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| Unusual electrical issue [message #339144] |
Thu, 29 November 2018 00:06  |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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I just ran into an interesting issue on our Thanksgiving trip. After replacing a NEW alternator under warranty after little over 1000 miles, I was afraid the replacement was going bad 5000 miles later. The voltage would drop to 11.9 volts and randomly jump to 14+ at times. While observing -12 volts a semi truck passed and the voltage popped up to 14+ and seemed to drop as soon as the big rig passed. I noticed the same effect when going under an overpass. It then hit me-the solar panels (280 watts worth) are wired to the house battery bank and the alternator sense wire is attached to the same point on the isolator. It seems the voltage from the panels is making the alternator reduce output thinking the battery voltage is satisfied. Guess I'll have to install a relay to open the PV circuit when the ignition is energized. Who'd of thunk that would happen? It's always something to keep the gray matter going on these GMC's.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Unusual electrical issue [message #339145 is a reply to message #339144] |
Thu, 29 November 2018 00:18  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Nothing like the sudden realization that we have just outsmarted ourselves.
Keeps me humbler than I would otherwise be. Guess I ain't alone. (Grin)
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Wed, Nov 28, 2018, 10:09 PM Hal StClair
wrote:
> I just ran into an interesting issue on our Thanksgiving trip. After
> replacing a NEW alternator under warranty after little over 1000 miles, I
> was
> afraid the replacement was going bad 5000 miles later. The voltage would
> drop to 11.9 volts and randomly jump to 14+ at times. While observing -12
> volts a semi truck passed and the voltage popped up to 14+ and seemed to
> drop as soon as the big rig passed. I noticed the same effect when going
> under an overpass. It then hit me-the solar panels (280 watts worth) are
> wired to the house battery bank and the alternator sense wire is attached to
> the same point on the isolator. It seems the voltage from the panels is
> making the alternator reduce output thinking the battery voltage is
> satisfied.
> Guess I'll have to install a relay to open the PV circuit when the
> ignition is energized. Who'd of thunk that would happen? It's always
> something to
> keep the gray matter going on these GMC's.
> Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] Unusual electrical issue [message #339146 is a reply to message #339145] |
Thu, 29 November 2018 00:50 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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Try moving the sense line to the engine battery side of the isolator.
On Wed, Nov 28, 2018 at 10:16 PM James Hupy wrote:
> Nothing like the sudden realization that we have just outsmarted ourselves.
> Keeps me humbler than I would otherwise be. Guess I ain't alone. (Grin)
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>
> On Wed, Nov 28, 2018, 10:09 PM Hal StClair
> wrote:
>
>> I just ran into an interesting issue on our Thanksgiving trip. After
>> replacing a NEW alternator under warranty after little over 1000 miles, I
>> was
>> afraid the replacement was going bad 5000 miles later. The voltage would
>> drop to 11.9 volts and randomly jump to 14+ at times. While observing -12
>> volts a semi truck passed and the voltage popped up to 14+ and seemed to
>> drop as soon as the big rig passed. I noticed the same effect when going
>> under an overpass. It then hit me-the solar panels (280 watts worth) are
>> wired to the house battery bank and the alternator sense wire is
> attached to
>> the same point on the isolator. It seems the voltage from the panels is
>> making the alternator reduce output thinking the battery voltage is
>> satisfied.
>> Guess I'll have to install a relay to open the PV circuit when the
>> ignition is energized. Who'd of thunk that would happen? It's always
>> something to
>> keep the gray matter going on these GMC's.
>> Hal
>> --
>> 1977 Royale 101348,
>>
>> 1977 Royale 101586, Diesel powered,
>>
>> 1975 Eleganza II, 101230,
>>
>> 1974 Eagle Bus 45',w/slideout,
>>
>> Rio Rancho, NM
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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| Re: Unusual electrical issue [message #339156 is a reply to message #339148] |
Thu, 29 November 2018 10:28 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Moving the sense wire would eliminate the problem but I'm not willing to sacrifice the battery capacity loss the .6 volt loss the isolator creates. We do quite a bit of off grid camping and need all the battery we can get. I think a simple relay will make it all better  . But thanks for the suggestions.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
[Updated on: Thu, 29 November 2018 10:28] Report message to a moderator |
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| Re: [GMCnet] Unusual electrical issue [message #339157 is a reply to message #339156] |
Thu, 29 November 2018 10:58 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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Senior Member |
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The 0.6volt drop should be the same for both sides of the isolator and if
you think your house batteries are lower than the engine battery you could
turn the relay on between the batteries.
On Thu, Nov 29, 2018 at 8:28 AM Hal StClair
wrote:
> Moving the sense wire would eliminate the problem but I'm not willing to
> sacrifice the battery capacity loss the .6 volt loss the isolator creates.
> We
> do quite a bit of off grid camping an need all the battery we can get. I
> think a simple relay will make it all better :p . But thanks for the
> suggestions.
