Power leak/short

[John7]

When I tested the power on my boat last, plugging a multi meter into a power socket, it was reading 02-3 volts with the power switched off.
I do this regularly as a way of checking the charge in the batteries, if done before any load is put on them it’s a way of seeing what there charge is like. I hadn’t noticed this reading before. I would think it must be a short in the main switch (a Guest (I think) switch))
Is this leakage worth worrying about?

 

[byron]

This may have something to do with your auto-bilge pump. Although power is switched off there are somethings like the power to the automatic bilge pump that by-pass this.

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[John7]

Thanks for reply.
I don't have one fitted. But I do have a radio/cd player wired on to a battery (its one of those that takes for ever to set up and loses all its settings as soon it loses power, something to look out for if getting one). But if the main switch is off and the radio wiring is before this I don’t see how that would give a reading past the off switch?

 

[Ray_G]

I have a similar problem, measuring 0.3 amps with everything switched off (measured through an Adverc system) and despite professional advice I have yet to locate the problem! All I can say is best of luck.

 

[bedouin]

Do you mean between 2 and 3 volts?

I think that is unlikely to be a fault in the switch - if the circuit is unloaded then that would read near to 12V.

It's possible that one of the items connected to the 12V rail has a capacitor that is slowly being discharged.

 

[John7]

Its reading point zero two to three volts. The boat had been left for 3 weeks.

 

[Joe_Cole]

I think that it is worth trying to track it down. It may be leakage causing some nasty problems somewhere which your anodes may not be protecting against.
If you can get hold of Nigel Calders book it has tons of helpful advice on this.

Good luck with it.

Joe

 

[andyball]

If you're using a digital meter....0.2 volts is probably nothing to worry about. DMM's draw so little current on the volt setting, that spurious readings like that are common, in my exp.

If you put the same meter on current setting and short it across the socket, you'll probably read zero (OK, do it in series with a bulb first, just in case.)

0.3 amps measured in series with the battery....(RayG) is another matter of course, and sometimes can only be fixed by disconnecting everything,one thing at a time, 'til the current stops.....not hard,but can be time-consuming even on a car/bike,never mind a boat.

 

[bedouin]

Oh - in that case I don't think there's anything to worry about. DMMs typically have input impedance in the mega-ohm range - so if it is 'leakage' across the switch it is still in the GigaOhm resistance.

Any current being lost would be insignificant.

It's possible that the voltage is coming from somewhere else - e.g. a thermocouple somewhere.

 

[oldsaltoz]

G'day John,

a common cause of low level leakage is the battery top, try giving it a good clean and

a spray with some dewatering agent (CRC or WD40) and check the reading again.

Hope this helps.

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