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Old 24-04-2010, 01:09   #1
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Mystery Electrical Issue...or Not ?

Alright, I am into week two of my first boat owning experience...

I am a liveaboard and spend 99% tied to the dock connected to shore power.

I periodically have a look at my gauge, in the past I have always seen the needle pointing in the "charging" range of "13-15 volts"

Tonight when I got home I noticed the gauge was below the charging range and was showing 75% battery power. After looking around hoping to see something obvious, I checked the shore power cord at the meter on the dock and found it to be slightly loose, so I pushed the cordinto the socket a little tighter. I then came back in and found no change on the gauge. After a couple minutes of literally staring at the charger & batteries I looked again to see the needle on the gauge back in the charging range.

I had figured that the cord I tightened outside was indeed the problem and it probably just took a couple minutes for things to get right again...


A few minutes ago I looked again and it was back below the charging range in the 90% battery power range....

and thats when I started typing this post. Just now I looked and it was back in the charging range.

SO, my question is, Is it normal for the gauge to read this way? Does it only stay in the charge range for a short time, then allow the batteries to run down slightly and then charge them up a few minutes later?

According to the amperage gauge I am drawing a total of 1 amp right now, and have been drawing no more than 2 amps during the fluctuation.

THANKS!!!
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Old 24-04-2010, 09:20   #2
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What brand (and age) is your charger? How old and how many amp-hours is the bank being charged? Some more details on the gauge?
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Old 24-04-2010, 22:33   #3
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The charger and batteries are a few years old. It is a Xantrex charger. Im not sure of the details on the batteries though, they are unmarked.

I do not know the amp-hours, how can I determine this?

the gauge is an analog gauge, the only markings are "Professional Mariner Ventura, CA"

Thanks
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Old 24-04-2010, 23:18   #4
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Are they led acid batteries? they may need a top off with distilled water only. My battery charger lasted 5 years and when it finally went out I got a reverce polarity light on the A/C panel.
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Old 25-04-2010, 02:56   #5
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Yep. Start with topping them up ASAP.

And since you're new, always start at the cheapest spot first. I know that rule very well. Don't always remember it until....

Just start at the cheapest spot first.
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Old 25-04-2010, 03:59   #6
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Yep. Start with topping them up ASAP.

And since you're new, always start at the cheapest spot first. I know that rule very well. Don't always remember it until....

Just start at the cheapest spot first.
I have never heard this rule before. What does it mean and what are the consequences if it is not followed?
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Old 25-04-2010, 04:31   #7
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I have never heard this rule before. What does it mean and what are the consequences if it is not followed?
It sounds like a modern version of Occam's Razor - "Given the choice between equally probable hypotheses, always choose the simplest".

When I was a "new" driver my engine started making horrible squealing noises one day. Lacking a lot of money and lacking even more knowledge about car engines, I worried and worried about it and how to fix it myself. I had visions of seized pistons or bits of metal rubbing together. Eventually I got a mechanic to look at it and he tightened the fan belt.

Left to to my own devices, I would have had the top of the engine off. The mechanic's fee was to have a good laugh at my expense - and a six pack of beer.

For shibbershabber, some distilled water for the battery is a good starting point. Much cheaper than starting with battery replacement, even if it doesn't work.
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Old 25-04-2010, 05:00   #8
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I have never heard this rule before. What does it mean and what are the consequences if it is not followed?
Well, it's not a joke. It's a real principle of working on complicated mechanical things.

When a complicated mechanical thing malfunctions, there are two activities involved in solving it: (a) diagnosis, and (b) cure.

Diagnosis is very often not worth the effort. It often costs more to perform the tests necessary to determine the source of the fault, than it does to cure the most likely culprit.

Mechanics often exaggerate and abuse this, by the way, just replacing things willy-nilly without investing even a little investigation and thought into understanding the fault. This is also wrong, but even a perfect mechanic will often start replacing things before it is clear what the fault it, because this is the rational and most efficient course of action.

So the principle of "start wih the cheapest spot" comes into play when you've done the appropriate amount of diagnosis and analysis and you've narrowed it down to a couple of things. That squeak in the example above is an extreme case -- it's either a fan belt or a spun bearing. You have done all of the diagnosis which is reasonable under the circumstances, so what do you do next? Of course, you go first to the cheapest spot -- the fan belt.

