Hi All
Curiosity got the better of me - so I just went ahead and disconnected the unit to test it.
Glad I did, as first thing I noticed after removing both fuses and testing they were OK, was the unit was so hot I couldn’t touch the back of it when I went to disconnect the VE Direct cable. Which I immediately knew wasn’t right - as the unit has been “off” in VictronConnect for a few hours. Likewise the input (alternator) hadn’t been above the start charging voltage for a similar period of time.
I briefly put the fuses back in, and my clamp meter showed It seemed to be drawing ~5A into the unit from the output side which was obviously all being dissipated as heat. I’d say it has a failed mosfet, diode or something internal. The internal current measurement of the unit was 0A and my SmartShunt was reading -4.7A discharging - verifying the clamp meter measurement. All other loads were disconnected.
Tested the ground cable/impedence while I was there - that was all good.
I’d say those here who had a fuse blow were lucky - the fuse did what it should, protecting the cables and internals of the unit.
My input and output fuses were 70A MIDI - maybe too high in retrospect - but honestly was selected to protect the 25mm2 cables ~1.5m long.
I’ve just left it isolated now and I’ll organise to return it via my supplier for assessment by Victron. Shame - it had been running daily since April without issue.
Kind regards
Elliot A