# of minutes the A/C will run w/o ICE

It varies...

 

The amount of time also depends upon the traction battery state-of-charge at the onset of this little exercise. In general, once the Prius gasoline engine has warmed up and then the Prius is placed in Park, the engine will stay off until the SOC drops down to show two pink bars on the MFD SOC indicator. Then the engine will run to bring the SOC up to three blue bars. This cycle will continue indefinitely.

If the SOC started at eight green bars, the outside temperature was moderate and the inside requested temperature also was moderate, the air conditioning might run on battery power alone for perhaps a half-hour or longer... At some point the gasoline engine might start just to keep the catalytic converter hot, independent of the traction battery SOC.

 

my initial results are, and this is no means an official study of the matter is this

if you turn on AC and leave AUTO OFF, and keep it maybe under 72 or so
the traction battery might be able to keep the a/c going for 30 minutes

if you leave it on AUTO ON with the temprature set to 72 or more and
its kind of cold out, the engine will probably run maybe 10 or so minutes
out of that 30 minute period

to get most of the power out of the traction battery and not have to worry about the engine turning over, keep it in "auto ac off" mode

a/c auto off mode will tend to run the battery towards the low end

aufo on keeps the battery towards medium - high charge, because it needs to run the engine to HEAT the cabin

 

We have to ask in reply, why do you want to know?

If the engine is not allowed to recharge the main battery the A/C will drain the main battery in (variable) short order. If you want to stay in the car with the A/C running leave the car ON and in Park, and let it run the engine to recharge the battery as needed. If you won't be in the car, or if you are in a place where you must not allow the engine to run, then turn the car OFF and do without A/C.

 

just about any answer given will be correct. too many variables to consider

but let me give you a scenario. its rare that i would sit in car with AC on. but there was one time i gave a friend a ride a few years back. temp was mid 80's (very hot for my area), had AC set to 70, but parked in the shade to wait. shade at an angle so it was filtered somewhat, but i say percentage in 90's.

she had some paperwork to drop off. so i sat in car, turned AC up to 74...when not moving and in shade, a lower temp is tolerable. i sat for 30 minutes before engine kicked on. i know this because i noted that the consumption screen was blank. it might have gone longer, but i checked the battery display and it was down to one bar, so i got nervous (plus had to reposition because my shade had moved so i circled the lot once, and it idled for about another 2-3 minutes, after that, she came out and we left, but i drove another 5 minutes before battery got back to normal

 

Ah! For truckers, an electric A/C system (similar to that used in the Prius) is the answer; the option of using shore power should be provided to avoid running the engine at all. Trying to run A/C for hours entirely by battery would require an unreasonably large battery.

 

The problem you are dealing with isn't the inefficiency of air conditioners, it's the inherent amount of power needed for cooling. Even running at the theoretical limit of efficiency, an air conditioning system for a boat or RV is going to draw a lot of power. Look at it the other way around and talk about heating. Say you want to heat your boat electrically, so you put in an electrical resistance heater (just a normal space heater). Resistance heaters are 100% efficient in turning electricity into heat. You will loose some power in the supply wires and battery, but that will also be lost as heat, so it's as good as you can get. Now ask yourself how much heat you need. On our boat we use a diesel fired heater that produces 43,000 BTU/Hr; that's 12,602 W, or roughly 12 KW. If you power that from a 12 V source, you need 1,000 Amps. To run that heater for 1 hour, assuming you are willing to completely drain your battery, you need a 1,000 Amp-hour battery. That's 5 big truck sized 12 V batteries, just for one hour! That's why our heater is diesel fired. Heating and cooling takes a lot of power.

Tom

 

Hey there fellow O.C.'er !
Let me tweek / clarify one other important thing, because it may be important. This cycle WON't continue indefinetely. Worst case scenerio, your last pip is blinking. You leave the AC on and go into the house for a qucik phone call, that ends up taking, oh, say 25 minutes, forgetting you left the car on during a 90 degree day. Car runs out of gas, AC hurries the batteries into discharge . . .

BOOM

now where are you? Yuck.
hey, it's still the tail end of winter / early spring ... who's running the AC?

 

With a Prius there is little difference in "idle" vs steady cruising recharge rates. The M/G is approx 200 VDC, not at all like a 12 vdc alternator. Stuck in traffic on a hot summer day, I've had the motor cycle to keep within 2 pink to 3 blue within a minute.

