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  #1   IP: 98.204.107.165
Old 07-18-2016, 09:10 PM
cfergu22 cfergu22 is offline
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Batteries draining, Multiple Electical Mysteries

To start this post off, This is my first major electrical problem on the boat since buying it 4 years ago. I know the basics and in the past few days have read as many of the posts on alternators and batteries I could.

Background...
Last week, after 1 hour of motoring then a 5 hour sail with radio and depth finder on the engine started up but blower was weak. Upon picking up a mooring ball, and shutting the engine down, both our batteries were dead. We have a battery selector and had it set to both all day. That's how we've used them for 4 years based on the PO's suggestion. One battery was 5+ years old and one was 2 years old.

The next day we got a jump, motored into a slip, charged the batteries and started troubleshooting. The oldest battery wouldn't take much of a charge and would die below 8 volts as soon as any load was pulled from it. This measuring was taken with a multi meter at the battery posts. We just considered that battery to be dead so we removed it from the boat. The newer battery would read around 12.5 volts after 12 hours of charging then I started the engine once, shut the engine off let the battery sit for a few minutes and it would be reading around 11.7. The next start up was very weak. We figured the oldest battery had weakened the newer battery. We also noticed the alternator was only outputting 12 volts at half throttle. That measurement was taken with a multi meter at the alternator. We needed to get home and wanted to be confident in our batteries so we replaced them with 2 new batteries (group 24 lead acid, one is a starter the other is starter/deep cell). I charged them up for a few hours with my 2 year old ProMariner ProSport 2 bank battery charger. We were going to get the alternator rebuilt when we got home. But we're still seeing a problem, we haven't fixed the alternator yet but I think this is a bigger problem than the alternator.

We took 2 sails since, different days, after full charges. Around 5-30 minutes of motoring and 2-3 hours of sailing with just the depth finder on. We're keeping the batter selector on 1 battery at a time now. Both times, the selected battery died after an hour or so of sailing, different batteries each time. I'm assuming based on our previous experience that you can sail with the depth finder on for a long time without draining the battery, we've done 6 hour sails with radio and depth on with no noticeable loss.

So I charged the batteries up and tried to do some more trouble shooting. The only odd thing I have noticed is that when the batteries are at rest, fully charged they read 12.6-12.7. When you turn the battery selector on to either battery they immediately drop down to 12.1 even though the ignition isn't on and no electronics are on.

Here is the only piece of out of the normal info that I think could be of help. The PO installed a macerating toilet that doesn't run through a circuit breaker. Right when I turn the battery selector on the toilet can operate. So technically, it's the only thing getting power when I switch the battery on.

So what should I be looking for? Should the batteries drop to 12.1 when I turn the battery switch to on even though no electronics are on? Could voltage just be leaking out somewhere? I've used 2 different multi meters to do my testing so I don't think I have a problem there.

I just need some guidance as to how to start troubleshooting this one.

Sorry for the long winded start but there are a lot of pieces this the puzzle.
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  #2   IP: 32.211.28.40
Old 07-18-2016, 10:23 PM
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Al Schober Al Schober is offline
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You've definitely got a gremlin eating at your batteries. 12.6-12.7 full charge at rest is good, dropping to 12.1 is very bad. You've got something that's sucking the life out of your batteries.
First thing I'd do is disconnect all the loads that don't go through your electrical panel. Not being able to shut things off isn't good.
You're going to need some way to measure the current being drawn from the battery, or at least tell if current is being drawn. Cheapest way is with a small 12V light bulb, perhaps with alligator clips. Open a connection, attach the bulb, and if the light goes on it's drawing current.
Start with a bare battery terminal and check the lead to the main panel with all switches off. Is the bulb on or off? Continue from there checking individual circuits. You'll find it..
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  #3   IP: 71.178.82.219
Old 07-18-2016, 10:33 PM
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sastanley sastanley is offline
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cferg, Here is my guess...the bad battery sucked down the good battery. P.O.'s don't always know everything. I NEVER run on "both" unless I am trying to emergency start the motor after my house bank fails to start the motor...and even then, I would switch to the start battery by itself, in case I am having some trouble with the house bank.

