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Old 07-19-2013, 02:30 PM   #1
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Default Under the hood generators, dual alternators etc.......

I thought it would be useful to have a new topic that shows the many under-the-hood options available to use to generate power in an RV. I previously posted the four units in the E-Trek topic:

Mobile Electric Power Solution, Inc. (MEPS) - http://www.meps.com/products.html



Aura Systems Inc - http://www.aurasystems.com/pages/prod_intro.html



Raven Technology - http://raventechpower.com/



Fabco Power - http://www.fabcopower.com/generat/bgen.htm



and here are a few more options:

American Power Systems - http://www.americanpowerinc.com/sprinte ... rnator.htm
Alternator 3600 watts rated power. PDF file: http://www.americanpowerinc.com/images/ ... %20amp.pdf



Nations Starter and Alternator - http://www.nationsautoelectric.com/bosch.html



and here's a photo of a second alternator installed in a Sprinter



Mechman Alternators look interesting - http://store.mechmanhighoutputalternato ... ternators/



For my van, it looks like I could get 270+ amps at cruising speed or 165+ amps at actual idle speed for around $500 or 370+ amps at cruising speed and 200+ amps at actual idle speed for around $800.

370 amps x 14 volts = 5,180 watts ! ! !

Couple one of the high output alternators to a suitable sized inverter and you'll have lot of power
Attached Images
File Type: jpg MEPS Mobile Electric Power Solutions.JPG (31.7 KB, 2314 views)
File Type: jpg Auragen Aura Systems.JPG (48.7 KB, 2312 views)
File Type: jpg raven under the hood.jpg (109.7 KB, 2310 views)
File Type: jpg power-mite .jpg (44.1 KB, 2309 views)
File Type: jpg American Power Systems high output alternator Sprinter.jpg (27.8 KB, 2312 views)
File Type: jpg Nations Auto Electric 280 amp.JPG (46.8 KB, 2315 views)
File Type: jpg 2nd alternator installed in a Sprinter-DAK-270XP-3.jpg (132.7 KB, 2324 views)
File Type: jpg mechman alternator.jpg (50.4 KB, 2312 views)
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Old 07-19-2013, 02:47 PM   #2
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Default Re: Under the hood generators, dual alternators etc.......

Almost forgot - here's a PDF file from Sprinter Engineering and Compliance Support Team showing how and where to attach an aux alternator on the right side of the engine next to the oil pan. Download link: Sprinter Auxiliary Drive Retrofit (Diesel only)
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Old 07-19-2013, 05:33 PM   #3
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Default Re: Under the hood generators, dual alternators etc.......

Anything out there for those of us stuck with GM/Ford/Chrysler gasoline engines?
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Old 07-19-2013, 09:39 PM   #4
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Default Re: Under the hood generators, dual alternators etc.......

I now believe the E-Trek is using a Nations 280 amp unit which was mentioned previously by markopolo as a possible contender. The use of the word generator is I believe for marketing reasons since people want to know where is the generator. When told it is under the hood they are satisfied.
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Old 07-20-2013, 01:52 AM   #5
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Default Re: Under the hood generators, dual alternators etc.......

Quote:
Originally Posted by Mike
Anything out there for those of us stuck with GM/Ford/Chrysler gasoline engines?
I haven't looked for any detailed install docs for GM/Chevy, Dodge and Ford but I think there are products for those vans at the links above. The Mecman alternator I spec'd was for my GMC Savana Van.

Quote:
Originally Posted by pattonsr
I now believe the E-Trek is using a Nations 280 amp unit which was mentioned previously by markopolo as a possible contender. The use of the word generator is I believe for marketing reasons since people want to know where is the generator. When told it is under the hood they are satisfied.
Like you, I'm thinking that they could be doing it with two alternators. Maybe combining the output from the two to get to the reported wattage of 3500 at idle and 5500 cruising.

Imagine having two of the Nations high amp alternators. Combined 400 amps at idle and 560 amps on the highway. 400 amps at 14 volts is 5600 watts..... at idle!

For a DIY van or upgrade to a converted van a single $500 Mechman alternator with 165+ amps at idle (in place of the OEM alternator) could be enough to run a Class B sized air conditioner or quickly charge a battery bank. You'd need suitable sized wiring and isolator or separator.
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Old 07-20-2013, 02:23 AM   #6
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Default Re: Under the hood generators, dual alternators etc.......

It is interesting that the focus seems to be on generating 12volt power from the engine. I think it would be so much more efficient, in so many ways, to generate 120volt AC power. The only downside I could see would be that you would have 120volts under the hood, which is unusual, and could be a hazard.

Just the air conditioning will take about 100 amps at 12volts

Microwave maybe 75?

Fast charge batteries 100 amps

You would need much larger cables than starter cables because the need to carry the load continuously and need to not heat up. Maybe 4-0. A single 8-10 gauge wire could carry that much wattage as 120v AC.

I would just make sense to generate the 120v, use it for the 120volt uses as is, and convert it for battery charging, at the converter, with a much shorter, smaller cable. Alternators make AC power and change it to DC anyway, why keep changing it back and forth? What am I missing here?

