Tiny Problem with my Smartcom Relay

[albertramsbottom]

Hi

First of all, thanks to everyone who helped me wire up my smarcom leasure battery - It works - Well almost

The issue is that when I have been driving my van (fridge works), there is a certain amount of residual voltage in the SB. This means that the relay takes about 30-45 seconds to turn off. But whilst its still on the van struggles to turn over. SO if I stall it then im in a bit of bother and its either wait for the relay to swich off or jump in the back and turn my fridge off.

I cant really figure this out as I would have thought firdge would be taking its power (whilst the relay is still on), from both batteries. This shouldnt make the SB not turn over the van, should it?

I have a attached an diagram of my wiring. There are two observations that I can make from this diagram and these are that

1. Should the relay's earth be attached to the starter battery, becuase it is attached to the LB currenlty
2. I couldnt work out how the switch worked on the fridge so I used a multimeter to find the live and just took it out and then ran a feed from my relay. I just taped up the old wire. So I also couldnt figure out the earth for the fridge so I just assumed that it earthed to the body somewhere.

Can anyone see anything wrong with this set up?



Cheers

PS - going to busstopover this weekend so I might see some of you there

[1664]

Although that looks like it should work on paper the 'Smartcom' relay (if I have the right type of relay) works by measuring the voltage on the starter battery which determines when to switch the relay contacts. Since the system is only 12v in the first place, even a small descrepency between the earth at the leisure battery and the earth at the starter battery can effect the voltage at the relay sensor input. Disconnect the cable to the leisure battery earth and temporarily run a cable to the starter battery, switch everything on, take the van for a run and see if that cures it. If it don't I really can't think of anything else.

As regards your fridge earth, it probably runs into a common earth connector somewhere. If it didn't the fridge wouldn't have worked in the first place.

[bigherb]

As 1664 say it would be better to connect the earth to the body or the starter battery earth, but I don't think that is the cause of the starting problem.

[AngeloEvs]

I would expect a hot engine to turn over even with fridge on given that both batteries are available to the starter motor. Sounds like you may have battery issues here or a poor earth. I would eliminate a poor SB earth by placing a multimeter (DC Volts range) across the starter battery earth terminal (the 'terminal' not the clamp)and chassis (safety Belt anchor point is convenient) with the SB under load by switching the ignition on. A good earth should result in a negligible voltage reading. If you do get a reading then the earth is poor and the higher the reading the worse the connection. As 1664 says better to earth at the source (SB). You could also re-adjust the relay to drop out at a higher voltage if yours is adjustable