So we installed a Victron battery monitor
and in the saga of putting the shunt in backwards had some drama with having to reverse the PCB board and losing one of the screws! But that isn't what this is about. After getting that all sorted out we connected it up and the monitor
wouldn't turn on.
Well I suspected immediately that the pos+ lead wire was the problem. It should work if it has power right?
I went through measure voltage with my multimeter and between the end of the lead and the pos bus I found it was showing 4v. Odd. The batteries were at 12.9v.
I checked from the pos bus to the first part of the post lead where the fuse holder is and it read the correct 12.9v. Then I checked the other side. 4v.
So I took the fuse out and just pushed the two ends of the cheap
little fuse hold together and the thing came on. Turned out the fuse itself was the issue.
The fuse is a little 1amp glass fuse. It doesn't look burned and it does conduct some current
but it drops voltage from 12.9v to 4v.
Has anyone ever heard of this? I thought when a fuse blew it just wouldn't conduct at all. Do I have some sort of mutant defective fuse? Ah well, I'm putting a better fuse holder in and replacing it. Just thought I'd share a rather frustrating discovery.