Battery isolator problem

bfuller181 · 06-16-2019, 10:13 AM

My engine battery and my house battery appear to be killing each other. The bus sits in the driveway for a week and both batteries are dead. Jump, charge, wait a week, repeat. Wiring seems to be ok, but when I checked the solenoid this morning, I discovered a low voltage leak to the output terminal even when the solenoid trigger is off.

Can solenoids go bad? If not, what else could it be?

john61ct · 06-16-2019, 10:28 AM

Every device built by man will fail.

Get a decent DMM and teach yourself to use it. Be able to locate shorts, parasitic draws, high resistance points in connections, etc

bfuller181 · 06-16-2019, 10:31 AM

Would any of the suggestions you made explain how voltage is getting across an unpowered solenoid?

BlackJohn · 06-16-2019, 11:34 AM

Does the isolator make any sound when triggered with igniton ON? I think you could even feel a movement in it if you have someone work the key and you checking.
Only way is to test with a multimeter set on ohms first with no power on, then retest for voltage with power ON.

When your bus sits you might be wise to add a battery disconnect to the ground on the house batteries to prevent drain.
Solenoids do fail with age and heat buildup so ringing it out will disclose this.
Possible you have other parasitic draws going on but testing the isolator operation would be your first step.
Does your bus have a push button for "boost" starting if the start batteries are weak?

John

bfuller181 · 06-16-2019, 11:39 AM

Yes, the solenoid still makes an audible click when triggered by the powered fuse wire.

With no power, the solenoid reads roughly 1.5 Ohms across the main terminals.

One thought I had was that the solenoid is rated to 65A, but apparently the alternator has a max amperage of 105A - did I simply buy the wrong one and need to replace it with a higher rated version?

Is this an acceptable battery disconnect?
https://www.amazon.com/Disconnect-Ve...e%2C129&sr=1-8

thanks

peteg59 · 06-16-2019, 11:43 AM

That disconnect would work, but it doesn't seem to have a "removable" key, if that matters to you?

BlackJohn · 06-16-2019, 11:56 AM

Quote:

Originally Posted by bfuller181

Yes, the solenoid still makes an audible click when triggered by the powered fuse wire.

With no power, the solenoid reads roughly 1.5 Ohms across the main terminals.

One thought I had was that the solenoid is rated to 65A, but apparently the alternator has a max amperage of 105A - did I simply buy the wrong one and need to replace it with a higher rated version?

Is this an acceptable battery disconnect?
https://www.amazon.com/Disconnect-Ve...e%2C129&sr=1-8

thanks

Yes, that is one of many acceptable battery disconnects, pretty common item everywhere automotive. Made for marine generally adds to the price.

Ok, so sounds like the coil for the solenoid has continuity thru it, a good thing.
Now, do you have continuity from the +ve of the solenoid coil to either the start battery and or house battery? (with power On and OFF)
Should be no continuity with power OFF. If there is you have a bad internal plunger likely and need replace the isolator.

Yes, you could be having problems with the difference in amperage ratings although I am not positive of that at this point.

If you do happen to need an isolator, I would look at the ones with only three terminals. The make escapes me but the connections are alternator, starter and house batteries. I think it is Cole Hershee also but not positive.

John

bfuller181 · 06-16-2019, 12:06 PM

Quote:

Originally Posted by BlackJohn

Yes, that is one of many acceptable battery disconnects, pretty common item everywhere automotive. Made for marine generally adds to the price.

Ok, so sounds like the coil for the solenoid has continuity thru it, a good thing.
Now, do you have continuity from the +ve of the solenoid coil to either the start battery and or house battery? (with power On and OFF)
Should be no continuity with power OFF. If there is you have a bad internal plunger likely and need replace the isolator.

Yes, you could be having problems with the difference in amperage ratings although I am not positive of that at this point.

If you do happen to need an isolator, I would look at the ones with only three terminals. The make escapes me but the connections are alternator, starter and house batteries. I think it is Cole Hershee also but not positive.

John

With the solenoid off, there is a voltage of about 1 V across the main terminals - this is the voltage "leak" I mentioned in my first post (sorry if that wasn't clear). That was my reason for concern that I need to replace the solenoid.

As for the 3 post varieties, doesn't the housing of those need to be grounded anyway? What's the benefit to dropping the ground as its own post?

