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Experts Only - Re-Engineering Semi Truck A/C Pages: 12

Shepherd777 on Sun June 20, 2010 9:48 PM User is offlineView users profile

Year: 2010
Make: AirFlow
Model: SuperTruck
Engine Size: ISX
Refrigerant Type: R134a
Country of Origin: United States

Gentlemen -

I am converting a belt-driven Sanden A/C Compressor to a 12 volt battery powered Sanden compressor.

The new electric compressor is under the bunk of the sleeper unit, whereas the belt-driven one was mounted on the diesel engine.

It is a dual evaporator system with the second one in the sleeper unit.

I would like to relocate a "T" fitting from near the forward expansion valve on the firewall, to near the expansion valve under the bunk, where the 12 volt compressor is located.

These "T" fittings are on the Suction low-pressure side.

The OEM config is the top image, the proposed re-design is the lower pic.

Can anyone see any problems or issues with the proposed re-configuration?

OEM A/C System">

Electric A/C Routing">

Battery A/C Compressor">

Comments or questions will be entertained.

Thanks in advance.

Edited: Sun June 20, 2010 at 10:47 PM by Shepherd777

HECAT on Mon June 21, 2010 10:05 AM User is offline

I don't think there is any real issue with where the T is located. Just wondering if the 12v "no idle" system compressor is equivalent in displacement and function (variable vs fixed) as the belt driven unit. I would discuss this with Sanden.

-------------------------



HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Mon June 21, 2010 11:09 AM User is offline

Just a little confused on the return of the sleeper evaporator unit, but guess that I am not an expert. That tee in either the upper or lower drawing feeds both the compressor suction and the sleeper evaporator, is that suppose to be different? Its functionally still the same, and since this is a schematic type drawing the actual physically layout would be laid out differently, but still functionally the same.

See this Manual explains the advantages of the electrical system, states the motor can draw as great as 220 amps, but really doesn't tell where you are getting this power from. A bank of submarine type batteries?

Shepherd777 on Mon June 21, 2010 11:52 AM User is offlineView users profile

Quote
Originally posted by: HECAT
I don't think there is any real issue with where the T is located. Just wondering if the 12v "no idle" system compressor is equivalent in displacement and function (variable vs fixed) as the belt driven unit. I would discuss this with Sanden.

Thanks for your input HECAT.

Yes, this 12 volt Sanden should transparently replace the belt driven Sanden.

Shepherd777 on Mon June 21, 2010 12:10 PM User is offlineView users profile

Quote
Originally posted by: NickD
Just a little confused on the return of the sleeper evaporator unit, but guess that I am not an expert. That tee in either the upper or lower drawing feeds both the compressor suction and the sleeper evaporator, is that suppose to be different? Its functionally still the same, and since this is a schematic type drawing the actual physically layout would be laid out differently, but still functionally the same.



See this Manual explains the advantages of the electrical system, states the motor can draw as great as 220 amps, but really doesn't tell where you are getting this power from. A bank of submarine type batteries?

Hi NickD. Thanks for your input.

I'm no expert, but as far as I see it, I don't agree with your following assement:
"That tee in either the upper or lower drawing feeds both the compressor suction and the sleeper evaporator, is that suppose to be different?"

Both "T'" locations should feed the compressor suction inlet from the forward cab expansion valve and the sleeper expansion valve. The freon is sucked from both expansion valve locations and is fed into the compressor suction side. Correct?

One can see the OEM hoses going into the sleeper evaporator valve in the lower left of the pic below. This is where I intend to put the new "T" to draw freon from that expansion valve and the firewall mounted expansion valve.

What I am saving here is not adding an additional suction side hose from the electric compressor all the way to the OEM "T" on the firewall. I'll just "T" into that suction hose going thru the floor and put a 90 degree elbow where the firewall "T" was.

Yes, you are correct about the batteries. They are certified for submarines, aircraft, operating rooms and all other human occupied environments. They are four Odyssey PC-2150 Group 31 batteries. Odyssey Battery

I wouldn't want to sleep on top of any other battery. The Odyssey's are completely sealed and emit no gasses. Using any other type of batteries in this location, one might wake up dead.

Battery AC">

Edited: Mon June 21, 2010 at 12:27 PM by Shepherd777

Rick-l on Mon June 21, 2010 12:48 PM User is offline

How come they don't tell you how many amps it draws while running? That must be one big alternator.

