Battery Isolator issue

[kdgreene]

I am having a perplexing issue with the battery isolator installed in my camper. The old one appeared to have a bad solenoid so I replaced it with one made by Blue Sea. The issue is that the house batteries are not being charged.

When the engine is on, my multimeter shows that there is voltage of 14.6 coming into the isolator, as well as 14.6 going out the battery connection side of the isolator. However, as soon as I connect the battery charging wire from the house battery to the isolator, the voltage on BOTH sides of the isolator drop to that of the house batteries, which at this point is 12.8. So presently the house batteries are not being charged by the alternator. Does anyone have any suggestions as to what may be causing this? Thanks.

 

[Stan@FourWheel]

Have any pics on how you have it hooked up ?

 

[kdgreene]

Thanks. I am using the 7610 ACR, which looks the same as the photo you posted. I can grab a photo, but the wiring I have is the same.

The 7610 takes approx 2 minutes from the time the alternator begins to send current before it combines to the house battery. So will waiting for the combining to take effect, I kept my voltmeter probes on the unit watching the voltage. The incoming voltage was properly showing 14.6 from the alternator and 12.8 from the house batteries. As soon as the 7610 showed that it was combining the batteries, the voltage on the incoming side of the unit dropped to the same voltage as the house batteries. Moving the voltmeter to the starting battery showed that the alternator was continuing to work properly.

I am using solar primarily to charge my house batteries. What happened here is this: while on a trip earlier this fall, we experienced several days of bad weather which caused our solar charge to drop, which led us to realize that our existing Isolator was not working properly. When we returned home, I upgraded our isolator to the Blue Sea as our old isolator had been running very hot before it stopped working.

After installing the 7610 and turning off the solar, I was able to check the charging current from the alternator with the charge of the house batteries. The house batteries are only 2 years old and are still working very well.

 

[rando]

That sounds like your isolator is working correctly, but your alternator output is high, and the wiring between the alternator and camper are not up to the task of carrying the current. I am assuming your battery is pretty discharged for this test. When you connect the battery to the isolator, a lot of current flows to the battery and you are dropping a couple of volts between the alternator and the isolator. I am guessing soon after you connect the battery, the isolator shuts off and then the voltage in the input jumps back up to 14.x V when the current stops flowing?

You either need to improve the wiring between the camper and alternator, get a DC-DC charger or dial down your alternator voltage.

 

[kdgreene]

Thanks for the reply. The alternator with my Chevy 3500 is a high output alternator so the output can be up to 14.7. Nothing has changed or been modified on my set up in over two years, so I'm sure that there is a problem with the wiring.

Also, the battery is not very discharged during the testing as it usually is near or at full as a result of the solar charging system. But even at a voltage on the house batteries of 12.8. which is close to 100%, the battery monitor and the voltmeter should be registering a higher voltage as a result of the voltage coming from the alternator.

So, I'm back to square one in trying to track the issue down. I really appreciate the suggestions and assistance, I just can't figure out why the house batteries should become the dominate one after the isolator combines the two sets of batteries.

 

[pvstoy]

Check the wiring from the truck battery and seperator. Look at positive and negative wires for shorts or corried connections.

If you have circuit breakers at either end check to see if they have failed..

If you show 12.8 at truck side of seperator and 14.x at battery then there is problem with wiring from load collapse between.

 

[pvstoy]

even make sure the ground wire off of the seperator is clean and tight, and to a proper ground placement.

 

[kdgreene]

Thanks for the suggestions. I'll have to do some furthers tests to see what works.

 

[Vic Harder]

+1 to what rando said. Voltage drop from alternator to battery separator is a longstanding known issue with the default 12g wiring. IF, as rando suggests, the separator "separates", do you see the voltage spike back up on the input side? Let us know.

 

[kdgreene]

Yes, exactly. When it separates the voltage on the input spikes back to 14+, then when it combines the voltage drops again!

 

[Vic Harder]

Yes, exactly. When it separates the voltage on the input spikes back to 14+, then when it combines the voltage drops again!

Sounds like you will need to upgrade the wiring from camper to truck battery. rando's suggestion of a DC-DC charger is good as well, but I suspect you will need heavier gauge wire either way.