BlackJohn · 06-16-2019, 12:20 PM

Quote:

Originally Posted by bfuller181

With the solenoid off, there is a voltage of about 1 V across the main terminals - this is the voltage "leak" I mentioned in my first post (sorry if that wasn't clear). That was my reason for concern that I need to replace the solenoid.

As for the 3 post varieties, doesn't the housing of those need to be grounded anyway? What's the benefit to dropping the ground as its own post?

That voltage leak likely indicates that there is a backfeed through one or the other of the battery systems. You could disconnect one at a time to prove that.

Yes the housing will need be grounded wherever it is mounted but that is done through the bolts or screws you use. Just make sure the metal is clean and paint free in any case. You can also connect the old ground to the isolator housing when mounting it, then you have 2 grounds in effect.
The thing is with the 3 wire isolator, you feed it directly from the alternator output. Then 2 wires out, one to each battery bank positive. So the isolator isn't triggered till the engine runs, not just when key is ON.

Do the test above and then you can decide if you have to change the isolator. You should have no continuity between the main coil positive terminal and the house or start batteries which appears to be the opposite of what you are saying.

John

bfuller181 · 06-16-2019, 12:26 PM

You lost me. What are the other battery systems you're referring to?

BlackJohn · 06-16-2019, 12:30 PM

Quote:

Originally Posted by bfuller181

You lost me. What are the other battery systems you're referring to?

Sorry for the confusion

Simply you have the start battery system off the isolator and
you have the house battery system, off the isolator.
Just 2 systems, nothing else.

Got my merds wixed!

John

HazMatt · 06-16-2019, 12:32 PM

Start and House battery banks.
Is there any reason the switch couldn't be manually operated? Sure, ya may forget to charge the House side, but there's nothing to electronically glitch & spaz out, either...

bfuller181 · 06-16-2019, 12:33 PM

Right, so if I understand you, with the house battery disconnected from the solenoid but the start battery still connected, there shouldn't be any voltage across the terminals. That's what I have setup in the picture and what is creating the ~1V leak.

BlackJohn · 06-16-2019, 12:35 PM

Quote:

Originally Posted by HazMatt

Start and House battery banks.
Is there any reason the switch couldn't be manually operated? Sure, ya may forget to charge the House side, but there's nothing to electronically glitch & spaz out, either...

One problem at a time ..we haven't got this one licked yet.

John

david.dgeorge07 · 06-16-2019, 01:29 PM

If your isolator is bad I have a good working used bi-directional voltage sensing automatic isolator rated at 140 amps. I would sell it cheap.

It worked well I just decided to go to a manual switch so I could isolate the house batts from the bus when driving if I want.

Nice unit if it is what you need.

HazMatt · 06-16-2019, 01:48 PM

Quote:

Originally Posted by BlackJohn

One problem at a time ..we haven't got this one licked yet.

John

Well, no... But it was kinda on topic!

Quote:

Originally Posted by david.dgeorge07

If your isolator is bad I have a good working used bi-directional voltage sensing automatic isolator rated at 140 amps. I would sell it cheap.

It worked well I just decided to go to a manual switch so I could isolate the house batts from the bus when driving if I want.

Nice unit if it is what you need.

That answers my question, thanx!

Quote:

Originally Posted by bfuller181

Right, so if I understand you, with the house battery disconnected from the solenoid but the start battery still connected, there shouldn't be any voltage across the terminals. That's what I have setup in the picture and what is creating the ~1V leak.

It sounds like there is an internal fault; there should be zero voltage when disengaged, and it didn't appear any of your connections were touching anything they oughtn't...
That over amperage you mentioned may've damaged it after all.

john61ct · 06-16-2019, 01:51 PM

https://expeditionportal.com/forum/t...p-for-50.77503

HazMatt · 06-16-2019, 01:56 PM

Quote:

Originally Posted by john61ct

https://expeditionportal.com/forum/t...p-for-50.77503

That was a fun, informative read!
Think I'll have a beer...

BlackJohn · 06-16-2019, 03:14 PM

Quote:

Originally Posted by bfuller181

Right, so if I understand you, with the house battery disconnected from the solenoid but the start battery still connected, there shouldn't be any voltage across the terminals. That's what I have setup in the picture and what is creating the ~1V leak.

Yes you are following my thinking. I wasn't sure what the picture meant totally but that condition does not seem correct, the 1volt part should read "0"

And no leakage if the house battery is connected with the start battery disconnected?

Sounds like it may have fried internally. Would be interesting to open it if you go new, more amperage capability and much better heat sync case.

John

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