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Author Topic: Power a coach with 2 - 4000 watt inverters  (Read 4911 times)
Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #15 on: May 16, 2006, 08:26:56 PM »

Yea Jerry,

I did, and they couldn't resolve it ! We don't live in a perfect world, Huh!

Nick-
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darrenayres
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« Reply #16 on: May 17, 2006, 04:57:50 AM »

Melbo,

I think I would have left my mother out of the hot tub! Wink

Wayne,

I used to drive a lot of Marathons with all that inverter power. Did a rock and roll gig with Neal Schon from Journey for 3 months back in 2000. The only advantage I saw to having lots of batteries and inverter power was when running the a/c in an underground parking garage. The other buses were not allowed to run their generators and create exhaust gases. I could run 2 rooftops off battery for almost 4 hours.

I don't imagine you'll have those issues.

Darren
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gumpy
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« Reply #17 on: May 17, 2006, 05:21:27 AM »

...
I could run 2 rooftops off battery for almost 4 hours.
...

Ok, I'll bite. Please give us some details of the size of the battery bank that would allow running 2 rooftops for 4 hours, because I'm thinking that's pretty much impossible without a whole busload of batteries.

Anyone care to run the numbers for a standard rooftop A/C load. I'd be curious to know just how many batteries would be needed to support this.

craig
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Craig Shepard
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Melbo
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« Reply #18 on: May 17, 2006, 07:30:37 AM »

Wow So Much to respond to here

darrenaryes

My mom is old enough to do what she wants but I understand your concern.

Nick

What did you do to keep the fam cool when the electric was a little low on spark?? HVAC equipment doesn't seem to work as well without electricity. I hope you didn't have to go low tech and give everyone their own bag of ice.

Gumpy

I'm with you I would like to know what the size the battery bank was but I will in darrenaryes defense guess that the coach was already cool when it went into the underground parking and because it was in underground parking was out of the sun -- ie -- in a cooler place than most so the compressors would not cycle as much as normal so you could maybe run longer than normal on your batteries but I would still like to know how large the bank was

Melbo
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« Reply #19 on: May 17, 2006, 08:06:20 AM »

Melbo, Hey! I'm not slighting your mom at all. I just know if I had my girlfriend and my mistress in the hot tub with me already, I might be a little reluctant to enjoy them with my mom watching!! Although she has seen me naked before, hmmmm? Never mind.

Size does matter, at least in this case. I'm not sure of the amperage but the batteries were about the size of the 8D and used some kind of gel. The house unit had six, if memory serves me correctly, and another two ran the chassis. Like Melbo said, it was a lot cooler underground than in the blistering sun. Otherwise, I'd have been screwed since my passenger liked the coach kept at 65 degrees. Going down the road, that was tough at times. Fortunately, most of our driving was done at night.

There is a lot in these coaches to hold the cool temps, as well: marble floors, granite countertops, etc. Also, very well insulated. What would one expect for a cool mill and a half? Wink
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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #20 on: May 17, 2006, 08:07:11 AM »

Melbo,

i unplugged at 1pm, ran the gen set until 6:30 pm.   Problem Solved!

I'm not one to Bi**h, I just solve problems and get on with my life!

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« Reply #21 on: May 17, 2006, 08:20:17 AM »

Wayne- I have a very simple electrical system on my bus.  First off, the bus is wired for straight 120v, so I only use one leg of the 50 amp plug (or 6,000 watts worth).  I can run two roof A/C's and have juice left over.  While I can't run everything, I haven't been crippled by the fact of only a true 50 amp.  The main advantage to this setup is that you never have to worry about balancing the load between the legs.  I have certain circuts on a 30 amp going through my inverter (plugs in bath, kitchen, rear bed for entertainment unit, microwave and toaster oven, front plug for TV and heater in bath).  I have to be a bit conservative not to fire everything up, but all that happens is that the circut breaker trips, and since my box is inside, no big deal.
As to the gen, since my bus is a transit, my gen is mounted next to the driver's seat like a front engine.  It is accesed from inside (I didn't want to cut the very beefy bumper that transits have to create a front drawer) and is silenced by 1" lead foam.  While it isn't as quiet as I'd like, it is tolerable.  When the A/C's are running, can't hear it.  Since the box is a tight fit, the air cleaner is remote with an intake muffler provided by Wrico (4 cylinder engines put out a very noticable intake hum that is probably the loudest part of the engine).  Also, the radiator is remote mounted to a belt driven squirrel cage blower with a 1/2hp two speed totally enclosed fan cooled motor.  Use high during the day, and low at night for quietness.  Then for ventalation through the box, I have an in line bathroom ventilator to push air through the box and exit out the back (use the bathroom ventilator since it is designed for wet situations-incase you run in the rain-it won't hurt it and has a drain to exhaust excess moisture).  The ventilator is on a rheostat also to slow it down at night for quiet.  And lastly have a removable 8ft exhaust stack when camping (exhaust exits under drivers window).  The only change I wish is that I could have mounted the whole box on air bags inside the baggage compartment (if I had one).  I have heard gens so quiet that you had to be right next to the bus to hear them.  Problem with some of our older bus converters, is they have hearing loss, so a noisy gen doesn't bother them.  In my opinion, there is no such thing as a too quiet generator.  If you need help in obtaining sound proofing and using available sound deadening plywood, call Dick Wright at Wrico International in Eugene, Or-he has it all! Good Luck, TomC
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« Reply #22 on: May 17, 2006, 01:31:15 PM »

Just for fun I pulled out my Trace manual and reread the technical info on battery sizing.  The general rule is:

(AC current) X (AC voltage) / (battery voltage) = DC Amps.

