G'day all,
Thought I would post an update as we have found a solution to the problem. After the car had been towed to the auto electrician, that night I was sitting looking at some wiring diagrams which I had downloaded from the Victron website. I had used these as the basis of designing the setup in the rear of the Fiat.
There are several components not installed, like the lithium batteries, associated battery monitors, remote protect, inverter etc, but the solar, dc to dc (Orion) solar panels, -ve and =ve buses and the shunt are all fitted.
(edit) the site wouldn't let me post a link to the diagram so I made another post to hit '5' and the link is now two posts below. refer to that link and what I said in last sentence might make sense !
It dawned on me that although I had a cable running from starter -ve through the DC to DC charger to the battery negative (via the neg bus and shunt), and even though the neg bus was grounded to the chassis, there was no direct cable from the front battery -ve to the rear -ve bus - just the chassis earth. I noticed in the diagram that there was a dedicated cable going from front battery to -ve shunt in the rear.
So the next morning first thing I went out there and the same problem still existed, 7.5v between starter -ve terminal and the chassis.
I disconnected the -ve cables at the DC to DC charger and connected them together, thus bypassing it and making a clean path for the electrons to follow.
Low and behold the voltage disappeared between chassis and earth, the BMV began reading correct starter battery voltage and all the problems disappeared. Accessories on, car started fine.
So it was certainly an earthing issue, but nothing to do with the factory wiring. Luckily for us the mechanics had not started work and cost us nothing. tow was under roadside assistance.
I have since added a new cable linking front and rear -ve terminals for direct path for elecetrons to flow and have re-connected the DC to DC charger and all is good.
I still can't work out why though, when I physically disconnected everything from the rear to the front, that the gremlins remained. They too should have disappeared at that time !
Thanks for everyone's assistance on this. You all helped greatly.
Thought I would post an update as we have found a solution to the problem. After the car had been towed to the auto electrician, that night I was sitting looking at some wiring diagrams which I had downloaded from the Victron website. I had used these as the basis of designing the setup in the rear of the Fiat.
There are several components not installed, like the lithium batteries, associated battery monitors, remote protect, inverter etc, but the solar, dc to dc (Orion) solar panels, -ve and =ve buses and the shunt are all fitted.
(edit) the site wouldn't let me post a link to the diagram so I made another post to hit '5' and the link is now two posts below. refer to that link and what I said in last sentence might make sense !
It dawned on me that although I had a cable running from starter -ve through the DC to DC charger to the battery negative (via the neg bus and shunt), and even though the neg bus was grounded to the chassis, there was no direct cable from the front battery -ve to the rear -ve bus - just the chassis earth. I noticed in the diagram that there was a dedicated cable going from front battery to -ve shunt in the rear.
So the next morning first thing I went out there and the same problem still existed, 7.5v between starter -ve terminal and the chassis.
I disconnected the -ve cables at the DC to DC charger and connected them together, thus bypassing it and making a clean path for the electrons to follow.
Low and behold the voltage disappeared between chassis and earth, the BMV began reading correct starter battery voltage and all the problems disappeared. Accessories on, car started fine.
So it was certainly an earthing issue, but nothing to do with the factory wiring. Luckily for us the mechanics had not started work and cost us nothing. tow was under roadside assistance.
I have since added a new cable linking front and rear -ve terminals for direct path for elecetrons to flow and have re-connected the DC to DC charger and all is good.
I still can't work out why though, when I physically disconnected everything from the rear to the front, that the gremlins remained. They too should have disappeared at that time !
Thanks for everyone's assistance on this. You all helped greatly.
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