Home » Public Forums » GMCnet » Testing the battery isolator
Testing the battery isolator [message #189146] |
Sun, 04 November 2012 08:04 |
kerry pinkerton
Messages: 2565 Registered: July 2012 Location: Harvest, Al
Karma: 15
|
Senior Member |
|
|
I split this from my "BATTERY OR STARTING ISSUES" thread because the isolator is a different component. The original thread is at:
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&th=24037&start=0&rid=2555
[quote title=Mike Miller wrote on Sat, 03 November 2012 11:22]Quote: | ... An isolator is just a pair of diodes. To explain the system: Think of "check valves" in an air system. Electrical juice can only flow one way and like a check valve restricts some air flow, the isolator does drop a little voltage as it works. SO... The center post is normally the input and the outer posts are normally the outputs. So, under normal operation, the center post should have higher voltage than the outer ones.
This would be cause battery charging problems if you had an alternator that regulates based on the voltage at the alternator output. (AKA: single wire alternator systems.)
Our alternator system is designed to sense the voltage on the engine battery side of the isolator, it will increase the voltage applied to the center post to make the output posts high enough to charge the batteries.
So... now that you "know" something about the system, how would YOU check the isolator?
|
Dang Mike, you're not supposed to put me on the spot and open me up to ridicule. I do that enough by myself.
Seriously, based on what I THINK I know (as opposed to what is the actual facts). This is how I would test the isolator.
1- Disconnect from shore power.
2- Set my meter to 25VDC (over 13 V) range
3- Put the negative lead (black) of my meter on a good ground.
4- Verify the ground by putting the positive lead of the meter (red) to the Positive terminal of the engine battery. Should read 12+ volt depending on battery state.
5- Start the engine. The voltage on the battery should increase by about 3/4 Volt. Perform same test on house battery.
If voltage does not increase at the battery (s) and the alternator is working, either the isolator OR the wiring is suspect. To test the isolator:
1- With engine running, check voltage at center lug of isolator. It should be 13.5 V or so (alternator output V)
2- Check voltage at the other two lugs. If voltage is not the same on the top and bottom lugs, then the corresponding diode has failed and the unit should be replaced (repaired??)
3- If voltage is present on the output lugs but not at the battery, the wiring or connection is bad.
To verify the shore power 120 to 12V power supply is working, shut off engine, plug into shore power (or start generator), and measure voltage at center terminal. Again, should be about 3/4V+ more than battery voltage.
OK, that is what I think I know. Until confirmed, please don't run out and rip apart your coach based on this process.
Now a question. How does battery condition effect measured voltage? Again, what I think I know is that the original BUZZ box converter will always put out the same voltage to the battery regardless of battery state (fully charged or not). I have a new 'smart' converter that is supposed to charge at lesser and lesser rates as the battery comes up to full charge. I THINK that the alternator will also charge at different rates but am not sure.
Ok, pass, fail, what?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
|
|
|
Re: Testing the battery isolator [message #189161 is a reply to message #189146] |
Sun, 04 November 2012 11:17 |
|
Matt Colie
Messages: 8547 Registered: March 2007 Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
Kerry Pinkerton wrote on Sun, 04 November 2012 09:04 | I split this from my "BATTERY OR STARTING ISSUES" thread because the isolator is a different component. The original thread is at:
<snip>
Dang Mike,
<snip>
If voltage does not increase at the battery (s) and the alternator is working, either the isolator OR the wiring is suspect. To test the isolator:
1- With engine running, check voltage at center lug of isolator. It should be 13.5 V or so (alternator output V)
2- Check voltage at the other two lugs. If voltage is not the same on the top and bottom lugs, then the corresponding diode has failed and the unit should be replaced (repaired??)
3- If voltage is present on the output lugs but not at the battery, the wiring or connection is bad.
|
**=> Here is a problem <=** See below Quote: | To verify the shore power 120 to 12V power supply is working, shut off engine, plug into shore power (or start generator), and measure voltage at center terminal. Again, should be about 3/4V+ more than battery voltage.
OK, that is what I think I know. Until confirmed, please don't run out and rip apart your coach based on this process.
