Stupid me.

[Havok]

Tried to start the engine while batteries were charging. Heard a small pop and power went out. Now when I turn on the battery isolator, power is available, but then if anything is turned on i.e. ignition or lights, power drops out. Checked all fuses they seem okay, could this be the battery isolator, or any ideas?

[mm58]

Did the batteries ever get fully charged up?

[VinceAtReal4x4s]

How do you know power is available? Test each battery?
You should be able to start it while charging with no problem.

[Havok]

Thanks for responding. Both batteries fully charged, charger was on boost when I attempted to start.

[VinceAtReal4x4s]

Boost is just a higher amperage setting to help spin your starter.

What did you mean by "power is available"? What's telling you that?

[Havok]

Full power is registered on the voltage regulator when the isolation switch is turned on, but then shuts down when anything is activated.

[rmel]

Not sure exactly what your describing, but I'll take a stab at it.

With the Ground switch closed, and no load presented e.g. nothing
ON, your seeing a full 24V+ -- right? Then you turn stuff ON then
the voltage drops.

If that's what your seeing, check for corroded or loos connections,
a bad ground switch or batteries.

First measure the voltage at your batteries, when your voltage drops.
If your batteries do not drop in voltage then that's a bad connection
somewhere. Also measure the voltage at the Battery Ground terminal
that connects to the Ground Switch, with one lead to the chassis. If you
see significant voltage there your switch is bad.

And if you see your Battery voltage drop measured at the battery terminals,
then it's time for new batteries.

[Havok]

Thanks, very helpful.