It recommends a factor of 1.2 for inverter inefficiency and a 50% battery cycle for optimum lifespans.  This may be different for gel cell batteries, but I don't know. 

So, let's plug is some numbers-----  I went out to the bus and turned on my Coleman rooftop and checked the numbers on the meter.   14 amps draw from my unit and 114 volts output for the inverter and 13.1 volts on my  system.   I pulled these numbers off the inverter screen from the "meters" menu.  Seems like some of the newer rooftops may draw only about 12 amps, therefore more efficient.  The less the better.

14amps  x 114volts / 13.1volts batteries X 1.2 inefficiency / 50% battery cycle times 2 airconditioners (your application)

{(14x114/13.1 x  1.2) / .50} x 2= 584.80 amp hours

584.8 amp hours times 4 hours = 2339.20 amp hours of batteries before a required recharge.  (This assumption is based on actual  meter numbers and my 2 Coleman air conditioners running for 4 hours.)  Most sizing assumptions use nominal 12 volts , 24 volts etc. and the Mfg electric load rating as your numbers to plug in for amp hour sizing. 

I have 8 GC-2 golf cart batteries at 210 amp hours each series connection times 4 parallel connections for a total of 840AH.
According to the book if you hook up 2 six volt 210AH batteries in series, you have 210 amp hours at 12 volts.  If you hook up four 210AH 6 volt batteries in series you have 210 amp hours at 24 volts.  Therefore, increasing the voltage decreases the amp hours needed, but does not decrease the number of batteries required.  The advantage of increased voltage does give you the ability to derate the size of the cables.  To do this at 12 volts would require 0000 cable or larger.   I believe the 4000 watt inverters are 24 volt, maybe even some are 48 volt. 

 I priced GC-2 batteries at Sam's last week for $49.95 ea plus exchange. 

I have a Trace SW2512 inverter merged with my Niehoff 400 amp alternator.  I can run the front AC off the inverter.  The old Niehoff can barely keep me in the plus range with this setup.  The 22' cable from the alternator to the inverter affords me about 1.2 voltage drop.  Add any other loads and the battery bank goes minus.  I can't do this at night with the bus  lights on.  Usually it's too warm for one AC anyway, so the genny is on and I run all three rooftops. 

If I misread my manual and did the math incorrectly, someone please jump in and post a correction.

Good luck,  David


« Last Edit: May 17, 2006, 02:48:50 PM by David Anderson » Logged
prevost82
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« Reply #23 on: May 17, 2006, 02:29:09 PM »

I run 2 DR 2412 (2400 watt @ 12V). I install 2 to balance the 2 leg but the primary reason was to charge the batteries back up with both legs...240 amp charge instead of 120 amp with 1 inverter.... so the generator runs for a shorter time.
Ron
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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #24 on: May 17, 2006, 03:11:16 PM »

David,

you are correct!

I also have a 840 amp hour Batt bank, My 2 15,000 H.P.s  draw 14 amps each, the Inverter is the RS 3000 12v with 180 amp 3 stage charger, all cables are 0000,

and less than 5 ft from inverter, inverter is set at 10.5 volts alarm, I get 20 min. of run time on the 2 H.P.s without engine assisting charge!

Unlike the 4024, The RS3000  feeds both legs of 115v to the panel, that enables me to run anything  I want to in my panel from the inverter or the gen/ land line.

When I plug in, the RS300 has a power sharing charger that automaticly switches to the leg with the least draw on it, helps when using appliances.

Getting to the point, while ideling, the bus engine would have to be reved up to keep in the plus on the batt bank,  Is this True?   [220a alt.]

I havn't checked to see the output into the batt bank at idle.

thanks-
Nick-
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« Reply #25 on: May 17, 2006, 06:38:30 PM »

Nick,

I checked my alternator output with a digital multimeter.  I get about 14.1 volts at the alternator terminal, about 13.9 on the load side of the house bank merge solenoid and about 13 +/-  22 feet down the line at the inverter terminal.   There isn't too much difference reved up or at idle.   That may be a characteristic of the 400 amp Niehoff alternator.  Yours may be different. 

Your system is cool that it draws the charge amps from the lesser loaded phase line.  I like that.  I installed ammeters on each phase of mine to balance the genny load.  I try to keep each phase within 10 amps when running the genny.   It has worked very well for me to do it that way. 

One thing I do notice is if I put the bus at high idle and click on the air conditioner, I hear the engine lug down some rpms.  That electric draw does take some engine horsepower.  As stated before, there is no free lunch.  I need all my 6v92 I have when climbing mountains, so the genny is running the AC's most of the time anyway.  I have found that it makes it easier for my wife to use the appliances, etc while on the road.  I don't have to worry about overloading anything when my genny is running. 

David
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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #26 on: May 17, 2006, 06:51:31 PM »

Thanks David,

I mostly run my gen set too. When I get some time I'll do the same volt test on my alt. You know, tis my season!

Nick-
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