Battery Isolator Problem

[peteua636]

Hello....<br /><br />I have a 2 altenator / 3 battery system. When I am at 3000 or more rpm the voltage gauges on both engines drop. When I return back to idle they go back up to around 14 volts. I have checked the belts. Was wondering how to tell if the isolator is going out?<br /><br />Thanks<br />Pete

 

[Boatist]

Re: Battery Isolator Problem

If you have a volt meter check the voltage from the alternator on the input to your isolator. Voltage should be 13.8 to 15 volts out of your alternator. Then check the isolator ouput voltage or the battery terminal voltage. It should also be 13.1 to 14.3 volts. You need to check it when the voltage is low. <br />It could be a bad voltmeter, loose battery cable, alternator, or isolator.<br /><br />Good Luck

 

[amirm]

Re: Battery Isolator Problem

I don't have one but I assume the isolator is just a high-power diode and as such, it would have a 0.6 volt drop across from it. That is what Boatist is saying above. If the voltage drops a lot more than this, then that could be the problem. But somehow I doubt it. A diode would normally short out or become 100% open. They can have the symptoms you have but that would more uncommon.<br /><br />I would look at loose connectors as Boatist says. At higher RPMs, you have more current coming in, making secure connections more of a necessity. The second bet would be the alternator.<br /><br />Amir

 

[Richard Petersen]

Re: Battery Isolator Problem

The belts are slipping more at the higher speeds because the alternators are using more horsepower. Adjust or replace the slipping belts.

 

[18rabbit]

Re: Battery Isolator Problem

Originally posted by amir:<br /> I don't have one but I assume the isolator is just a high-power diode ...

Amir – that is exactly what a battery isolator is...and why I don’t like them.