Zig unit not charging leisure battery

[Big Bad Baz]

I have this charging unit:



Which, up until recently, has been as good as gold. However, it no longer appears to be charging the leisure battery. When the engine is running, there is a clicking sound coming from the general vicinity of the charger (at the same sort of frequency as an indicator) and when I switch off the ignition there's a buzzing noise which then peters out.

I'm guessing that the culprit is the "Smartcom" doo-dah in this picture (if I touch it when the ignition is on, I can feel it clicking):



Which, Google reveals, is just a fancy relay.

So, do these things just "go" and stop working, or might there be another reason for my lack of charging? At least they're not expensive to replace, if I do need a new one.

[CJH]

I'd hazard a guess that your leisure battery is past it. The smart relay works by sensing a charging voltage, so when the alternator is running the starter battery's voltage rises above a threshold, which then closes the relay so that the leisure battery gets the same charge. When the voltage drops below a slightly lower threshold the relay opens again to separate the batteries.

If your leisure battery is badly discharged then the moment the relay closes the combined voltage of the two batteries may drop below the lower threshold causing the relay to open again. It'll repeat that cycle indefinitely. The clicking from the Zig might be happening when the leisure battery is momentarily connected to the starter battery and therefore has enough voltage to power the Zig's circuits.

You need to get a meter on your leisure battery to see what state it's in when the engine isn't running. Anything less than 11.5V and it needs a really good charge at the very least.

[CJH]

Oh wait - is that the back of your Zig panel at the bottom of the battery photo? The clicking has nothing to do with the Zig then I think - it's just that relay switching in and out as I described.

[Big Bad Baz]

Thanks for that, very helpful. So, good charge of the leisure battery and go from there. We'll see.

[CJH]

Yes, give it a good charge then see what happens. If you've got a voltmeter it would be useful to know what state the battery is in before you put in on charge. If it's already reasonably charged (say 12V or above) it's unlikely that what I've described is the problem.

Also, if you find it's badly discharged and then you charge it, a voltmeter will be useful for assessing the state of the battery. If it can hold a charge of about 12.6V for 24 hours after you disconnect the charger then it's likely to be ok.