Mysterious battery drain... where to begin?

[OrangeCrush]

Hello,

My new-to-me boat is hauled out for the winter and it seems that the house battery is draining on its own somehow. The battery monitor shows zero amps of draw when the house switch is turned off, but after two weeks or so the voltage drops from 12.8 to 12.0 or lower. The only thing I know that is hard wired is the bilge pumps which are both off.

The previous owner said that the batteries would hold a charge through the winter without being disconnected. In general the wiring is in good shape and most of it was redone 3 years ago. The batteries are 4 AGMs for 440 amp hours total. I'm sure it's not good for them to get so low, but a month ago when I was sailing they were able to maintain their charge through pretty heavy usage over the course of a weekend, so I don't think they're shot (yet). The starter battery is charged with an echo charger and is staying full. The only switch I've been leaving on while the boat is unplugged is the Main AC double breaker because the PO said he never turned it off. Could that be a factor? The battery monitor itself seems to stay on but I can't imagine that draws much nor do I know how to turn it off.

I've got a multimeter and I'm ready to crawl into whatever nook I need to crawl into, but I don't know where to start. If the battery monitor shows zero draw, I don't see how pulling fuses or disconnecting wires will help me find the source of the draw.

Here is a picture of my panels (while on shore power) Any advice is most greatly appreciated!


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[topmast]

Would a constant on volt meter account for that much drain?

[twinboat]

It seem pretty simple at first. Put the volt meter between the pos cable and pos post of the battery. If it reads anything, there is a draw.

Now unhook the small + wire to the shunt and check. If it goes to zero, you got it.

Next, unhook the direct wired pump. It could have a small draw, since it lives in water.

If you find no draw, leave the cables off for a week. If the batteries drop, time for new batteries.

[OrangeCrush]

No clue but I doubt it... It's a Xantrex Link 10 shunt battery monitor. A quick browse of the manual leads me to believe it cannot be turned off.

Two more potential clues: a yellow wire labels Ground I appears to have come loose from the voltage regulator near the alternators. I'm not sure which contact to reconnect it to, if any. (see pic)

Also, the DC outlets have been without power which I'm also working on troubleshooting.




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[OrangeCrush]

Originally Posted by twinboat

Put the volt meter between the pos cable and pos post of the battery. If it reads anything, there is a draw.

Thanks, but which positive cable exactly do I put the voltmeter on?



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[rwidman]

Batteries can self discharge on their own. To check this, charge them up and then disconnect them from the boat and from each other. Come back in a couple weeks and see if any or all have lost some of their charge.

[OrangeCrush]

Ok I will do that as well, but I can't imagine they are discharging that quickly without a draw unless they are really toast already, which I guess is definitely possible. Another potential clue: one of the batteries is heavily corroded on the negative terminal, the rest look great.


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[Jim Cate]

It seem pretty simple at first. Put the volt meter between the pos cable and pos post of the battery. If it reads anything, there is a draw.

Umm... this does not make any sense. A voltmeter between the pos battery post and the positive cable should read zero, because there should be no voltage drop between them... even if there were a significant current flowing.

Perhaps you meant he should disconnect the cable from the battery and then, having set his multi meter to an AMPERE scale, connect it between the two points. That would indeed measure any current flowing. I'd start out on whatever the highest ampere scale the meter offers, and if nothing shows, work down to the most sensitive scale. Do be careful NOT to get the meter between a positive point and ground. The ammeter is essentially a short circuit, a large current will flow and the meter will be toast (some have a fuse in that circuit, and it may save the meter. Still not a good idea!).

Jim

[OrangeCrush]

Originally Posted by Jim Cate

Umm... this does not make any sense.

Jim

Yeah I was confused by the positive to positive idea, but disconnecting them and testing the gap makes sense.






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[twinboat]

Disconnect them all, put each pos to the meter while the other lead in on the battery. The one that reads any volts is drawing something.

That's the one to follow-up on.

[Time2Go]

YouTube
Parasitic Power Drain
and you will find many videos on how to diagnose
Took me two batteries to find out that the interior
trunk light was not shutting off when I closed the trunk.
Mostly auto oriented but the technique is the same
Cheers
Neil

[DeepFrz]

That battery with the corrosion is probably toast and it pulling down the other battery. Disconnect them and check the voltage of each battery.

A little more info on how you charged the batteries when running would help. What voltage, how long, current and voltage just before you discontinued charge, etc.

Don't count on your Link 10 to tell you when the batteries are fully charged. Read the article on Compass Marine web site about battery monitors.

[Steve Bean]

I've heard of bilge pumps that come on every so often to test for water and keep pumping if there's water, or shut off if no water. I don't prefer this kind of pump. Do you have one of these?

[carambo46]

What Jim said you'll find out within 5 minutes if you have current drain with an amp meter not a voltmeter and most will tell you use the negative battery post to decide amperage flow

[OrangeCrush]

I pulled off the large positive house cable and tested the gaps between the three positive cables on the terminal there. The biggest (house) cable showed nothing. The cable to the echo charger showed a draw of about 3mA and the charger started blinking when I did it. Then I tested the smaller cable marked "unswitched panel" and it showed a rhythmic fluctuation between 30 and 60 mA, like a metronome. This unswitched panel wire is going to be very difficult to follow, but obviously I need to figure out where it goes. Does this sound like a short circuit somewhere? What would do this? I don't know what else is on unswitched panel but I pulled the fuses from the bilge pumps so it shouldn't be that.

It sounds like good news for my battery bank but bad news for my overall understanding of what's going on.

As always, I really appreciate you taking the time to share any ideas or guidance.


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