Problem with Redarc Battery Isolator / Secondary Battery

[gav]

I have a secondary battery that lost it's charge. While investigating I noticed that the Redarc battery isolator was behaving unexpectedly.

The isolator would briefly light up, then immediately turn off. The negative lead from the secondary battery, which leads directly from the negative terminal to the truck body, would jump each time. This process would repeat itself as you can see in the video. Any idea what the issue might be or how to diagnose it?

The primary battery has a charge just over 12.7 volts.

https://www.youtube.com/watch?v=UEgP1TPAf8A

[gav]

Just in case someone stumbles across this thread with a similar issue. I'm getting some good info from the following:

http://www.nissanpatrol.com.au/forums/s ... ry-Battery

[MihiT]

12.7 is low and may be drawing down too much current, causing voltage drop tripping out the cutoff.
Primary side should be 14.4 when running.

[gav]

@MihiT - thanks for the input. Turned out that the aux battery needed replacing as a cell had failed or something.