A neighbor's grandson and his wife are visiting , from Washington state, with the Mercedes van they're fitting out for full-timing. They're got it barely liveable with only 12 VDC wiring completed. On the way here, they had smoke, sparks, flames, and the fire department near Phoenix. The "isolator" was sparking and the lead from the two 220A AGM batteries 20 feet away melted almost in two inside a wall. I won't go into the faulty design decisions that allowed that to happen, like the absence of CB's, but want to ask for ideas:

This is the "isolator" (really a combiner) which first alerted him to a problem by emitting sparks:

amzn.to/2KUzWHM
or
https://www.amazon.com/dp/B00WTAFR5W?tag=amz-mkt-chr-us-20&ascsubtag=1ba00-01000-org00-win10-other-nomod-us000-pcomp-feature-scomp-wm-5&ref=aa _scomp

Since he threw the destroyed "isolator" away, I can't examine it for clues as to the cause of the problem. Does anyone have any experience with this device? I can only assume that it somehow shorted to ground internally, but I'm skeptical about that...

I'll try to help him correct his design decisions and will even offer him a Yandina 160A relay to connect as a "manual combiner/boost switch", but the linked "isolator" seems like a good buy -- unless its prone to such failures.

Any input appreciated; the young couple's going to be around for a while to use my shop and service rack to do more work on their rig.

Ken H.

The expected visit to my shop for today just got delayed until next week, so I won't have any more input until then.

However, I have learned one sorta strange fact during this, from researching the "Isolator". From all indications, our little community is the only one maintaining the "Isolator" vs "Combiner" syntax. In fact, the terms "Isolator", "Separator", and "Combiner" are used essentially interchangeably on the web.

Ken H.

Rich,

Thanks for the advice. Having no experience with AGM's, I need all the information I can get if I'm to be of any help to this young couple. One thing they told me, that really bothers me, is that they "...have 2 AGM's in the rear...". I presume they're in parallel and probably with no protection. Are the hazards of paralleled AGM's the same as with regular lead-acid?

When I briefly looked at the rear-mounted 12VDC house wiring, the connection of the main cable, which "melted down" at a 12" diameter coil behind a wall panel (ripped out by the fire department), had been severely overheated. In order to heat that 5/16" stud to blue/black, it had to be very severely overloaded, and probably not properly tightened. It's still unknown to me how the overload occurred

Ken H.