Victron Isolated 24-12v convertor drops supply voltage

DIY
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1

Anyone heard of this problem?

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.

2

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..

3

You say a stable 24V power supply, is this a regulated power supply, if so then what is the capability of it.