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| Re: Increasing the size of alternator power feed wire? [message #365173 is a reply to message #365171] |
Fri, 02 July 2021 08:21   |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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The stock size of #10 provides some protection to the alternator from high currents, especially spikes. If you add a heavier wire, then you will likely need to install a higher current rated alternator and isolator.
The OEM 3 wire alternator has a remote voltage feed-back circuit which compensates for the voltage drop in the alternator output wire and the isolator, so worries about those voltage drops are not an issue.
If you have a large battery bank for the house, you may want to look at a DC-DC charger for the house bank. It will limit the maximum charge current when the batteries are low and charge the house batteries with the proper current/voltage for the battery chemistry, just like a "Smart Charger".
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: Increasing the size of alternator power feed wire? [message #365177 is a reply to message #365171] |
Fri, 02 July 2021 08:53 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Great explanation. It’s an engineered “spring cushion” allowing the alternator to put out a higher Voltage but still maintain correct system Voltage trim. Any Voltage drop before the horn relay stud junction point is automatically made up by the remote sense to the Voltage regulator. So increasing the alternator output wire gauge is not a good idea as you are defeating the engineering. Furthermore, if you increase that wire gauge, the Alternator will get hotter as more Amp draw. This will lower your Voltage as the internal regulator is also “smart” temperature compensating to match the temp/Voltage curve that the batteries should see. This will falsely lower the output to try to not overheat the batteries. This will only be a couple tenths of a Volt drop to compensate for temp, but in terms of battery charging, a few tenths is HUGE! Also Hi blower will be slower, slightly.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Fri, 02 July 2021 08:57] Report message to a moderator |
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| [GMCnet] Re: Increasing the size of alternator power feed wire? [message #365179 is a reply to message #365171] |
Fri, 02 July 2021 08:31 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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The primary fusible link is a number 16 ga black. DO NOT go to a larger size! GMC designed safety into their electrical systems. The 16 gauge is the weir size that has a fuse rating.
What is a fusible link:
A fusible link acts much like a fuse; only it’s designed to handle a different type of potentially hazardous scenario. These links are actually strands of wire wrapped in a fireproof covering and are thinner (smaller gauge) than the wiring harnesses they’re connected to. They are placed in-line between delicate harnesses and large electrical current sources in your car—between the battery and alternator, for example.
These links must transmit high-current electricity and protect the rest of the electrical system from dangerous spikes that could cause a fire. If there’s a surge, the link actually melts, as its resistance to heat is lower than that of the circuits it’s protecting. This cuts off power while protecting the engine bay from a fire, thanks to its fireproof wrapping.
Unlike a regular fuse they are not instantaneous but heat up before failure.
The NAPA # is BEL 784695 and retails for $4.09 US and you should be able to find it at any good autoparts store in CA.
J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan
> On Jul 2, 2021, at 8:35 AM, wrote:
>
> Anyone increase the size of the altermator power feed wire? The stock one on my coach appears pretty small for the job.....
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
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| [GMCnet] Re: Increasing the size of alternator power feed wire? [message #365181 is a reply to message #365173] |
Fri, 02 July 2021 08:34 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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P.S, If it is constantly failing Then you must go9 and find the root of your problems. Going bigger just creates more smoke!!!!
J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan
> On Jul 2, 2021, at 9:21 AM, Bruce Hislop wrote:
>
> The stock size of #10 provides some protection to the alternator from high currents, especially spikes. If you add a heavier wire, then you will
> likely need to install a higher current rated alternator and isolator.
>
> The OEM 3 wire alternator has a remote voltage feed-back circuit which compensates for the voltage drop in the alternator output wire and the
> isolator, so worries about those voltage drops are not an issue.
>
> If you have a large battery bank for the house, you may want to look at a DC-DC charger for the house bank. It will limit the maximum charge current
> when the batteries are low and charge the house batteries with the proper current/voltage for the battery chemistry, just like a "Smart Charger".
>
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: Increasing the size of alternator power feed wire? [message #365198 is a reply to message #365171] |
Fri, 02 July 2021 12:40 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Right I did not restate a stock 80A alternator in my answer.because a larger alternator was not included in the original post. Stock system is balanced system. Go to a 100A alt and balance is upset. Especially the isolator. You blow open the engine side diode and voltage will go sky high to house side.
John Lebetski
Woodstock, IL
77 Eleganza II
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| [GMCnet] Re: Increasing the size of alternator power feed wire? [message #365206 is a reply to message #365198] |
Fri, 02 July 2021 17:11 |
Kenneth Doyle
Messages: 9
Registered: September 2020
Karma: 0
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Junior Member |
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I'm contemplating a battery to battery charger to the house bank. The
primary purpose is to run a continous oxygen concentrator while traveling,
vs a small portable pulse concentrator. Concentrator pulls 275 watts max,
but is usually only pulling 100 watts.
I believe my coach has a 100 amp alternator, which is prone to crapping out
if the dash AC is run full blast. Would the 80amp be a better option if the
alternator dies again?
Will the batter to battery charger just replace the isolator?
Does anyone have a similar set up; i.e., battery to battery charger,
lithium battery, inverter? I have tentatively decided to use a Battle Born
battery, Victron Orion Tr Smart 30amp charger, and Viction 1200va inverter.
Looking for a bit more education before I commit.
Thanks,
Ken Doyle
'75 Glenbrook
SE Kansas
On Fri, Jul 2, 2021, 12:40 PM John R. Lebetski
wrote:
> Right I did not restate a stock 80A alternator in my answer.because a
> larger alternator was not included in the original post. Stock system is
> balanced system. Go to a 100A alt and balance is upset. Especially the
> isolator. You blow open the engine side diode and voltage will go sky high
> to
> house side.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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