I've had some batteries last for 7-8 years, and one last for 2-3 years. I go to WalMart and buy the simple lead-acid kind. I have two Gr 29's for the house and a Gr 24 for the start.

I also have two small solar panels that are connected to each bank with a regulator for each and I have no shore power at the dock.

I like Al's' test, but I would charge them with a good charger, disconnect them from everything, and then see if they will keep 12.6-12.7v at rest for a few days.
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Last edited by sastanley; 07-18-2016 at 10:39 PM.
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  #4   IP: 24.152.132.65
Old 07-18-2016, 11:16 PM
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ndutton ndutton is offline
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Excellent advice but you should be looking in three different areas as you chase this down: battery condition, charging system and unintended electrical drain.

Battery Condition
Shawn's advice is spot on, disconnect the batts, charge them up and let them sit for a couple of days before testing voltage. When was the last time the water levels were checked? Probably should top them off before charging. Your local auto parts boutique can perform a simple load test on the batteries too. I have a feeling they're done.
.
Charging System
If you're not getting between 13.8 and 14.4 volts out of the alternator with the engine running at least at 1000 RPM, there are charging system problems. If correct, this may have caused battery damage regardless of battery age.

Unintended Electrical Drain
Al covered that pretty well. Anything I might add would be a repeat.
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  #5   IP: 108.31.90.116
Old 07-18-2016, 11:22 PM
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edwardc edwardc is offline
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Its possible you have a shorted diode in the alternator. This would explain both the power drain when the battery switch is turned on, and the poor alternator output.

With that much power being drawn, it should be producing enough heat to feel. With a cold engine, turn the battery switch on and feel the alternator after a few minutes. If it's warm, it's your culprit. The shorted diode will feed full battery power directly through some of the stator windings.
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  #6   IP: 98.204.107.165
Old 07-19-2016, 01:56 PM
cfergu22 cfergu22 is offline
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Thanks for your help everyone. I used some of those ideas and I think I have it figured out.

I found a loose wire that was not run through a circuit panel, it had shorted out and was melted to a ground wire. Pretty dangerous. When I took that wire out of play the voltage drop stopped. So I spent some time cleaning up wiring and seem to be in pretty good shape now.

The alternator was also bad but not the cause of the voltage drop, I took it to a shop and it came up completely dead on his bench. I'm going to have it rebuilt.

While the alternator is getting rebuilt, can I safely go out for a day sail? Only 15 minutes or so with the engine running. Is there a problem running the engine with no alternator connected to it?
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  #7   IP: 71.118.13.238
Old 07-19-2016, 02:05 PM
Dave Neptune Dave Neptune is offline
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cfurgo, IF your batteries are OK you can run for a considerable time. I ran home on depleted batteries from Catalina a 5 hour run after two days at the island using what we used power wise. I started the engine with a broken fan belt using the house side still and we used the engine, VHF, GPS, stereo, autopilot and pumped the head on the way home.
The next day I brought down a new fan belt and she still fired on the house batteries.

Go 4 it if there OK.

Dave Neptune
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  #8   IP: 206.125.176.3
Old 07-19-2016, 02:38 PM
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sastanley sastanley is offline
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cferg, I have also run for at least an hour with no alternator. I suspected a bad alternator was over charging my batteries because the meter was reading something crazy like 17 volts of output! The boat was an hour from her slip, so, I disconnected the alt., and motored home while constantly monitoring the battery voltage and had no troubles at all with the voltage loss of the batteries being negligible (my boat has EI..not sure if points draw more current.) When I got the boat to the slip and access to more tools, it turned out I had a bad meter and the alt. and rest of the system was fine. - As Dave Neptune noted, the engine itself draws very little current.

I would confirm that the batteries themselves are OK...if they won't hold 12.6 volts at rest for a period of time, they may not stay up long enough to start the motor for the trip home...but it does sound like you found a possible issue and have made corrections..let's just hope the short/drain issue hasn't been around long enough to drag the batteries low enough to ruin them. Excessive drain (below 50%, which is something like 12.1 volts on a meter) & repeated drain, while failing to recharge fully, as we now have a 2nd issue with a bad alternator) can kill an otherwise healthy battery. Keep in mind a 12v battery is really fully charged at 12.6-12.7 volts, as each cell is approximately 2.1v and there are 6 cells in each 12v battery.

