Sounds pretty good in theory, but in practice, you never get something for nothing. It takes horsepower to push that truck through the air.

It also takes horsepower to haul weight (batteries) and horsepower to turn an alternator. There is no such thing as free lunch.

Take any old GM three wire alternator and apply 12 volts to the field windings. Now see if you can turn that pulley by hand... nope... not in a million years. Now attach that alternator to an engine an do the same thing while the vehicle is idling. If the belt is real tight, the pulley will still turn, but the drag on the engine will be very noticeable.

Ever notice, on a car with a computer controlled idle, how the idle drops momentarily, then speeds up as the computer compensates for a heavy electrical load. This is because the throttle had to be opened to maintain the same idle when the alternator placed a bigger strain on the engine.

In the real world, the amount of energy expended would be greater than the energy generated due to frictional and heat losses.

Understood.
...And the reason why I suggested a special regulator that could monitor alternator rpm & adjust the max charging current (field current) to keep the alternator turning.

Also, why I suggested a small alternator so it didn't require a lot of wind to move it.

When I think about it, the charging current only has to be in the 10's of amperes to charge a few batterys over a period of a few hours on the road.

My biggest question is why not just allow the truck alternator to charge the battery(s) in the first place? Just install a slightly larger alternator and be done with it.

I'm just doing some calculations using the tiny little window air conditioner sitting in my kitchen window. It's about 5500 BTU's and draws 4.7 amps at 120 volts or 564 watts.

564 watts divided by the typical 24 volt truck system equals 23.5 amps. So to run this tiny little unit on batteries for 10 hours would require 235ah of battery power. I would think most 4 battery systems on trucks could handle this amount of current drain. Heck, two 12 volt deep cycles should be able to power it.

A couple of separate deep cycle batteries on the truck wouldn't add all that much weight. Throw another alternator on the engine to keep them charged separate from the truck system. Even this window unit itself could be used in a truck without modification. It could be mounted under the bunk with the condenser vented between the sleeper and the trailer.

Obviously company drivers can't try this... but if you own an old beater, why not?

There's a couple minor flaws in your thinking.

The start-up curent for that unit would be near double the average draw for a couple seconds or so.

Most inverters run off 12.6-13.8 vdc.
You can probably find one that runs on 24vdc in a custom electronics shop or rv center.

If you have to run it on 12.6vdc, the current will be double.

Plus, in either the 13 or 24vdc case, there's a inefficiency in the inverter of about 20-30% so you need to add that much more current to the equation.

600 watts/24vdc=25 amps + 5 amps(20%)=30 amps constant.

600 watts/12.6vdc=47.5 amps + 9.5 amp(20%)=57 amps constant.

Then you need to find an inverter to handle that kind of duty cycle & a set of batterys to run it for a few hrs straight.

I was really only roughing out the calculation for how many batteries you'd need to run the unit constantly for 10 hours. Four decent quality deep cycle batteries would provide twice the required AH rating. And yes, you'd have to deal with momentary surge current draw as the compressor switched on--mainly an inverter issue, which I didn't address.

My dad's motorhome has two rooftop AC units. I'm not sure how many BTU's they are, but he can run one of them for quite some time off an inverter and the 'house' battery.

Now as for the inverter, I had a 600 watt (continuous) 1000w (surge) true sine wave inverter that I used to run in my truck, way back before most truck drivers even thought about having 110 in a truck. I remember paying about $700 for it.

I just searched for a 600w sine wave inverter and found a couple 24vdc units that are around $270-330... a hell of a lot cheaper than they used to be! Back then (early 90's), you couldn't even touch a 600W square wave for $300.

Anyway, if you're pretty handy with mechanical and electrical things, battery powered AC could be had for probably less than a grand.

Those of you truckers looking to stay cool this summer without wasting fuel I think I have the answer for you. Why not try a 12 volt Air Conditioner. All you need is some ice and 12 volt outlet.

Available today at [LINK POSTED BY MEMBER] Only Members Can View This Truck Forum Link.

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Here's a question I've always had. Federal Osha Regulation states that the employer must provide a safe and comfortable working environment. If that is so, does that apply to truckers? If so, every single law passed for anti-idling is against federal law.

The problem with many of the Fedral laws is States pass contradictory laws and there is no way to enforce them. Thus most laws are enforced on a select basis, usually the one tat will bring the most revenue to the government.

To get this settled would require a costly lawsuit and, in reality, probably will never happen. However it is nice to dream.

In my opinion we need to go at this from a safty rather than a comfort standpoint. Contact the State, Federal Dots along with the respective OSHA agencies, our congessmen and senators (both state and federal) and explain the safety issues involved. Historicaly the agencies and the courts will rule on the side of safety...

hobo

I took a look at that unit on the website.
It reads like a swamp cooler.
These work by evaporating moisture into the air.
Your body then has a layer of moisture on it to evaporate without effort.
A true A/C unit takes the moisture out of the air using a coolant.
It's Ok in places where the ambient humidity is very low but worthless elsewhere.
That would only work in places like Nevada <which is where I lived> where the usual humidty is only 20-30% much of the year.

I am going to look into those battery operated AC systems.


What is an HIT tank?

I hope you have screens for your truck windows if you are sleeping with them open!



Looked good until I read about the moisture.

I hope no no dies of heat exhaustion!!! SAFETY! D@m Right!


O.K. So I've been checking out these "PORTABLE" air conditioners, and noticed there are many different models. Some going on sale at Costco forapprox. $300 to $600 The first thing I noticed was the size. Obviously these are probably going to be too big. BUT, if there was a model say, the size of a dorm fridge and you could run it on an inverter, wouldn't that be doable?

I found some small generators for camping etc and wondered how quiet they were and how much fuel they'd use, and if they could be bolted down on the back of the truck somewhere.

I was thinking we need a small generator anyway because of the fridge. I don't think he's keeping his fridge cold enough. He doesn't idle much. I know that will look different soon! He has ice for overnight but...


Why can't the reefers have a hose connection going to the cab for cold air?

Hey baack, I hope you find your statistics somewhere!

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