I’ve got a stable 24v supply in the cab of a unimog. This is from a pair of 12v automotive batteries which enough charge to turn over the engine. And to a known good ground point on the chassis.
When I connect a Victron 24v-12v isolated dc converter it drags the voltage down to 11v. It then creeps back up to 15v over about 30 seconds, at which point the Victron undervoltage deactivates, I get a brief power flash on the Victron, and it drops the voltage to 11v again and undervoltage triggerw. It then repeats.
Disconnecting the Victron returns the voltage to a steady 24v.
This is with no load on the dc-dc convertor and the same occurs weither the remote is shorted or open.
Where are you measuring this voltage? ( the one that drops to 11V?)
This is indicating a high resistance in one of the battery leads: The current required to pull a good pair of 12V batteries in series down to 11V would melt any but 150+mm^2 size cable…
This could also be a damaged fuse in the line.
If you have a clamp meter, it would also be worth measuring the input current to the converter..
As soon as you said it, I realised that pulling down the battery voltage wouldn’t be possible from the Victron unit - I’d have a fire or be blowing fuses!
I finally got back into this and resolved it. I was using an earth point from the manufacturer, but it wasn’t as good as you’d expect. Changing earth points immediately resolved the issue and the installation is now working as expected.