Now a question. How does battery condition effect measured voltage? Again, what I think I know is that the original BUZZ box converter will always put out the same voltage to the battery regardless of battery state (fully charged or not). I have a new 'smart' converter that is supposed to charge at lesser and lesser rates as the battery comes up to full charge. I THINK that the alternator will also charge at different rates but am not sure.
Ok, pass, fail, what?
|
Kerry,
The converter is not typically connected through the isolator.
When charge the house bank with the AC power, the measured voltage of the house bank will go to charge level (13+), the alternator stay at Zero and the engine bank will see quiescent (~12.6).
Answers to questions:
A discharged battery should not be below 11.0V, and a resting full charge will get you to 12.6V~13.0 (depending on battery electrolyte density - put 12.6 in your head).
Typical automotive alternators maintain a constant output voltage of around 14.5V.
That help?
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
|
|
|
Re: Testing the battery isolator [message #189207 is a reply to message #189161] |
Sun, 04 November 2012 19:22 |
Ken Burton
Messages: 10030 Registered: January 2004 Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
The simple way to test the isolator, if the alternator is working, is to connect the negative lead of your meter to the plate that the isolator is mounted on and probe the 3 terminals of the isolator.
The center terminal should be around 14.7 volts and the other two should be .7 volt lower or around 14.0.
Note: If you also have a combiner installed, disconnect the damn thing before taking any measurements.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
Re: Testing the battery isolator [message #189256 is a reply to message #189146] |
Mon, 05 November 2012 14:12 |
|
mike miller
Messages: 3576 Registered: February 2004 Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
Kerry Pinkerton wrote on Sun, 04 November 2012 06:04 | ... Seriously, based on what I THINK I know (as opposed to what is the actual facts). This is how I would test the isolator.
1- Disconnect from shore power.
2- Set my meter to 25VDC (over 13 V) range
3- Put the negative lead (black) of my meter on a good ground.
4- Verify the ground by putting the positive lead of the meter (red) to the Positive terminal of the engine battery. Should read 12+ volt depending on battery state.
5- Start the engine. The voltage on the battery should increase by about 3/4 Volt. Perform same test on house battery.
If voltage does not increase at the battery (s) and the alternator is working, either the isolator OR the wiring is suspect. To test the isolator:
1- With engine running, check voltage at center lug of isolator. It should be 13.5 V or so (alternator output V)
2- Check voltage at the other two lugs. If voltage is not the same on the top and bottom lugs, then the corresponding diode has failed and the unit should be replaced (repaired??)
3- If voltage is present on the output lugs but not at the battery, the wiring or connection is bad.
To verify the shore power 120 to 12V power supply is working, shut off engine, plug into shore power (or start generator), and measure voltage at center terminal. Again, should be about 3/4V+ more than battery voltage.
OK, that is what I think I know. Until confirmed, please don't run out and rip apart your coach based on this process.
Now a question. How does battery condition effect measured voltage? Again, what I think I know is that the original BUZZ box converter will always put out the same voltage to the battery regardless of battery state (fully charged or not). I have a new 'smart' converter that is supposed to charge at lesser and lesser rates as the battery comes up to full charge. I THINK that the alternator will also charge at different rates but am not sure.
Ok, pass, fail, what?
|
I finally had time to read again...
I would say "pass." But with the following comments:
-- The measured voltage on the center post should be a little higher than 13.5v as you should be around that (as charging voltage) on the outer posts.
-- I would also check the center post for zero volts with the engine not running to ensure that the isolator has not been by-passed (relatively common) or shorted (not so common).
-- From the factory the converter only charges the house battery. So you should NOT have anything on ethe input to the isolator if the engine is not running... pugged in or not. Some have added a "battery combiner" to connect the house and engine batteries when either battery has a charging voltage, but I suspect there are more coaches without than with combiners.
-- "How does battery condition effect measured voltage?" A bad battery can cause lower measurements, mostly noticed when no other voltage is being applied but can draw down even normally good charging voltages.
-- A good modern converter/charger is always a good idea over the old buzz box.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
|
|
|
|
Re: Testing the battery isolator [message #229942 is a reply to message #189207] |
Fri, 15 November 2013 16:54 |
sgltrac
Messages: 2797 Registered: April 2011
Karma: 1
|
Senior Member |
|
|
Ken and others, is there a simple way to test an un installed isolator to verify if it is good?
