Increased Milage/APU Idea

I am planning to biuld an APU system because I'll be darned if those things are worth $9-12k that they are asking. While I have most of it worked out I came up with an addition to the unit that I'd like some feedback on.. By all means pick it apart because every bug worked out on the drawing board is one I don't have to fight later...

My primary concern is with reguards to AC since theres a multitude of ways to take care of heat issues ( webasto, ceramic heaters, extra blankets LOL). My concept is electric powered from a bank of 4-6 AGM batteries. Using and Isolator (pick#1) , An electric motor driven compressor (Pick#2) and controled by a digital thermostat(Pick#3)
I would remove the existing compressor and tie in the new unit to my existing truck system utilizing the condensor, evaporator and blower unit already in the truck. Obviously powered by the bank of AGM's and a high output alternator if needed. The thermostat would be connected to the compressor, blower and electric fan for the condensor. This would allow the unit to cycle by temp just like a home unit.

All of that I seem to have worked out, but I came up with one more idea. Since I am planning to add an electric fan to blow air through the condensor while parked couldn't I also just eliminate the entire fan clutch assembly for a set of electric fans? The reason for this is that it is my understanding that the fan draws 30-50 HP each time it runs which obviously cost money in fuel. By eliminating both the AC compressor and the standard engine fan there should be a significant increase in milage. My thoughts were to install 4 draw through fans on the back side which would be activated by the solenoid switch that currently controls the fan clutch. A set of 2 push fans on the front which would be used to cool the condensor when parked. There it is guys and gals. Have at it... Pick it apart and don't be shy. I'd rather redraw my plans a hundred times than have it blow-up in my face and cost me money because I missed something somewhere in the design. Thanks in advance for your ideas.

 

Thats one of the things I still need to research is whether the electric fans will be enough for the primary engine cooling. I need to determine what cfm the current fan pulls. Then I'll have to go from there.

I kind of drew from a few different APU's on the market and combined parts of them to what I felt would be the most cost effective combination overall from each of them.

Just watch next week some big corperation will be selling my idea and I'll still be broke.

Oh I forgot to add, if anyone has any suggestions / preference for AGM batteries then fire away. Thanks

 

Thanks for all the input. It looks like my quest to eliminate the primary will not work. Not only is the required CFM too high to feasably power enough electric fans but an important fact of the failsafe was brought to my attention. If the fan clutch or any part of the system goes bad then the fan will run all the time to protect the motor. I also learned that the fan clutch does have an AC relay which is why mine was cycling so much the other day.

By eliminating the engine driven AC compressor that alone will minimize run time on the primary fan and idle time so significant fuel savings should still be seen. The electric AC compressor is 450 dollars BTW. I may look at alternative that I can build. Perhaps a GM york style and an elctric motor tied together. I'll keep everyone updated as I learn more from my research. Still looking for input on AGM batteries. Thanks

 

b2bmotor-manufacturer is the manufacturer of the AC compressor I found. They also have an integrated unit for a little more $ but I prefer the split to be able to service motor or compressor as needed.
The unit I am consiering also uses slow/soft start-up technology for increased battery life.
The Kool rig is nice but again its nearly 5000 dollars. Its far better than the 9-12k of most units out there but you are adding several components that are already on the truck (condensor, evaporator, blower, vents/tubing) My design adds only batteries and repositions the compressor and pusher fans on the radiator. The only weight increase is that of the batteries and a set of plastic fans. Their claim is that they use only 2 batteries but that is only for the sytem. What about powering fridge, tv, pc, COFFEE POT etc. That is why I am designing mine around 4 AGM batteries.
There is a claim that a higher output alternator will be needed. I haven't run the numbers but I would think that 10-14 hours run time will be quite sufficient to re-charge the batteries from a stock alternator even if the unit is used while driving. I'll have to check the output of my stock unit and do some more math. LOL