-in FEH built. It has the most efficient engine and most efficient battery pack with the last Aux A/C. My hot weather improves my engine efficiency and the pack stays cool and at the ideal temperature with the Aux A/C. The load of the A/C compressor during P&G is minor to keep the pack cool because the engine is more efficient in hot weather.

Now we're finding out the drain on the pack in the '10 FEH with the electric A/C reduces EV time in city driving. With the battery efficiency down with no way to cool it in hot weather, your in a catch 22 or even a catch 44. The engine efficiency is killed by the demand of the generator keeping the pack charged near its lower SoC. One guy posted here his SoC drops 1/10% a second at a stoplight with the cabin electric A/C running in EV. This means not only reduced EV driving but also sitting at a light with the engine running more. Most people are reporting better highway MPG than City and I think it's for this reason.

GaryG

 

The Aux A/C - does it run off the main compressor?

 

Yes, the engine belt driven main compressor is used for both the cabin and the Aux A/C on the '05 - '09 FEH.

GaryG

 

Thanks for your replies, they are improving my understanding. One more:

My understanding is that the 2010 does not have the A/C lines going from the engine compartment to the rear? These can be observed in the left rear wheel well, from what I have read.

 

Those A/C lines go to the Auxiliary Evaporator (Aux A/C) located next to the battery pack in the '05 - '09 FEH. There are no longer A/C lines, an Auxiliary Evaporator, Auxiliary Evaporator Housing or outside vent in the '10 FEH. In the '10 FEH, the only way to get cool air to the pack is from the cabin. If you don't run the '10 cabin A/C in hot weather, your battery temperature will not get any cooler than the OAT. The battery will generate heat while charging on its own so the battery temperature will always be hotter than the OAT (outside air temperature). If you live in a climate that gets hot and don't run the cabin A/C, you lose battery efficiency in the '10 FEH. To make things worse, during the warm-up strategy the battery quickly drains and then needs to recharge getting hotter than the OAT. Think about how long it will take to cool down the cabin to get that battery cooled down in the back of the '10 FEH.

The owners of the '05 - '09 FEH can start cooling the battery as soon as you start the engine during the warm-up strategy without running the cabin A/C in hot weather. Our big compressor can cool our packs in a very short time, and it's all automatically done by the TBCM and the PCM. Ford didn't want the driver to have any control over the Aux A/C and the battery temperature in the '05 - '09 FEH. Ford restricted the '10 control to cool down the battery by removing the Aux A/C and turned the control over to the driver. The TBCM and PCM will still shutdown EV and battery charging to prevent to much battery heat from damaging the battery further.

GaryG

 

Thanks, I think I've got a grasp on the whole system now. It seems to me that this was a poor choice by Ford. Maybe in a northern climate like Dearborn this would be more efficient, but in a warmer climate it makes no sense not to use the main HVAC to cool the battery pack.

 

Anytime Steve

I'm going to hold off until the Ford plug-in models hit the market and evaluate them as far as hybrids anymore. I'm sure glad I was on top of the changes on the '09 FEH and just lucked out that Ford stayed with the Aux A/C and belt driven compressor. I thought I messed up buying the '09 when I found out that the '10 FEH were changing to the electric A/C compressor, but not now.

After testing the BMW X6 Hybrid with an electric A/C compressor last year, I'm now glad the reporters first wanted me to hypermile it with the A/C On. It ate up the SoC so fast in city driving I couldn't even P&G it in EV. This made me rethink getting a FFH for my wife who must have the A/C on all the time.

One last thing, Right Lane Cruiser (Sean) at CMPG explained to me his wife's FFH really burns the SoC when he goes EV at 47mph down to 40mph. Ford increased EV speed also in the '10 FEH to 44mph. Sean said in order to exceed the 40mph EV speed the '05 - '09 FEH is restricted to, Ford raised the EV speed by using the battery to spin the engine with MG1 over 40mph. Now what good did that do! You burn up the SoC in the new models just to increase EV speed. What a joke that is, you can go full fuel-cut down from any speed all the way to 40mph at which you go EV in the '09 FEH. In fuel-cut, the '09 FEH doesn't drain the battery because the wheels and MG2 is holding the idle of the engine during fuel-cut. Here again, Ford made the newer hybrid models less efficient just to say they increased EV speed in them.

GaryG

 

Piece of cake, talked to the rep and said it wasn't bad now, but much worse when it gets below zero. He asked for the TSB #, pulled it up on the screen and said he'd have to order it. Doesn't get much easier than that. I should have asked for the Sync mic update as well.

 

Regarding the tsb for vibration,


Maybe someone should make this a sticky so others don't get screwed by Ford like i did!!!