The other thing to consider is that the big, big alternators I have seen rarely put out rated power in actual use, especially over longer periods of time. As they heat up from the large output, they lose efficiency quite quickly, so a 250amp alternator may only be 200 when it is running full out and hot. This is especially true on a vehicle that isn't moving, as you have much less cool air through the engine compartment. Things can get really hot while sitting still.

I think I just answered my own question, you would need a frequency converter to generate AC off of a variable rpm source to get anything resembling 60 cycle power.
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Old 07-20-2013, 05:27 AM   #7
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Default Re: Under the hood generators, dual alternators etc.......

The MEPS system inverts the DC to a pure sine AC that solves the variable rpm source problem. This system seems best for TV vans that do not have a large battery bank nor inverter/charger.

So it may be best to just use a second high amp alternator to feed DC straight to the house batteries. And then use a large inverter to provide pure sine AC to everything including the A/C. Of course, a large battery bank and a large inverter work best. I believe this describes the E-Trek package.

I still do not understand how driving all day feeding DC to AGM batteries does not result in overcharging the AGM batteries. Let's assume that one is on shore power and the batteries are close to being fully charged. What is the second high amp alternator doing to the AGM bank if I leave camp and drive for 10 hours?
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Old 07-20-2013, 12:46 PM   #8
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Default Re: Under the hood generators, dual alternators etc.......

Quote:
Originally Posted by pattonsr
The MEPS system inverts the DC to a pure sine AC that solves the variable rpm source problem. This system seems best for TV vans that do not have a large battery bank nor inverter/charger.

So it may be best to just use a second high amp alternator to feed DC straight to the house batteries. And then use a large inverter to provide pure sine AC to everything including the A/C. Of course, a large battery bank and a large inverter work best. I believe this describes the E-Trek package.

I still do not understand how driving all day feeding DC to AGM batteries does not result in overcharging the AGM batteries. Let's assume that one is on shore power and the batteries are close to being fully charged. What is the second high amp alternator doing to the AGM bank if I leave camp and drive for 10 hours?
If the MEPS system is putting out DC, as it appears, they are smart to invert it right away to make it easy to move in smaller wires. I wouldn't be surprised that running it to the batteries as AC and using a good 3 step charger would be a good option to save them. High current availability won't kill the batteries, so the size of the alternator doesn't matter, only the output voltage. We have found long drives on full batteries to be hard on our batteries, as our Chevy ran at 14.4-14.5 volts going down the road. Our wet cells would need water every 2500 miles or so, even if it was only a few days. We changed the regulator in the alternator to get it down to 13.9 volts and have been fine since.

So I guess my revised ideal system would be a very high amperage DC generator with very short wiring to the pure sign wave inverter, and then AC to all the AC stuff and a separate converter to charge the batteries.

In our case, it does get to be kind of an exercise in neat stuff, though, and nothing we would ever buy, I think. Since I would never consider using the van engine as a generator to run the air conditioning, the biggest load goes away. That is probably over 1/2 of the increased output needed if you left it in. An extra 180 amp alternator would supply plenty of 12v power for the other things and could be regulated to charge at the correct voltage. Running the van engine to use the microwave would be fine for me, and you would still get the battery fast fill up when needed.
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Old 07-20-2013, 10:11 PM   #9
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Default Re: Under the hood generators, dual alternators etc.......

Great points mentioned - thanks.

I did some testing today and it looks like a new high amp output alternator would be beneficial in my van. It's not a necessity so I don't know if I'll spend the $$$ to do it though.

My 1997 van has a stock 124 amp alternator. I'm pretty sure it is a CS144 type and is the alternator that came with the van so it's 16 years old.
My 600 watt microwave oven power consumption rating is 900 watts. It draws 90 amps DC when run through my 1000 watt inverter. The inverter display actually shows 970 watts when I run the microwave oven so it is maxed out.

I previously installed a switch on the dash to allow me to choose from 3 different idle RPM speeds, 624, 1070 or 1360.

Fuel consumption noted on my ScanGauge today:
624 RPM .10 GPH
1,070 RPM .22 GPH
1,360 RPM .31 GPH

The test was to run the microwave with the engine running at the three different idle speeds to see the affect on voltage. I combined the 2 house batteries, the 2 chassis batteries (4 batteries total) and the alternator for the test.

The voltage quickly dropped to 12.9 volts at each RPM setting. Each time I tested I ran the microwave for 20 seconds and I tested it 2 or 3 times at each RPM setting. The voltage recovered right away but was a little lower after each test. From 14.4v at the beginning down to 14v by the end.

I expected the voltage drop to be different at the various RPM setting - anyone know why it was the same each time?
Anyone care to speculate why the voltage didn't recover to 14.4v right away?

When I ran the microwave on only the 2 chassis batteries with the engine running the voltage dropped to 12.3 volts. Again, it was the same result at each RPM setting.

Ideally, I'd like to see much less of a voltage drop with that very large 90 amp load. My guess is that I'd need an alternator that outputs 140 amps or more at idle to maintain 14 volts while running the microwave. What do you think?
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Old 07-21-2013, 12:13 AM   #10
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Default Re: Under the hood generators, dual alternators etc.......

I think I remember Sportsmobile offering one of the above as an option, coupled with a transfer switch. The advantage of this would be that when going down the road, one could have the rooftop A/C and the dash A/C on (which is a must here in Texas). Then, when parked, flip the diesel generator on and one wouldn't have to run the engine for long hours idle.
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