Your situation is one reason many of us like a voltmeter in the cockpit, and/or in the switch panel down below. As long as I see something around 13v in my ignition circuit in the cockpit, I know the alt. is working. I have a more detailed sweep style meter in my boat panel that I can also use to check each bank. This measures battery voltage at the panel input, which is just a few feet with 4 gauge cable from the batteries, so usually I cannot detect any loss...

If you have the original Motorola alternator, their regulated output is ~13.8v & most experts recommend 14.1-14.2v (even as high as 14.4v) for charging lead acid.. If you want to get into more specifics since you are paying to get the alternator fixed, you may see if they can change regulators, or adjust the one on the alternator, and/or ask them to tell you the output voltage, so we know what you are working with. I don't want to get too far into the weeds at this point, and this opens up all kinds of other cans of worms..but we can go down those rabbit holes if you want..

If you want to read more on the subject, I found batteryuniversity.com to be a good resource, and there are many others.
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Last edited by sastanley; 07-19-2016 at 03:31 PM. Reason: correcting errors, provide link
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  #9   IP: 67.237.237.64
Old 07-19-2016, 03:07 PM
toddster toddster is offline
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Glad you found that short. I just had a dead battery problem yesterday, along with a couple of other mysteries, all unrelated, that fooled me for a while. (Cockpit instrument panel light switch got left on for a week.) It made me start thinking about moving up the ammeter shunt project on the priority list, though whether I'd have noticed that tiny draw, I don't know.

ANYWAY, the reason for my reply is to note that after I plugged in the shore power, and the charger started automatically recharging the dead battery, a couple of odd cautionary things happened. The small lengths of wire between the charger cable jacket and the battery posts, including their individual fuse holders, got very hot, and actually started producing a tiny bit of smoke. Which I wouldn't have noticed if I didn't have all the hatch covers off. I think the smoke was because the charger cable was twisted, so that the hot sections of the + and - wires crossed and touched each other. Where the wires touched, it probably exceeded the heat rating of the wire.

The other thing I noted was that, even though this is supposed to be a (ProMariner) dual-bank charger, the other battery went into "overcharge" range while the dead one was drawing heavy current. (Hydrogen gas over hot wires. Outstanding!)

It has probably done this before, behind closed hatches, while I was blissfully ignorant. Moral of the story: It's probably safer to at least partially charge a dead battery with the engine. It seems as if the charger wires are engineered without a large safety factor at the high-amp end of its operating range.
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  #10   IP: 70.192.15.215
Old 07-19-2016, 05:17 PM
tac tac is offline
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More Ammeters.....

The resolution of an ammeter, as opposed to its accuracy, is an important consideration. The resolution of an analog ammeter is in large part dependent on the meter scale and how good your eye is. For example, few can see a one amp change in a 0-100 amp meter face, so if a 1A incandescent light were the only thing left on it would be difficult to see on an analog ammeter, regardless of how accurate the meter is.

But a digital meter is different. If chosen correctly, its resolution can allow you to see an LED light drawing .1 amp (100mA). For example, I have a Blue Sea 8236 digital ammeter with 500 amp shunt. The four engine gauges and compass light are on the same circuit and draw .27 amps (270mA). All have LED bulbs. This shows on the ammeter as a 0.3 amp load.

The 8236 has an accuracy of .5% of reading. Thus its accuracy for 500 amps is 2.5 amps, or if measuring 1A its accuracy is .005 amps (5mA). But its resolution is .1A (100mA). That is, the meter's A/D converter can resolve and the meter display, from -100 to 500 amps, one part in 6000 (.1 amp out of 600 amps).

This ability to display small currents means that the power the 8236 itself uses may be measured and displayed. And with three display brightness levels, you get three different readings. The answer to this is to connect the meter's power return directly to battery return, so its current doesn't pass through the shunt.

While the digital ammeter with shunt is more expensive than the analog meter and shunt, if you need to see small currents, the digital meter is the cat's meow.
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