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:
|
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
|
|
|
|
Current Time: Fri Apr 26 05:00:03 CDT 2024
Total time taken to generate the page: 0.02679 seconds
|
GMCforum
Search
Help
Register
Login
Home