If you adjust the fan belt, and it turns out that was not the problem, then you're only out five minutes of labor and zero parts. And you go on to tear the engine down after the spun bearing. If you do it the other way around, you run a serious risk of wasting not five minutes of labor and zero parts, but thousands.

So naturally, you start at the cheapest spot.

I think Zen and the Art of Motorcycle Maintenance has a chapter on this, if my (somewhat spotty) memory serves.
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Old 25-04-2010, 06:16   #9
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I have never heard this rule before. What does it mean and what are the consequences if it is not followed?
Yep. All of the above.

What are the consequences? Short answer- trashing of boat bucks, AKA-expensive education.

Now that you have learned the rule, you are no less vulnerable to forgetting it.
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Old 25-04-2010, 06:20   #10
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Do you have any way of checking to make sure the dock power is on?? Sometimes the on-again-off-again charging is the dock power cutting in and out. If you don't have an AC voltage meter, something plugged into an outlet will do.
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Old 25-04-2010, 09:01   #11
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The 90% rule & look for the last human touch...

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Diagnosis is very often not worth the effort.
This sounds a little to simplistic. I agree that diagnosing something until you are 100% sure of the problem is expensive and often impossible. I find that if you get to the point where you are 90% sure of what the problem is then change the part. This takes 1/4 the time or less than the 100% method. It also generally saves you money.

Most importantly the first place you should look is where a human was last. Quite often you will find that where someone was last is your problem.
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Old 25-04-2010, 11:33   #12
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Most importantly the first place you should look is where a human was last. Quite often you will find that where someone was last is your problem.
Excellent advice..
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Old 25-04-2010, 12:02   #13
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I agree..

James S.. very funny quote from Opie91. Shibbershabber. I would not worry to much unless the batteries are showing a significant drop in power (like 60% or less). Plus am not sure what to think to draw a better conclusion because of factors not presented such as:

Solar panels?
Regulators?
Xantrex battery charger settings?
Power load drawing off your 12 volt system?

But it is good to be aware and to ask questions and search for answers. It is what makes a good boat owner and Captain. Congrats on your new lifestyle.. You will love it!

One thing I can impart to you is to be aware of marinas (when you travel) that have the shore power mis wired (such as negative and ground power being charged) this can cause reverse polarity and lead to potential voltage leaks in the water (from you or other boats) that will eat right through your shafts and props in as little as a month (galvanic corrosion). I have found this to be evident in many marinas in the Caribbean and a few in south Florida. Most were from a result of unqualified personnel wiring the docks to the main AC power source.
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Old 25-04-2010, 19:00   #14
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I would not worry to much unless the batteries are showing a significant drop in power (like 60% or less)..
Just do it.

DO worry about the water in your batteries.

Be nice the them if you want them to last. Besides, it really is most likely to be your problem.
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Old 25-04-2010, 19:48   #15
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I think there has been some great advice so far but the first fundamental question has not been answered and for those with experience I will restate it.

For those of you with shore power, a charging inverter, charging indicator, a voltmeter and an ammeter -

1 - Do you normally see short term fluctuations in charging rate?
2 - Do you see the battery power drop to 75% then climb back to 90+% over time?

Shibbershabber - I don't have such a system but the first step for me is to monitor it over time. I would not be concerned at this point unless the battery power dropped below 60%

While monitoring I would be looking for the fluctuations you describe. My premise is that the system is cycling and in my mind it shouldn't be cycling that much. The troubleshooting when you get to it is to determine why it is cycling.

1 - It's normal - the charge system is set up to discharge to a certain point and then recharge
2 - It's not normal - something is supposed to be sensing current draw and is not sensing it properly - i.e. there is a charging system problem
3 - The battery bank has a problem - low water, high resistance, some other intermittent fault or problem.
4 - There is a shore power system intermittent problem.

Part 2 is an educational exercise. I would search the internet and the docs that came with the boat for manuals on the equipment you have. Then I would read the manuals cover to cover and try and work out how the system should behave. If you didn't understand things in the manuals I would post questions here.

What you end up with is a pretty good education about how your electrical system works on your boat.

The cheap things described above are not bad things to do and many of them fall into the category of preventative maintenance.

- top up lead acid batteries
- disassemble, check, clean and reassemble the battery connections

I also generally agree to do the simple things first but it should be blended with experience. You can sink a lot of dry holes but shotgun troubleshooting and waste a lot of time.
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