Shepherd777 on Mon June 21, 2010 12:55 PM User is offlineView users profile

Quote
Originally posted by: Rick-l
How come they don't tell you how many amps it draws while running? That must be one big alternator.

Amp draw would vary due to ambient temp and head pressure. There will be a 12 volt fan on the condenser.

The alternator is a new fuel-saving Delco Remy 40SI @ 300 amps.

It also feeds 4 segregated start-up batteries in the OEM location via a battery isolator.

Edited: Mon June 21, 2010 at 1:02 PM by Shepherd777

bohica2xo on Mon June 21, 2010 1:38 PM User is offline

Nick:

That manual has a few contradictions, but the numbers are close to right. They claim 15nm @ 2000 rpm. 4.21 hp or so.

745w / hp, so @100% eff. = 3136w The chart claims efficiency in the 90th percentile, so a probable draw of 3484w

At a very conservative 14.7v that would be 237a. At a battery voltage of 12.9 the current skyrockets to 270a.

But then thay recomend a 200a circuit breaker. 1+1=3 at this point. Perhaps the little scroll is not loading the motor beyond 180a in operation, but there is no way to say from that sheet.

I don't know how long (or how well) the scroll from a Honda Civic will cool a sleeper equipped class 8 truck, but perhaps we will know after he completes this install. Looks like the max cooling available is 15k btu/h on a cool day, and perhaps less than 10k btu/h with higher ambients.


Bob:

After years of flogging banks of group 31 AGM batteries, I can say this will be hard on alternators. With a dozen batteries in the bank & a 7.5kW load it was not as bad as this install. Figure 85ah per battery without killing them. That is 340ah for the bank pictured. At 170 amps, that is two hours of operation. That 170a load would need to include the cabin fan(s), as well as a suitable condensor fan for engine off operation.

The "drive off" load is awful. Not only do you need 170a to keep the compressor cooling as you drive, but you need another 120a to charge the battery bank back up. We beat up some alternators more than a little bit. A Niehoff C716 solved the charging problem, but it was not a cheap unit.

Keep us informed on your progress.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ice-n-tropics on Mon June 21, 2010 1:43 PM User is offline

Shepherd,
Motor and alternator manufactures typically don't show efficiency curves that are real life. Those 90% dubious efficiency data points are at low ambient temps (approx 70 deg F) which are not real life. The motor cooling intake should not be the sleeper evaporative outlet air and exhaust should not dump into the sleeper, to avoid counter-productive A/C COP.
But, it may be productive to A/C the batteries as is sometimes done with Hybrid green vehicles.
I worked on a "Pony Pac" no-idle sleeper A/C WITH 2 COMPS AND ONE CONDENSER. It would keep HeCat happy cleaning up the comp dumps.
An interesting design is the Civic Hybrid with a 2 scroll compressors inside one housing. One belt driven and one with a high voltage electric motor so that they both draw oil from the same sump.
I wonder why OMEGA uses the TR90 instead of the TRSA50 with a built in oil separator which can run higher rpm with a smaller cheaper motor? The TRSA05 can survive with a low total A/C system oil circulation ratio (OCR) of about 1.5% while the TR90 needs 5 % or more.
I would be looking at a 24 v sleeper system with a 24 Volt HumVee alternator
Cordially,
hotrodac


-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon June 21, 2010 at 2:10 PM by ice-n-tropics

NickD on Mon June 21, 2010 1:47 PM User is offline

Certainly the current would be far less if operated well under the 40,000 BTH/Hr specification, my motor does very well with a 15.5K unit cooling 1,500 CF, and it certainly doesn't run 100% of the time. With 4 ea 100 AH batteries, feel you should be okay, especially if you sleep at night without that bright sun. How many CF are you cooling? Would be nice if Omega would show a curve of input current versus BTH/Hr. capacity.

Your batteries would last longer if you could somehow control the charge rate, a 300 amp alternator would tend to charge them very quickly, charging each battery at a 20 amp rate should have them fully charged in less then six hour if bone dead.

