Thank you Matt, Jim, Ken, and Bruce,
I am getting quite the education on alternators and the 12 volt power system.
Appreciate the help.
Gary Coaster / Reno, NV
1977 GMC Eleganza ll
GMC RV Day Night Shade Sales
GMCShades
www.GMCMotorhomemarketplace.com/GMC_Shades/
>
> I am with Matt 100%. 1 wire alternators might work OK in hot rod
> applications, but they lack the ability to fully charge a multi-battery
> system like is present on GMC coaches, Offshore Boats, etc. You really need
> what is called a "load excited" controller on the alternator.
> Yes, there is a .7 volt DC drop on the two output lugs on the
> isolator. Fact of life. Nature of diodes. But, the center input lug has
> full alternator output. Then we get into electromotive force. That is more
> commonly referred to as voltage. So, in an "IDEAL WORLD" a wet cell has 2.2
> volts fully charged. Multiply that times the number of cells, in this case
> 6, and you have 13.2 volts. Combine that voltage with the total resistance
> in the circuit, and that becomes the force which must be overcome in order
> to move electrons from a charging source to a storage source (wet cell
> battery). So we call that force, "counter electromotive force" . Probably
> in the real world, somewhere around 14 volts or a bit higher than that.
> That is with a slightly discharged battery.
> The 1 wire alternator will never, ever get that battery to an ideal
> state of charge. Just the facts of the case.
> Jim Hupy
> Salem, Oregon
>
>>
>> Response to Bruce, Gary and KenH recent posts.
>>
>> I hope you have read all three posts because I will refer to all as I go.
>>
>> It is very rare that I feel I have to add to posts by Bruce, KenH or KenB,
>> but here I feel I should.
>>
>> Because of the boat work that I have done, I have an unusual amount of
>> 12VDC systems experience and a lot of it is paid work making what other
>> people
>> modified actually work as it should. This means that I have seen and
>> corrected an assortment of PO and CO misapplications (what we would
>> recognize as
>> screw-ups).
>>
>> For a starting point, you must understand that a lead/acid battery has a
>> life that only exists between 11.9 and 12.7 Volts (some may argue the at the
>> 0.1s). If the plan is to recover two separate and different banks to
>> 100%SOC, the game gets interesting. The narrow window for the battery
>> chemistry
>> just makes it more interesting and problematic. It can be accomplished,
>> but due care must be taken.
>>
>> Isolators and combiners are just the start, but a very good start.
>>
>> If you have a single wire alternator, an isolator is a lost cause. The
>> 0.7V junction drop of the diodes will prevent ever getting the either bank
>> to
>> charge to full density (100% SOC). Recent Delco alternators are all
>> designed to output at about 14.5V. It takes 14.4V over a considerable time
>> to
>> get a battery back to full density. With a single wire version of a 27SI
>> Delco going to an isolator, you are going to max out at about 13.6 (with the
>> included wire losses). Well, gee, a continues battery tender is often
>> 13.4 and it won't actually charge anything.....
>>
>> So, if you have a single wire and an isolator, you will be at an immediate
>> disadvantage as you will have only about 80% of the bank or battery
>> capacity available. If you add a combiner across the battery terminals of
>> the isolator, you still won't do any better.
>>
>> If you have a single wire alternator, I suggest that you:
>> A - Buy and install a 100+Amp combiner across the battery terminals of the
>> isolator and
>> B - Move the alternator output lead to the coach (main engine) battery
>> side of the isolator.
>> This way if the combiner fails to combine, you will at least still have a
>> running main engine.
>>
>> If you are playing this game, I would also suggest that you get volt
>> meters (3-1/2 digit digital are cheap enough) for at least the main engine
>> battery (a Digipanel works but it is short resolution). If you have a
>> real (Bogart or Victron?) you can just pay attention there.
>>
>> Special note to Gary**
>> If your coach is approaching 100K, the starter can probably use a
>> refresh. It is my carefully considered opinion that the 10MT starter is
>> actually
>> too robust (too well made). I have seen these things stay in game when
>> they should have quit a while ago. When they do go out, their is no quick
>> recovery as they are seriously gone.... Unfortunately, as they are
>> finally giving up (that they do with great reluctance) they behave just
>> like a bad
>> power connection. So, yes, as you said you might, find an auto electric
>> shop that has a guy that still does this crack it open.
>>
>> Matt
>> --
>> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
>> GMCES
>> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
>> Brakes with Applied Control Arms
>> SE Michigan - Near DTW - Twixt A2 and Detroit
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