How To Tell If A Battery Isolator Is Bad. Performing a load test. Look for a round sticker that has a month and year on your battery if you dont know when it was replaced last.
I installed the polaris dual battery isolator and when you trickle charge if you hook up to the main battery when it is fully charged it then closes the coil and connectes the two batteries to charge the aux. My old one had 3 wire terminals my new one has 4. Ruptured or cracked plastic casing.
Next take the red lead of the voltmeter and place it on the positive terminal.
You can only tell if a battery is bad or good if you inspect the battery regularly and test it if need be. An isolator works with a diode system that allows one-directional flow whereas the separator has a solenoid function that can choose to pull power from either source. I know in theory all power should run to the battery and not back towards the solar panels but electricity always follows the path of least resistance. Check the voltage at the second battery with the engine running.
