Dual Battery Setup

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Noob, but trying to learn
May 30, 2011
Pflugerville Tx
New Cruiser has a dual battery setup.

1 battery is new, 1 is completely dead, like microvolts.

I don't see a battery isolator, but since the dead battery isn't killing the good one, I suspect one is there.

It there a test i can do to see if one is there, but tucked away somewhere?

Continuity from bat 1+ to bat 2 +, maybe?

I have an optima yellow top spare around, I'd like to use if it's got an isolator.


If you know one is charged and the other is only showing microvolts, then you already did the test. If there wasn't a disconnect, then they would show the same (or very, very close) voltage.
Thanks Code red, I suspected that, but I only know the theory.

I appreciate you confirming it.
Trace the "hot" wires... that should lead to the isolator or relay that is separating the batteries. I would trace the ones from the second battery that is mounted on the drivers side. Should be the big fat (like 4 guage) wire.
when batteries are wired in parallel in a circuit the voltages are equal but the currents add. So if you didn't have an isolator between the two batteries the strong battery would essentially try to charge the weak battery and the voltage measured would be some combined voltage significantly lower than the expected 12.x volts.
Turns out there was not an isolator, just a big old skool boat switch :)

Going to replace it with a 140 amp smart isolator, that will charge bat 1 first, then bat 2.

Don't want them in parallel normally because on is Lead Acid and the other is an AGM yellow top I had laying around, I slapped in to replace the Microvolt one.
(which after 2 days on the charger and conditioner reached a peak of 10 volts! :D )

Will be able to run a switch to put them in parallel at need like starting.


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