I like the setup Honda uses. The compressor has two drives, a regular one which runs off the belt and a small (like 15cc capacity IIRC) electrically driven compressor which runs during idle-stop. They are integrated into one unit and the belt-driven shaft re-engages as soon as the engine starts. Photo of the unit as set up on a HAH is here:

http://alternativefuels.about.com/od...compressor.htm

The FEH with its large battery would be well suited to a similar arrangement. I also think it would be cool (pun intended) if the compressor was fitted with a timer so that it would only run for, say 90-120 seconds, thus limiting battery drain. That would suffice for the majority of idle-stop episodes. Call it: A good compromise.

 

Interesting, for sure.
More comfortable for the driver? For sure.

Better for FE? Not sure!

 

I think it's safe to say that A/C is always bad for FE for in-town driving. The best thing for FE, short of not driving in town, is driving in town with the A/C off. But that's not always possible or realistic, especially when it's 99° as it was in Denver yesterday. I didn't drive yesterday, but if had I would have been either roasting or turning the ECON button in my FEH to off.

While not perfect by any means, a compressor design like Honda's would nearly eliminate one significant shortcoming of my FEH: Forcing me to choose comfort over economy.

Electric A/C (a la the Prius) saps battery power. ICE-driven A/C saps the in-town fuel economy gain of an idle stop system. But a "hybrid" A/C compressor impresses me as the best compromise.

 

Yes but what is the cost of that puppy? Cus its gona fail sooner or later.

 

I, too, was a fan of a hybrid (FEH, MMH) using an electric compressor so that one continues to enjoy A/C when in EV mode.

However, after long debate here, I changed my mind. The new factor for me, is that a real electric A/C would suck down battery power so quickly, that one would end up with the ICE running anyway; just to charge the now dead battery instead of running the A/C directly.

I don't know if a hybrid A/C compressor would no longer suck down battery power when in EV mode.

 

E=MC2 or there is no free lunch. An electric compressor that could flow enough freon at idle would suck the batt down fast, a hybrid compressor would cost a bunch. Also electric compressors, when they go out burn the freon and make a HUGE mess of the system. I think from a cost benefit analysis the current system is a good compromise. I would like to see a thermostat controled a/c compressor that would cycle the ICE instead of blending heated air, but in traffic on a hot day the a/c is going full tilt, so this would only help highway speeds.

 

"cycle the ICE instead of blending heated air,..."

You can "force" the blending aspect, REHEAT/REMIX, OFF by using maxium cooling, lowest temperature setpoint, recirculate, and then adjust to the lowest blower speed that will still maintain your cabin comfort level. Route the airflow from the footwell or combination dash/footwell so that the resulting COLD system airflow doesn't discomfort you to excess.

Oftentimes if the OAT is below your comfort level you might want to use the A/C to initially cool the cabin but then switch it off.

The above procedure will raise the efficiency of the A/C, climate control system, dramatically. The compressor clutch cycles a lot less often, improving FE, and maybe the ICE controller will do the same.

 

Not sure but I think most automotive systems use a low side pressure corresponding to about 40° for compressor shut off. Mark says it's closer to 33° in the FEH. That explains why most of you are saying the compressor runs almost continuously.

Perhaps they changed the design for 2008, as mine cycles the compressor on/off similarly to other cars I've owned. It runs non-stop when there's a big demand. But once the interior temp is stable, if outside temps aren't too extreme, it cycles fairly normally.

The Prius I owned with electric A/C increased/decreased compressor speed instead of cycling on/off. It was a weak system, but could cool the car fairly well for about 5-7 minutes before the battery was drawn down to the point that the ICE would begin cycling. That tells me that an elevtric comressor does, indeed, draw some serious power.

 

Is it better to run the ICE to get air at a stoplight, or use up the recovered energy in the battery.

If you are going to run the AC when stopped, does it make a difference where the recovered energy is used?

 

Both questions are dependent on the source of the energy to be "recovered" from the hybrid battery. If it was "free" via the use of regenerative braking, then assuming you are going to run the A/C, why not.

But if the ICE was used to generate the hybrid charge to begin with...

In any case it will ALWAYS be better for FE to NEVER use the A/C nor heater and ALWAYS drive in a straight line.

Personally I would put a clutch pedal, a virtually non-functional clutch pedal, into the FEH/MMH that only actuates a switch. The switch signal would then be used to let the hybrid control system know NOT to use regenerative braking and thereby extend my (intentional) coasting distance. On the other hand if I don't depress the "clutch" pedal that would indicate my willingness to allow the sytem to use regenerative braking as substitute for actual engine compression braking.

Or like my Craftsman riding lawn mower, the initial travel, say 1", of the brake pedal could be used to simulate the virtual clutch pedal function. If I lift the gas pedal and then step "lightly" on the brake pedal that could be used as an indication that "braking" is permitted.

Otherwise....

Let me "coast" as far as the laws of physics allow.