Durite Smart Relay Fuse blows on start

[Titus A Duxass]

As the title says.
My Durite smart relay blows the 30 amp fuse when I start the engine.
Something tells me that the smart relay is not isolating the leisure battery when it is off.

Or am I missing something?

[slowcoach]

Does it have the led to show when it's connected/disconnected?

My solar setup actually connects the two batteries when it's sunny and the charge is 14.5v ish as it should I guess,, but even then when I start the engine it doesn't blow a fuse, guess it takes current from the most direct source (starter batt)

[ZsZ]

Probably the batteries have surface charge above the isolating voltage and that keeps them connected

Or just the relay burnt closed.

[bigherb]

Durite relays do tend to switch on at lower voltages, might be surface charges holding the relay on, unfortunately, Durite relays sense voltage from both the starter and leisure battery. What type of fuse have you used? Maxi or Midi/strip fuses are better as they have higher surge tolerance.

[Titus A Duxass]

Big Herb - it's just a standard blade type fuse.

[bigherb]

I would fit Midi fuses in any case more tolerant of surge currents. But check the Durite relay does actually switch off and it's cut in voltage with it disconnected from the leisure battery.