NickD on Mon June 21, 2010 1:48 PM User is offline

Oh, nice looking dog by the way. Does your dog travel with you?

mk378 on Mon June 21, 2010 2:00 PM User is offline

Like Ice said, it's really hard to keep the oil flowing right with dual evaporators, and the scroll compressor doesn't like either too little or too much oil. Mostly for that reason, I'd split it into two independent systems. Electric for the sleeper bunk and conventional engine driven for the dash vents. When sleeping, you'd want all available battery power cooling the sleeper. While driving it's inefficient and needless to convert power to electric and back again. Fit a new condenser for the sleeper system somewhere on the outside such as the back wall of the cab. It doesn't need ram air since it would have full time electric fans. Also it'd be worth going 24 volts, but that may be moot since you already bought the 12 volt version.

Edited: Mon June 21, 2010 at 2:02 PM by mk378

Shepherd777 on Mon June 21, 2010 2:41 PM User is offlineView users profile

Quote
Originally posted by: bohica2xo
Nick:



That manual has a few contradictions, but the numbers are close to right. They claim 15nm @ 2000 rpm. 4.21 hp or so.



745w / hp, so @100% eff. = 3136w The chart claims efficiency in the 90th percentile, so a probable draw of 3484w



At a very conservative 14.7v that would be 237a. At a battery voltage of 12.9 the current skyrockets to 270a.



But then thay recomend a 200a circuit breaker. 1+1=3 at this point. Perhaps the little scroll is not loading the motor beyond 180a in operation, but there is no way to say from that sheet.



I don't know how long (or how well) the scroll from a Honda Civic will cool a sleeper equipped class 8 truck, but perhaps we will know after he completes this install. Looks like the max cooling available is 15k btu/h on a cool day, and perhaps less than 10k btu/h with higher ambients.





Bob:



After years of flogging banks of group 31 AGM batteries, I can say this will be hard on alternators. With a dozen batteries in the bank & a 7.5kW load it was not as bad as this install. Figure 85ah per battery without killing them. That is 340ah for the bank pictured. At 170 amps, that is two hours of operation. That 170a load would need to include the cabin fan(s), as well as a suitable condensor fan for engine off operation.



The "drive off" load is awful. Not only do you need 170a to keep the compressor cooling as you drive, but you need another 120a to charge the battery bank back up. We beat up some alternators more than a little bit. A Niehoff C716 solved the charging problem, but it was not a cheap unit.



Keep us informed on your progress.



B.

Hi bohica2xo -

I bought the unit from the 12 volt motor mfg., not Omega. He told me to use a 150 amp fuse. He initially said use a 100 amp fuse. I hope he knows something we don't.

I have a 4/0 welding cable going from the alternator to the batteries.

How do you feel about that re-located "T" fitting on the suction side?

Shepherd777 on Mon June 21, 2010 2:48 PM User is offlineView users profile

Quote
Originally posted by: ice-n-tropics
Shepherd,

The motor cooling intake should not be the sleeper evaporative outlet air and exhaust should not dump into the sleeper, to avoid counter-productive A/C COP.


hotrodac

hotrodac -

Did you mean to say: "The motor cooling intake should not be NEAR the sleeper evaporative outlet air and ELECTRIC MOTOR exhaust should not dump into the sleeper"

???

There are two vents on the rear of the cab to the outside air, one of which is directly behind the new compressor.

Shepherd777 on Mon June 21, 2010 2:50 PM User is offlineView users profile

Quote
Originally posted by: NickD
Certainly the current would be far less if operated well under the 40,000 BTH/Hr specification, my motor does very well with a 15.5K unit cooling 1,500 CF, and it certainly doesn't run 100% of the time. With 4 ea 100 AH batteries, feel you should be okay, especially if you sleep at night without that bright sun. How many CF are you cooling? Would be nice if Omega would show a curve of input current versus BTH/Hr. capacity.

Your batteries would last longer if you could somehow control the charge rate, a 300 amp alternator would tend to charge them very quickly, charging each battery at a 20 amp rate should have them fully charged in less then six hour if bone dead.

That Delco Remy unit has a sensor circut on it that connects directly to the Odyssey's main positive terminal. Hopefully they have the charge rate thing correct with that function.

Shepherd777 on Mon June 21, 2010 2:57 PM User is offlineView users profile

Quote
Originally posted by: NickD
Oh, nice looking dog by the way. Does your dog travel with you?