In normal driving the Prius tries to keep the the battery indicated SOC between 3-5 blue. This is indicated, not actual, which usually translates to around 50% for maximum NiMH battery life. There is also a lot of hysteresis in the indicated battery SOC. The indicated battery SOC is for the NiMH "traction" battery, not the 12 vdc battery

I'm guessing you're thinking of some sort of mobil heat and A/C solution, perhaps for trucking? If that is the case, companies like Teleflex and Carrier already offer a "hybrid" sort of of APU for rail, fixed mobile, and trucking

The same principle as the APU used on jets. Rather than run the turbofans to keep the Air Cycle packs running, the APU can be started and run most aircraft systems, much more efficiently.

Rather than idle a large motor, which is very bad for the motor and also very wasteful, you run the tiny APU. The APU has a very small diesel motor which is run near its rated power, for maximum efficiency

In the case of rail service, the APU allows the operator to shut down the big diesel. Diesel locomotive engines are usually either plugged in to special 3 phase or single phase coolant heaters or left running 24x7 if there is no shore power. Very wasteful

The APU is started and it keeps the starting batteries charged, and the coolant warm. In hot weather it can run an electric A/C. It can also be programmed to monitor engine temp, battery charge, etc and run according to need

Teleflex EcoTrans

Teleflex EcoTrans

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/success/locomotive_apu.pdf

For the trucking industry, the APU allows the truck driver to shut down the motor and let the APU charge the batteries, heat/cool the cab, and in cold weather keep the engine warm. The truck APU can also be programmed to monitor battery charge, and engine coolant temp, and run accordingly

http://www.trucktrailer.carrier.com/Files/TruckTrailer/Local/US-en/trucktrailer/comfortpro.pdf

Of course, the development work that Toyota and Denso did on the hybrid system and HVAC has application in other industries.

 

The Prius has supplemental PTC electric resistance heaters to aide in defrost at very low temps. A similar system is used in new Ford Super Duty trucks with the PowerStroke diesel, as diesels are coldblooded.

IMHO the Prius could have incorporated higher output electric heaters, the ones now installed run off 12 vdc. They could have easily incorporated 200 vdc heaters

Of course, there are probably more Prius sold in LA than all of Canada, so Toyota couldn't offer such a system to satisfy a teeny percentage of Prius drivers. The Ford SuperDuty system is optional, but a contractor I know who has it in his new Ford F-450 swears by it

Remember the Prius A/C is very efficient, far more so than the average car A/C, as the compressor is variable speed. If you have the hood open on a hot day while the A/C is running, you can hear the compressor vary in pitch as it speeds up or slows down

Conventional wisdom tells us it's better to put up with a hot car and A/C off to gain 1-2 MPG. With the Prius, if you run the interior hot, the battery pack will "derate" itself to protect itself, and the car will perform like a dog.

In the Prius, the battery pack is most comfy when we are most comfy. Although bitter cold temps can also somewhat derate the pack, hot temps have a much more immediate effect. So running the Prius A/C is more efficient than keeping the interior hot

 

That is not entirely correct. On a SEER basis the little window units are among the most INefficient on the market! This depends on your cooling needs

For example, with a house you should not have windows facing West, SW at all. When the summer sun is setting, you have enormous solar gain from those windows

For winter, you want windows that face SE and S, to get "free" heat when its very cold. However, in summer you want a good overhang on the roof to keep direct summer sun off those windows.

It's fairly easy to design a house to incorporate passive heating, with correct design of the roof overhang to minimise summer solar gain.

Combine with good attic insulation, and proper attic ventilation, and good home design overall, the cooling need is greatly minimised.

To cool an entire house, central air is usually more efficient - and cheaper - than running a window A/C. There are modern variable speed air handlers and multi speed A/C condensers that can achieve SEER of +18. I have the Bryant Evolution and am very impressed with the performance and operating cost

The Evolution Heating and Cooling System - Bryant

The exception if you only need cooling in just 1-2 rooms. It also depends on where the air supply/return is located

Air supply and return in the floor is traditional for a cooler climate, otherwise the floor is freezing cold in winter. However, this allows air stratification in summer, since the warm air will collect at the ceiling. Ceiling fans help

For partial cooling a home, a ductless system is actually the most efficient. The evaporators are located near the ceiling, and the system only runs when need be

Mitsubishi Electric - HVAC Advanced Products Division

If you're thinking of an off-grid solution, then you might as well give up on any sort of A/C. Cooling is very expensive no matter which way you look at it.