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Author Topic: the real truth, the whole truth, and nothing but the truth about inverters...  (Read 9223 times)
HighTechRedneck
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« Reply #45 on: April 14, 2009, 10:27:32 PM »

That being said, you should remember that freezers do not run 100% duty cycle, either.  So the batteries are charging when the compressor cycles off, and vice-versa.

Good point.  But also keep in mind the operating environment.  It will be hot and the freezer doors opened often.   compressor duty cycle will be high.

On CB's multiple alternator idea, can two alternators charge one battery bank without their internal regulators freaking out?
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Sean
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« Reply #46 on: April 14, 2009, 10:53:25 PM »

On CB's multiple alternator idea, can two alternators charge one battery bank without their internal regulators freaking out?


Yes, "but"...

The "but" being that to run two alternators against a single bank, you really have two choices.  One is to set one regulator just a tad higher than the other; when the bank is depleted enough to demand the full current of both, the voltage will be below the lower set point, and both alternators will produce charging current.  When the bank's voltage comes back up close to set point, eventually rising above the lower set point, that alternator will stop charging, and the other, higher set-point alternator will continue.  Naturally, this method means one alternator always works more than the other.  This can be evened out by swapping the set points (or just the regulators, if they are external) periodically.

The other, better, method is to use externally regulated alternators, and purchase a multi-alternator regulator designed to do exactly this.  Such a regulator will call for charging from both alternators as needed.  Models are available from Xantrex, Balmar, Ample Power, Electrodyne, and others.

If you do neither of these, and try instead to run two independent alternators with exactly the same set point, things will mostly work, but the alternators will be constantly competing when voltage is near the setpoint, with a "ping-pong" effect of each alternator alternately cutting in and out of charging mode.  More stress on the alternator this way, and, if you have other things connected to the relay terminal of one of them, such as a tach or a no-charge light, you will see effects there, too.

-Sean
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Busted Knuckle
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« Reply #47 on: April 15, 2009, 06:06:23 AM »

Wow all this clowning around makes we wonder "when the F... did we get icecream?" Grin  BK  Grin



Sorry but "The Ringer" has been a popular movie choice on the bus lately for some reason.  And that is by far my favorite line in the movie, and seemed very appropriate in this situation!
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Busted Knuckle aka Bryce Gaston
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« Reply #48 on: April 15, 2009, 06:56:26 AM »


Quote
BTW, we Stanford alums have great respect for the MIT guys when it comes to technology -- nearly our equals  , and just down the street from Harvard, the "Stanford of the East"  -- but they don't know a damn thing about football.  FWIW.

 Gag me with a spoon   Concordia 71 FVCC 72 U of M 73-74,  80-85 education quality is what one makes of it

 Skip
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kyle4501
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« Reply #49 on: April 15, 2009, 07:21:30 AM »

Kyle,  while I admire Fred Tinseth and all he has done to post some of his wealth of experience on his web site, and I have recommended (and continue to recommend) both of these pages as good reading for anyone building RV electrical systems, they are not the be-all and end-all on the subject.
Didn't mean to imply they were the absolute gospel, but merely a good start. Seems to me it's a good idea to understand the basics before attempting to design a custom system. . . . . Fred does a good job in exposing the magnitude of the whole system & what else may be involved without getting too lost in the theory.

I thought the questions being asked were so remedial that without some background info, the answers wouldn't be understood.

Maybe it's just me, but it seems many look at inverters as power sources rather than 'power changers' & don't seem to understand how the whole system works & the innefficiencies involved, OR how little energy is in a battery when you're talking about these types of loads.


If it were me, I'd look into adding insulation to the chest freezers & using them as ice chests while on the road. Some large blocks of brine ice in them would help increase their thermal mass & lengthen usefall time away from the power pole. Product organization can minimize the time the freezer is open. Then all he has to do is plug in over night & refreeze the brine ice. The savings from the cost of the required inverter, battery, & alternator would require less sales before breaking even . . .
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Sean
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« Reply #50 on: April 15, 2009, 08:39:07 AM »

Gag me with a spoon 

Skip, that was intended to be a tongue-in-cheek response to the "MIT lecture" comment.  I guess if it has to be explained, it's not humorous.

-Sean
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HighTechRedneck
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« Reply #51 on: April 15, 2009, 08:41:05 AM »

... how little energy is in a battery when you're talking about these types of loads.


If it were me, I'd look into adding insulation to the chest freezers & using them as ice chests while on the road. Some large blocks of brine ice in them would help increase their thermal mass & lengthen usefall time away from the power pole. Product organization can minimize the time the freezer is open. Then all he has to do is plug in over night & refreeze the brine ice. The savings from the cost of the required inverter, battery, & alternator would require less sales before breaking even . . .

I couldn't agree more on both points Kyle.

On the freezer alternatives, even if he used dry ice, it would be cheaper than the inverter/battery bank needed to do such a thing.  