> Hal
> --
> 1977 Royale 101348,
>
> 1977 Royale 101586, Diesel powered,
>
> 1975 Eleganza II, 101230,
>
> 1974 Eagle Bus 45',w/slideout,
>
> Rio Rancho, NM
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
*John Phillips*
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Unsubscribe or Change List Options:
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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| Re: [GMCnet] Unusual electrical issue [message #339164 is a reply to message #339158] |
Thu, 29 November 2018 18:41 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Combining the batteries with the combiner switch didn't make the alternator charge as it still saw the PV voltage. I doubt using a combiner would work as it accomplishes the same task as the manual switch. The relay would be a much less expensive alternative I'd guess.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Unusual electrical issue [message #339169 is a reply to message #339144] |
Fri, 30 November 2018 06:15 |
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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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Hal,
Using the combiner will allow charging of both House and Chassis batteries from either alternator or solar cells automatically.
The alternator voltage sense is a feed-back to the alternator of the battery voltage. The 0.7V drop across the isolator is a non-issue because the voltage sense line tells the alternator to increase its voltage to offset this loss. There is also a voltage drop in the main wire from the alternator to the isolator which at high currents may be more than the isolator drop. Again the voltage sense line will compensate for this.
If the solar is outputting more voltage than the alternator's regulator is internally set for, then through its voltage sense line it will back off its charging rate. Between the two sources I would suspect they would come to a load sharing state depending on how much the solar is producing. Depending on your solar controller, it should start with a high rate of charge, then back off to a float voltage.
The alternator's regulator is not smart at all. It is set for a float rate voltage but being current limited by the engine speed and the alternator's internal resistance. This should not be an issue though since your solar controller will back off to a float voltage and with the load of the engine accessories, I doubt if it will get to its full voltage without the help of the engine alternator.
Just my shade-tree ex farm-boy mechanic with 40 years experience in public safety communications & electronics keeping systems alive at all costs during power outages through backup and redundant automatic fallback systems... way of seeing things.
But I could be all wrong.
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: Unusual electrical issue [message #339178 is a reply to message #339144] |
Fri, 30 November 2018 08:09 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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The alternator is " slightly smart" in that all GM alternators are temperature compensating. Fine Voltage trim is inverse to internal regulator temp, which is an emulation of expected battery temp as weather effects both.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Unusual electrical issue [message #339206 is a reply to message #339169] |
Fri, 30 November 2018 22:08 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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The solar voltage must be higher than the alternators regulator's set point because it won't charge when sunlight hits the panels directly. The two sources may come to balance eventually but the engine batteries not being charged until that happens certainly doesn't create a warm fuzzy feeling. I was reading less than 12 volts during this condition on the engine side. I guess I'm confused with your reference of the voltage drop being a non issue-if the sense wire is on the engine bank, the house is going to be charged at the reduced rate. The house bank can't get to max voltage in any reasonable length of time at the reduced charge rate. The sense line is only reading the bank it's connected to for compensation, not the second bank. What am I missing here?
Hal
RF_Burns wrote on Fri, 30 November 2018 05:15Hal,
Using the combiner will allow charging of both House and Chassis batteries from either alternator or solar cells automatically.
The alternator voltage sense is a feed-back to the alternator of the battery voltage. The 0.7V drop across the isolator is a non-issue because the voltage sense line tells the alternator to increase its voltage to offset this loss. There is also a voltage drop in the main wire from the alternator to the isolator which at high currents may be more than the isolator drop. Again the voltage sense line will compensate for this.
If the solar is outputting more voltage than the alternator's regulator is internally set for, then through its voltage sense line it will back off its charging rate. Between the two sources I would suspect they would come to a load sharing state depending on how much the solar is producing. Depending on your solar controller, it should start with a high rate of charge, then back off to a float voltage.
The alternator's regulator is not smart at all. It is set for a float rate voltage but being current limited by the engine speed and the alternator's internal resistance. This should not be an issue though since your solar controller will back off to a float voltage and with the load of the engine accessories, I doubt if it will get to its full voltage without the help of the engine alternator.
Just my shade-tree ex farm-boy mechanic with 40 years experience in public safety communications & electronics keeping systems alive at all costs during power outages through backup and redundant automatic fallback systems... way of seeing things.
But I could be all wrong.
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Unusual electrical issue [message #339210 is a reply to message #339144] |
Sat, 01 December 2018 01:09 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Senior Member |
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Hal wrote:
"I guess I'm confused with your reference of the voltage drop being a non issue-if the sense wire is on the engine bank, the house is going to be charged at the reduced rate. The house bank can't get to max voltage in any reasonable length of time at the reduced charge rate. The sense line is only reading the bank it's connected to for compensation, not the second bank. What am I missing here?"