Thanks. That beautiful girl dog, Dallas, passed away about a year and a half ago, 2 days before her 14th. birthday.

I had 2 other GSD's, mom Zephyr, and her son Bismarck, who rode with me 30 years ago.

I have been retired from driving big trucks over 25 years.

We are just building just one new truck. My current and number 4 GSD, Kayla, will be traveling with me for just a few months to demonstrate the new truck. She is 4 1/2 and looks just like Bismarck, on the right in the pic below, from 1980.

Digby">

Edited: Mon June 21, 2010 at 4:10 PM by Shepherd777

Shepherd777 on Mon June 21, 2010 3:01 PM User is offlineView users profile

Quote
Originally posted by: mk378
Like Ice said, it's really hard to keep the oil flowing right with dual evaporators, and the scroll compressor doesn't like either too little or too much oil. Mostly for that reason, I'd split it into two independent systems. Electric for the sleeper bunk and conventional engine driven for the dash vents. When sleeping, you'd want all available battery power cooling the sleeper. While driving it's inefficient and needless to convert power to electric and back again. Fit a new condenser for the sleeper system somewhere on the outside such as the back wall of the cab. It doesn't need ram air since it would have full time electric fans. Also it'd be worth going 24 volts, but that may be moot since you already bought the 12 volt version.

Hi mk378 -

I can't split it into 2. I completely removed all the belt driven stuff and the OEM compressor. Cummins engineers helped me re-design the belt system.

We do not want any parasitic engine loss in the day time, and want day and night time cooling. So it's electric only.



Edited: Mon June 21, 2010 at 3:23 PM by Shepherd777

ice-n-tropics on Mon June 21, 2010 6:26 PM User is offline

Bob,
For max A/C cooldown in the cab and sleeper there should not be much exhaust of occupant air, therefore operate in the max. recirculation mode.
12 volt motor cooling air should not exhaust back into the cab or sleeper or sleeper evaporator air inlet.
If there is a natural flow through ventilation/leaks of enough air to cool the motor and exhaust it out of the vehicle then the motor will not heat the interior air.
The typical class 8 truck has roughly about 22000 to 24000 BTU dash air and 12000 btu+ of auxiliary sleeper A/C air.
You might consider a air separation curtain between the cab and sleeper to optimize the limited battery stored energy.

JMHO: The presentation claims of eliminating parasitic engine losses for a belt driven comp won' fly in my book. You are about 30 to 40% less efficient in the mobil mode with the battery powered compressor verses a conventional belt driven compressor.
Engine compartment alternator is only 70 to 80% efficient at actual operating temp. The A/C comp motor will also run hotter than the chart. Have a look at the Sanden hybrid scroll for the Honda Hybrid for the optimum solution.
hotrodac


-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon June 21, 2010 at 6:52 PM by ice-n-tropics

NickD on Mon June 21, 2010 7:16 PM User is offline

Efficiency probably comes into play by not having to run that big diesel engine all night like many truckers do. But do agree, some of it is lost by getting taking the compressor off engine for the main cab cooling. Not sure about the alternator, past ones were only about 50% efficient, but can't see a great deal of improvement there, then the battery charging and discharging inefficient, at least another 15%, and the motor inefficiency anywhere form 10 to 30%. adds up. Probably 40-50% overall if lucky, but measurements would confirm that.

Then the replacement cost of the batteries as they won't last forever, even lower if they are fully discharged over night. I also wondered why the entire system was replaced when only the sleeper was in question. Also wonder about winter time, probably more so in Wisconsin, typically, even in the summer, night temperatures are in the 60's. But those long cold winter nights.

Shepherd777 on Mon June 21, 2010 7:46 PM User is offlineView users profile

Quote
Originally posted by: ice-n-tropics
Bob,
JMHO: The presentation claims of eliminating parasitic engine losses for a belt driven comp won' fly in my book. You are about 30 to 40% less efficient in the mobil mode with the battery powered compressor verses a conventional belt driven compressor. Engine compartment alternator is only 70 to 80% efficient at actual operating temp. The A/C comp motor will also run hotter than the chart. Have a look at the Sanden hybrid scroll for the Honda Hybrid for the optimum solution. hotrodac

ice-n-tropics -

If one completely removes the belt-driven compressor, and the alternator is always putting out 300 amps, how can you say we have not eliminated the parasitic losses from

the belt-driven compressor?