Beyond the equipment cost, even charging via alternator off the engine is not "free", all that heavily loaded idling is going to increase fuel consumption significantly I would think.  And I don't know for certain, but it seems that the extended periods of the lateral pull of a heavily loaded alternator at idle might even cause added wear to the crankshaft bearings, at least the front one.  I suppose if you could connect two of them as Sean outlined and mount them exactly opposite each other, that would remove that concern.
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Sean
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« Reply #52 on: April 15, 2009, 08:59:36 AM »

... how little energy is in a battery when you're talking about these types of loads.


If it were me, I'd look into adding insulation to the chest freezers & using them as ice chests while on the road. Some large blocks of brine ice in them would help increase their thermal mass & lengthen usefall time away from the power pole. Product organization can minimize the time the freezer is open. Then all he has to do is plug in over night & refreeze the brine ice. The savings from the cost of the required inverter, battery, & alternator would require less sales before breaking even . . .


I couldn't agree more on both points Kyle.
...


I actually agree with  you, and I would add that for efficiency, simplicity, and cost, if I needed to freeze stuff in a moving truck, I would use an engine-driven cold plate system.  But the thread topic was inverters, and I assume folks will open this thread to learn about inverters, not cold plates (or generators, for that matter).  I don't have the first clue about the economics or business model of an ice cream truck, so I'm not the one to tell him not to do it -- only how, and what it might cost (somewhere north of $3k, I'd figure, by the time you add up batteries, inverter, charger, cables, alternator, and whatever miscellaneous bits are needed for a complete installation).

I would hope that everyone visiting would find something to take away from this kind of thread, even if where it leads is for the OP to decide on a completely different strategy.

-Sean
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« Reply #53 on: April 15, 2009, 09:22:26 AM »


 Sean,

    It was taken in that vain...........
 Just don't always understand all the hoopla....Last time I bought from a ice cream vender rig it was as a boy
 in Spokane and he had a real cool Harley cop trike with the back converted as a cooler. Used dry ice to keep things
 cold all day.......pretty green in my book plus cool tricks with the dry ice Smiley

 Skip
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circusboy90210
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« Reply #54 on: April 15, 2009, 11:15:01 AM »

OK so where is a good place to get custom brackets for a second alternator fabricated?? also thinking of running this as a separate 24 volt system if possible to charge3 3 or4 deep cycle batteries that are not connected to anything but the devices to be powered. If 24 volt inverter prices prove to be inconvenient then I will roll with 12 volt alternator. seeing as a custom bracket is involved then this will open up possibility's for more alternator choices. I"m guessing grounding issues would limit me to a 12 volt alternator. thank you very much.
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Len Silva
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« Reply #55 on: April 15, 2009, 11:43:18 AM »

Well, first of all, I apologize for my snide remarks earlier. However, your subject line and initial question did invite some sarcastic responses.

That said, I also believe that a generator makes far more sense and would probably cost less that any inverter setup.

If you know people who are successfully using inverters for this purpose then I suggest that you check them out and let us know what you find.

I think the Honda 4000 watt liquid cooled RV generator would probably last 8-10,000 hours if you changed the oil every week.

If you are still locked in to inverters then I suggest you temporarily use a generator for a week and use a P3 Kill A Watt meter http://www.p3international.com/products/special/P4400/P4400-CE.html to monitor all your electrical use.
I would also install a hour meter on the main engine so you can see how many hours it is actually running in the course of a  normal work day.

Keep in mind your electrical load will be considerably higher in August than it is in April.

Once you have that data it should be easy to convert kilowatt hours to battery amp hours.

As to custom brackets, you will have to get the alternator first, figure out where you are going to mount it, then find a local fab shop to build something.  I would think the circus community must have lots of welder/fabricators around.

There is no grounding issue with a separate 24 volt system, in fact, I would recommend it. The only draw back is that all your 12 volt devices, exterior lights, music etc. will have to run off the main truck system.
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« Reply #56 on: April 15, 2009, 02:30:15 PM »

nobody is out running yet as far as trucks worth copying their technique.  Cry I"m also far away from any shows or show folk at the moment who would have resources to help me. I have also went swimming with a phone since I left the shows and all my contacts are erased. Cry so I''m on my own for now. Tongue Cool
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« Reply #57 on: April 15, 2009, 03:54:14 PM »

Hmmm!!! Guess no one knows where to get an inverter fixed just how to get icecream hot!!!
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rwc
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« Reply #58 on: April 15, 2009, 06:45:16 PM »

I think that the cohesive answer is you need one unless you don't and it should be Pure Sine Wave unless its not. Also it should charge your batteries unless you don't have any. When you do thjis the way you need to do it then you should get a generator just to make sure.
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JackConrad
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« Reply #59 on: April 16, 2009, 05:11:20 AM »

Hmmm!!! Guess no one knows where to get an inverter fixed just how to get icecream hot!!!

What part of the country are you located in?   I had our Marine Freedom 25 repairred at a place in Sarasota, Fl. I do not know if they will just sell parts. If you live along a coast, check some of the large marine electronics dealers. Thats is the type of place that repaired mine.  Jack
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