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Topic: Alternator Talk (Read 569 times) previous topic - next topic

Alternator Talk

I was wondering with all the talk about alternators. What would be the downfall to having 2 alterators  or having one with an external adjustable voltage regulator. 

bf91425c.mp4 Video by RHoughton1 | Photobucket
1998 Foretravel U320c
4200 RCFE  unit # G5341

Re: Alternator Talk

Reply #1 –
One alternator, whether OE or higher output with smart regulator would certainly be easier and less expensive.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Alternator Talk

Reply #2 –
Quote from: wolfe10 –
One alternator, whether OE or higher output with smart regulator would certainly be easier and less expensive.

However, redundancy would certainly be nice. From what I've read it sounds as if many (perhaps most) of the coaches produced for the charter industry have dual alternators.

I believe they also operate most of their high-current systems at 28 volts (two 12 volt batteries in series) with a separate battery equalizer to provide 12 volts for those systems needing it. Certainly would be a nice--although expensive--system.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Alternator Talk

Reply #3 –
The percentage of mechanical diesels in motorhomes drops each day as environmental rules and technological advances have made the older engines obsolete. In many mechanical diesels, electricity is required to keep the fuel solenoid open and fuel flowing to the engine (poor thinking IMO). So, if the alternator fails, unless you start the generator, the engine will shut down after a few hours or less if traveling at night.

The choices for a second alternator location are excellent with our diesels. With our U300, we don't use the dash air so the compressor location could be used to mount one. Detroit owners could then install the block heater where it was intended to go in the first place and then just use a spacer to move the alternator bracket an inch or so away from the engine block. Some have already done this.

I am going to change radiator location on our U300 and get rid of the hydraulic pump and all the related motors, etc. This would be a perfect location for an alternator with the engine batteries only a couple of feet away.

Having a second alternator also means you can get rid of the isolator and while adding an alternator does increase the complexity in some ways, removing the isolator will greatly simplify the electrical system. This would create two separate systems with the ability to tie them together in the case of failure of one alternator by a something like a knife switch or latching relay.

Both alternators could be identical with another kept in a box for longer trip. The lower capacity alternators are easily found on ebay and two (or three) alternators are together, less expensive than one high output alternator. Also, easier to find if one goes bad.

The voltage on many alternators can be easily lowered to reflect the absence of the isolator. Adjustment is right on the top in our case with only a voltmeter and a screwdriver needed to do it.

For a DIYer, the cost would not be too much over $100, $200 max if you can source your own mounting hardware and cables.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Alternator Talk

Reply #4 –
I would just eliminate the isolator and put full power into the house bank with a zero voltage drop relay based isolator charging the start batteries. Which is basically what I have right now, since my isolator was burnt up I just moved the alternator output wire to the house bank terminal and connected them to the start batteries with a Yandina Combiner 100. Anytime the alt or inverter is charging, the house and start batteries receive a full charge. Instant starts all the time, and no risk of running the start batteries dead while boondocking. It doesnt combine until voltages rise above 13.0-13.2, so the house batteries get a good charge before it starts charging the starts.
Matt
95 U300, 78k miles
Cat 3176 Jake Brake, HD4060.

Re: Alternator Talk

Reply #5 –
Quote from: Pierce & Gaylie Stewart –
The percentage of mechanical diesels in motorhomes drops each day as environmental rules and technological advances have made the older engines obsolete. In many mechanical diesels, electricity is required to keep the fuel solenoid open and fuel flowing to the engine (poor thinking IMO). So, if the alternator fails, unless you start the generator, the engine will shut down after a few hours or less if traveling at night.

And a electronic engine has a computer, injectors, solenoids, often fuel pumps, and other stuff that all run on electricity. I'd say a mechanical would run much longer than a electronic engine with a failed alternator.
1998 U270 34'

Re: Alternator Talk

Reply #6 –
I work at a semi truck salvage yard and can come up with a second alt. for next to nothing.  and building a second bracket would be no problem. Its just hard on an alternator to charge a set of dead batteries. As most alternators are not rated at a 100% duty cycle so dry camping would put a load on the single alt trying to charge house batteries. and the idea of having a back up would be a cheap insurance policy.
1998 Foretravel U320c
4200 RCFE  unit # G5341
 

Re: Alternator Talk

Reply #7 –
Since I eschew (gee, I've always wanted to use that word) driving at night I'm going to rely on my solar panels and my generator to provide secondary (and tertiary - hey, that's two good words!) backup.

In fact, I'm wondering whether it might not be a good idea to simply stop using the alternator while driving during a sunny day. The solar panels provide more than enough power for what my 1993 mechanical Cummins 5.9 needs. I wonder if my fuel consumption per mile might not improve.

Plus my solar charger (a classic 150 - which is rapidly becoming the standard) is far safer for the batteries life than the alternator is anyway. I have been using it exclusively for house battery charging (except for the odd week of really cloudy weather). I keep the "salesman switch" off and watch the TriMetric closely every day and everything looks nicely charged. I have a battery maintainer on the engine bank but I am seriously looking at a latching relay for the "boost" function; or just a wire between the banks (which would mess up the TriMetric's overall kwh calculations since that bank has an unmeasured ground).

I do have 50-amp shore power but that only runs the clock on the microwave and the oil-filled radiator-type heater. Plus the engine bank's battery maintainer.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."