Edited: Mon June 21, 2010 at 7:58 PM by Shepherd777

Shepherd777 on Mon June 21, 2010 7:57 PM User is offlineView users profile

Quote
Originally posted by: NickD
Efficiency probably comes into play by not having to run that big diesel engine all night like many truckers do. But do agree, some of it is lost by getting taking the compressor off engine for the main cab cooling. Not sure about the alternator, past ones were only about 50% efficient, but can't see a great deal of improvement there, then the battery charging and discharging inefficient, at least another 15%, and the motor inefficiency anywhere form 10 to 30%. adds up. Probably 40-50% overall if lucky, but measurements would confirm that. Then the replacement cost of the batteries as they won't last forever, even lower if they are fully discharged over night. I also wondered why the entire system was replaced when only the sleeper was in question. Also wonder about winter time, probably more so in Wisconsin, typically, even in the summer, night temperatures are in the 60's. But those long cold winter nights.

NickD -

It is against the law to idle a diesel engine for more than 5 minutes in most areas. California will have you in handcuffs doing so.

The 2 reasons we completely removed the belt-driven compressor were to:

1. - Save diesel fuel in the daytime, as running just an alternator takes less fuel than to run an alternator and a belt-driven A/C compressor.

2. - Save diesel fuel and comply with anti-idleing laws at night time. We don't need 450 hp just to keep cool at night. And if we were to break the law and idle the big ol' Cummins just to keep cool, the fuel used overnight would more than pay for the batteries 5 times over, during the life of the deep-cycle batteries.

So you guys are talking efficiency, but it's a different efficiency. The only efficiency we care about is mpg.



Edited: Mon June 21, 2010 at 8:12 PM by Shepherd777

ice-n-tropics on Mon June 21, 2010 9:28 PM User is offline

Bob,
Alternator power input is in direct proportion to alternator output. If battery is charged and loads are low then alternator does not put out 300 amps as you claim.
2 cents: Loss of fuel mileage because of poor grasp of energy for electrical efficiency (non belt A/C comp) verses belt drive on the road will cause you guys to lose your face. If you don't read me, perhaps you guys need to ask some smarts, e. g., Bohica (short and quick) or Nick (if you have some time).

hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Mon June 21, 2010 at 9:38 PM by ice-n-tropics

bohica2xo on Mon June 21, 2010 10:10 PM User is offline

Bob:

With only Omega's page to work from, it is hard to say what size fuse is appropriate. There is no way to make the horsepower they claim on even the recommended 200a fuse.

The statement about NOT installing a contactor from Omega makes me think there is some sort of control circuit (pile of mosfets) under that rear cover. The nearly flat torque curve & constant 2000 rpm supports this theory.

Tex (Ice-n-Tropics) is closely tied to the compressor business, perhaps he can tell us how much horsepower the trash90 can soak up @ a fixed 2000 rpm. That will give a more complete answer on the current draw issues.

As for the "T" fitting, it is always a design issue. Oil return in dual (or very long) systems can be frustrating to say the least. Personally I favor the oil separator approach, I have had good luck on 40 foot motorhome systems with it. A couple of added parts, but the compressor goes the distance.

It does look like you may be short on capacity. The Omega chart says 10 to 15 k btu/h @ 2000 rpm. Tex says more that twice that is typical.

You had not mentioned the 40SI & isolators when I started typing that post. Plan right now for more alternator, or carry a spare. Two 40SI's can be mounted & sistered, perhaps even on top of each other with an idler or two...
The isolator will be a real nice 200w heat source, so keep it well ventilated.

Tying the 40 SI sensing circuit to one bank of batteries as most isolators do will work, but... The sensing wire should be tied to the cranking batteries. If it is tied to the badly depleted AGM's, it will cook the cranking batteries. A 125a charge rate to those 4 G31's will be fine. We do 450a on 12 G31's without issue.

