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Old 09-11-2014, 01:45 AM   #21
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Default Dual alternators, why or why not ....

Using a higher voltage like 24v in the E-Trek makes a lot of sense. Probably some diminishing benefits going higher to 36 or 48v. The efficiency of inverters improves at higher voltages. The telco battery backups I've seen run their inverters at 48v. Then you could use a DC-DC converter, they are fairly efficient and used in hybrid and electric vehicles


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Old 09-11-2014, 01:55 AM   #22
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Default Re: Dual alternators, why or why not ....

Quote:
Originally Posted by Boxster1971
Using a higher voltage like 24v in the E-Trek makes a lot of sense. Probably some diminishing benefits going higher to 36 or 48v. The efficiency of inverters improves at higher voltages. The telco battery backups I've seen run their inverters at 48v. Then you could use a 48 to 12v DC-DC converter, they are fairly efficient and used in hybrid and electric vehicles


- - Mike
2013 AS Interstate on 2012 MB Sprinter 3500 Long & Tall


i read although i cannot be sure(roadtrek does not tell) that the E-trek essentially has it's batterys divided as 2 sets of 4 making 2 at 24 volts
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Old 09-11-2014, 03:11 AM   #23
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Default Re: Dual alternators, why or why not ....

Indeed, they are pretty secretive about it. But I have to say, for my CS E-Trek, the system is working exactly as advertised.

However I'm still confused as to what is 6 volt, what is 12 volt, and what is 24 volt.
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Old 09-11-2014, 10:13 PM   #24
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Default Re: Dual alternators, why or why not ....

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Originally Posted by booster
There do appear to be several ways of doing the engine generator thing, but I think the second, dedicated, alternator is the best way once you want be output to the batteries for charging. I you are just looking at running the microwave, you can get a 200 amp separator, although doing it that way will give some of Marko's cons.

We have 375AH of wet cells, and they don't seem to want to charge at much over 100 amps, even when low, so the separator would handle it. If you had 400+AH of AGMs, you would probably easily pass the 200 amps when they were low, so then dedicated would be best I think.

If you ignore parasitic and efficiency losses, I think you could put together an interesting system with a dedicated second alternator. I am assuming no attempt to run the air conditioning off of the batteries for any real amount of time.

What if, and looking for comments and opinions

24v, or even 36 or 48 volt 2nd alternator at about 5000 watts feeding a matching voltage pure sine inverter of also 5000 watts. Output of the inverter to a transfer switch with shore power for the van 110 volt outlets and a shore charger of at least 200 amps, with ending current charging. Output of the charger to the 12 volt portions of the van and the batteries of 4-600AH.

This setup would give you some pretty slick things. You would have very high battery charging off of a real battery charger that could be much more sophisticated than the alternator is, saving the batteries from overcharge while driving. You would have lots of 110v available without battery drain while driving. You would have the capability to charge very fast off shore power if enough amperage was available. If not, a good charger will have a reduced charge rate available to use, I think. If you wanted to have a reasonable amount of 110v power when not running the engine or on shore power, you would need a second, probably much smaller 12v inverter for that. 1500 watts would run most of the stuff, including the microwave, for reasonable amount of time. Solar would be normal as you would hook up to 12v batteries like you do now.

Benefits would come from low current to the inverter do to high alternator voltage. You would always be using the large and high quality battery charger, except for solar (unless you did a high voltage solar and also went through the inverter), which would be very good for you batteries. You wouldn't have to worry about having a disconnect on the second alternator when driving with full batteries, as the charger will go to float.

Downside would include losses from inverting everything and ????

Might work.
Some thoughts:

I wonder if 3600 watts would be enough. Just like a full 30A hookup.
Can the alternator work without a battery? (just bringing forward one of your questions from earlier)
Hard to find 200 amp chargers ---- maybe here: http://www.amplepower.com/products/chrg/index.html
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Old 09-12-2014, 01:48 AM   #25
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Default Re: Dual alternators, why or why not ....

I think 3600 watts would be plenty for almost all uses, unless you did have the 200 amp charger, low batteries, and were running the microwave or something else that used big Not likely to happen, I would think.

I think most of the good chargers can be paralleled , so you might need to do that to get the higher charge rates. I really don't know anything about really high rate battery charging, so maybe 100 or 150 amps would be plenty and better for the batteries.

I think that Sterling makes a 200 amp remote regulator that claims multistage charging, with variable timing, which might also be a possibility, if you didn't want to go to big charger off the inverter. If it got to float easily, or manually, you wouldn't need the disconnect on it.

So another system could be 200 amp alternator with 3 step regulator, 3600 watt inverter, 100 amp charger, 400-600AH of AGMs, and 300-600 watts of solar? All run off the second alternator.
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