Thanks
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
|
|
|
|
|
Re: Testing the battery isolator [message #229948 is a reply to message #229942] |
Fri, 15 November 2013 17:04 |
tphipps
Messages: 3005 Registered: August 2004 Location: Spanish Fort, AL
Karma: 9
|
Senior Member |
|
|
Cheap or free Harbor Freight Multi-meter, set for diode, test from center terminal to outside posts. Meter buzzes, good diode section. No buzz, no good. Switch leads to double check. Bad diode section equals bad isolator.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
|
|
|
Re: [GMCnet] Testing the battery isolator [message #229953 is a reply to message #229948] |
Fri, 15 November 2013 17:29 |
sgltrac
Messages: 2797 Registered: April 2011
Karma: 1
|
Senior Member |
|
|
What is the symbol for diode?
Todd Sullivan
Sully
77 royale
Seattle
> On Nov 15, 2013, at 3:04 PM, Thomas Phipps <tph1pp5@yahoo.com> wrote:
>
>
>
> Cheap or free Harbor Freight Multi-meter, set for diode, test from center terminal to outside posts. Meter buzzes, good diode section. No buzz, no good. Switch leads to double check. Bad diode section equals bad isolator.
> Tom, MS II
> --
> 1975 GMC Avion, under forever re-construction
> Vicksburg, MS. 3.7 miles from I-20
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
|
|
|
|
|
|
Re: [GMCnet] Testing the battery isolator [message #229962 is a reply to message #229942] |
Fri, 15 November 2013 18:44 |
jhbridges
Messages: 8412 Registered: May 2011 Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Sure, with your ohmmeter. You should see a front to back ratio of a thousand or more. If you have a cheeeep digital meter, it may not be capable of biasing the diode in question enough to turn it on. Use a 12V bulb and put each half of the isolator in series wioth the bulb and battery. One direction it should light, the other stay dark. If it kights both ways, that diode is shorted. If it doesn't light at all, that diode is open.
Basically: chassis + I<-alt->I+house, the ->I being the diodes.
--johnny
From: sgltrac <sgltrac@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Friday, November 15, 2013 5:54 PM
Subject: Re: [GMCnet] Testing the battery isolator
Ken and others, is there a simple way to test an un installed isolator to verify if it is good?
Thanks
--
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
Re: Testing the battery isolator [message #229966 is a reply to message #189146] |
Fri, 15 November 2013 18:57 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Another quick test ....meter on DCV engine running meter center to house side and center to chassis side. You should see about .7 in both cases. No voltage means a shorted diode on that side and greater an open.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
Re: [GMCnet] Testing the battery isolator [message #229990 is a reply to message #229962] |
Fri, 15 November 2013 20:46 |
sgltrac
Messages: 2797 Registered: April 2011
Karma: 1
|
Senior Member |
|
|
I said simple Johnny ;)
Todd Sullivan
Sully
77 royale
Seattle
> On Nov 15, 2013, at 4:44 PM, Johnny Bridges <jhbridges@ymail.com> wrote:
>
> Sure, with your ohmmeter. You should see a front to back ratio of a thousand or more. If you have a cheeeep digital meter, it may not be capable of biasing the diode in question enough to turn it on. Use a 12V bulb and put each half of the isolator in series wioth the bulb and battery. One direction it should light, the other stay dark. If it kights both ways, that diode is shorted. If it doesn't light at all, that diode is open.
>
> Basically: chassis + I<-alt->I+house, the ->I being the diodes.
>
> --johnny
>
> From: sgltrac <sgltrac@gmail.com>
> To: gmclist@temp.gmcnet.org
> Sent: Friday, November 15, 2013 5:54 PM
> Subject: Re: [GMCnet] Testing the battery isolator
>
>
>
>
> Ken and others, is there a simple way to test an un installed isolator to verify if it is good?
>
> Thanks
> --
> Sully
> 77 Royale basket case.
> Future motorhome land speed record holder(bucket list)
> Seattle, Wa.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
|
|
|
Goto Forum:
Current Time: Fri Apr 26 09:22:01 CDT 2024
Total time taken to generate the page: 0.01485 seconds
|