If you plan to build more than one of these I would seriously look at going to 28v, or even the "42v" systems once proposed for passenger vehicles. Reduced current, smaller wire, etc. - since you plan to run everything off of the alternator. Delphi did a lot of work on 42v, but it got pushed aside with the 300v hybrid stuff. Plenty of that technology got all the way to a producible part. Even 28v would be an improvement.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Tue June 22, 2010 7:55 AM User is offline

I assume since this thread started off with a tee placement, this system hasn't even been run yet, we learned this is a diesel truck that already has bank of batteries just to start it, an electrical compressor replaced the conventional compressor that may place an additional 220 amp load on the system, and a bank of four more batteries have been added that in all probability will completely discharge that bank of four additional batteries.

Try repeating the above statement ten times in a role.



In terms of electrical loads on the alternator, the battery or many batteries in this case are the scavengers and will eat up everything left over that alternator can deliver. In a semi or complete discharge state, everything the alternator can deliver. An alternator is current limiting device, and it does this by limiting the strength of the magnetic field from the rotor, actually due to cost restrains, to the point where magnetic saturation has already been past further decreasing the efficiency of the alternator. And by choosing the wire size in the stator such that its impedance will cause internal voltage drops limiting the output voltage.

You can actually short the output of an alternator, or should be able to without hurting it. It will deliver its full output current, but into a short circuit, 0V times any current is 0 watts, so essentially its delivering 0 power. In this state, takes very little power to rotate the alternator.

For the typical alternator at rated voltage and current, it consumes just as much power as it can deliver, those suckers get hot, like 200*C hot. Good example of this was with the introduction of the CS-130 105 amp alternator that replaced the 63 amp 10SI, the former was smalled than the conservative designed 10SI, actually its key to higher output current was the installation of fans to keep it from turning red. To further conserve on cost, only 90 amp diodes were used and for the most part, would survive. A worse case scenario was a guy leaving his car at an airport for three weeks where all that standby current would drain the battery and discharge it approximately 50%. Angry after being treated like crap at the airport, starts his engine, switches on the AC forcing the radiator fans to turn on plus another 27 load from the blower, revs his engine to over 3,000 rpm to get the hell out of there, his half dead battery with an already 70 amp load on the system consumes the other remaining 35 amps, exceeds the diode rating, and the blow apart.

But hey, with the one year warranty, as long as more profit was shown by using the cheaper diodes as opposed to warranty cost, leave it, the bottom line is making money.

In the case of this 40ST, certainly would like to get my hands on it, retired now, with a rated output of 300 amps, a nominal truck load of 40 amps, an additional 220 amps to run that electric AC, that only leaves 40 amps left over to charge two large banks of batteries. Bohica makes a good point about adding a second alternator, will will need it. If diode isolation is used, the setpoint of the alternator will have to be increased to compensate for the diode drops or proper charge levels will never be maintained. But this can be compensated for someone if the alternator has an external voltage sense pin, but for which battery stack? Flip a coin.

Yet another factor in particular with trucks, a battle I could never win was the use of non-temperature compensated voltage regulators, a truck in Mexico would only need 13.3 volts to fully charge the batteries, but that same truck in a run up to Canada would need 15.5 V to fully charge the batteries that led to battery freezing and warranty repairs for the battery division. Hell with it, just leave it.

Realize that this post just started off by moving a tee for oil circulation problems that are developing into what I consider, major electrical problems as well. Feel you would solve both problems by sticking with the conventional system for the cab and just using the electrical for the sleeper. Like a window type unit with the fan blowing the hot air outside of the unit, a lever for recir or external air, and a thermostat, plus gaining an additional 200 amps to charge those batteries.

Batteries have another characteristic, they can discharge a hell of a lot more current without damage than what you can charge them with, and the charging rate is strictly determined by the output of the alternator. With an isolated alternator, if you used a 50 amp alternator would charge at a 50 amp rate, with a 300 alternator at a 300 amp rate, the later may well cook those batteries.

But lets see what happens after you fire it up.

ice-n-tropics on Tue June 22, 2010 10:17 AM User is offline

Pal 2xo,
After a trip around the Cape, Nick went on record that the electric powered comp should be used only for no-idle sleeper with belt drive for mobil mode. What say you?
Do you think that Bob's electric driven over the road comp is an acceptable application for a revolutionary optimum fuel mileage prototype Class 8 truck? Or does it need to be scrapped before it drags this project down into the scrap heap.
TR90 @ 2000 crpm = approx 2.7 KW depending on pressures.
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Tue June 22, 2010 at 10:19 AM by ice-n-tropics

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