Hal, the situation you describe could only occur if the ENGINE battery were being charged from another source, the way your house battery is now. Otherwise, the alternator will work to provide ~14.5V PLUS the 0.6V drop to the center terminal of the isolator. Unless there's a problem (open diode) in the isolator, this should send ~14.5V to BOTH output terminals, and therefore all the charge the system is capable of supplying.
I'm thinking this may all be moot for your house battery, as your solar panels must have it MORE than fully charged (ie: OVER 14.5V) to cause your alternator regulator (when sensing the same point your panels are feeding) to cut alternator output to essentially nothing. Do you have a functioning voltage regulator on your solar system? Are you sure the isolator is good?
Remember, the alternator's regulator controls ONLY voltage, unlike with the old generator vehicles. Alternators are self-limitting for current.
HTH,
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: [GMCnet] Unusual electrical issue [message #339211 is a reply to message #339210] |
Sat, 01 December 2018 04:30 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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Senior Member |
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The alternator will charge the lower voltage battery no matter which side
the sense line is tied to.
You need a charge controller for the solar to be safe.
On Fri, Nov 30, 2018 at 11:13 PM Richard H Staples
wrote:
> Hal wrote:
> "I guess I'm confused with your reference of the voltage drop being a non
> issue-if the sense wire is on the engine bank, the house is going to be
> charged at the reduced rate. The house bank can't get to max voltage in
> any reasonable length of time at the reduced charge rate. The sense line is
> only reading the bank it's connected to for compensation, not the second
> bank. What am I missing here?"
>
> Hal, the situation you describe could only occur if the ENGINE battery
> were being charged from another source, the way your house battery is now.
> Otherwise, the alternator will work to provide ~14.5V PLUS the 0.6V drop
> to the center terminal of the isolator. Unless there's a problem (open
> diode) in the isolator, this should send ~14.5V to BOTH output terminals,
> and therefore all the charge the system is capable of supplying.
> I'm thinking this may all be moot for your house battery, as your solar
> panels must have it MORE than fully charged (ie: OVER 14.5V) to cause your
> alternator regulator (when sensing the same point your panels are feeding)
> to cut alternator output to essentially nothing. Do you have a functioning
> voltage regulator on your solar system? Are you sure the isolator is good?
> Remember, the alternator's regulator controls ONLY voltage, unlike with
> the old generator vehicles. Alternators are self-limitting for current.
>
> HTH,
> Rick Staples
> --
> Rick Staples, '75 Eleganza, Johnstown, CO
>
> "Advice is a dangerous gift, even from the Wise to the Wise, and all paths
> may run ill." -Tolkien
>
> _______________________________________________
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*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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| Re: [GMCnet] Unusual electrical issue [message #339221 is a reply to message #339211] |
Sat, 01 December 2018 11:24 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Put the sense line back where it belongs on the engine side and be done with it. The sense line is simply to tell the alternator to raise or lower the voltage to make up for any loss in the circuit (including the isolator loss). There is not need for added combiners, relays, etc.
You are worrying about and trying to engineer around something that is not a problem to start with.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Unusual electrical issue [message #339227 is a reply to message #339221] |
Sat, 01 December 2018 16:37 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Ken Burton wrote on Sat, 01 December 2018 12:24Put the sense line back where it belongs on the engine side and be done with it. The sense line is simply to tell the alternator to raise or lower the voltage to make up for any loss in the circuit (including the isolator loss). There is not need for added combiners, relays, etc.
You are worrying about and trying to engineer around something that is not a problem to start with.
Hal,
I am completely inline with KenB on this, and if you want to stop worrying about it, after you put the alternators sense lead back where it should be, then move the pick-up point for you system voltmeter to where it should really be and that would be the main engine system supply line anywhere. First thought would be the downstream side of the fusible link. Now it will be reading the system and that is really all you should be concerned with.
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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| Re: [GMCnet] Unusual electrical issue [message #339231 is a reply to message #339227] |
Sat, 01 December 2018 18:28 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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Senior Member |
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As long as current is generated it will go to the lower voltage battery. If
the chassis battery voltage is less than the regulator setpoint current
will be generated.
On Sat, Dec 1, 2018 at 2:38 PM Matt Colie wrote:
> Ken Burton wrote on Sat, 01 December 2018 12:24
>> Put the sense line back where it belongs on the engine side and be done
> with it. The sense line is simply to tell the alternator to raise or
>> lower the voltage to make up for any loss in the circuit (including the
> isolator loss). There is not need for added combiners, relays, etc.
>>
>> You are worrying about and trying to engineer around something that is
> not a problem to start with.
>
> Hal,
>
> I am completely inline with KenB on this, and if you want to stop worrying
> about it, after you put the alternators sense lead back where it should be,
> then move the pick-up point for you system voltmeter to where it should
> really be and that would be the main engine system supply line anywhere.
> First thought would be the downstream side of the fusible link. Now it
> will be reading the system and that is really all you should be concerned
> with.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
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*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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