Battery Draining

mark156531

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I have a 1980 Johnson 85hp. With the engine off and the key removed from the ignition I performed some tests using a hand held voltage meter. I have found that there is .5 volts draining from the positive battery terminal to the wire going to the starter solenoid. I also found that there is .1 volts draining through the wire going to the charging system. Any thoughts on what might cause this to occur or what I should check?

Thanks
 

oldboat1

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any other source for parasitic drain? (a gps unit, possibly.) If you have power trim, there is a 30amp fuse in the system (might pull it out and test again). Also, could disconnect the rectifier wiring in case a diode is failling, and repeat your test. (Don't leave the rectifier disconnected, as you will burn it out if you start the engine that way.) Corrosion can be a culprit, so would clean all connections (battery and solenoid).

guesses....
 

emdsapmgr

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Maybe the contacts inside the start solenoid are still connected, causing a bleed off of the battery charge. Check/replace the solenoid?
 

F_R

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Would you mind telling us exactly how you are performing the tests? That is, meter leads connected to what & where? I ask because I'm thinking there may not be a problem at all.
 

Assassin3F

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That is a really small voltage draw. I think I would look at an connected accessories first...like the radio or the horn. Also make sure you have the multimeter set correctly. That bit me on the butt a couple of times.
 

gm280

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First, if you just turn on your digital volt meter and allow the lead to be open and not touching each other, what does your meter read? And if you short the two leads together, what does your meter read? I would be interested in see those reads. Also what type meter are you using, brand and model?
 

F_R

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What I was getting at when I asked my question was that the presence of a voltage does not necessarily mean there is a drain (current). Interpretation of the readings is everything. One side of a light bulb in your house may have 120 volts on it, but it is not using any electricity unless the other side is grounded.

If you really want to check for drainage, connect a amp meter (or milliamp meter, whichever is appropriate) in series with the suspected circuit.
 

Vic.S

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Talk of " voltage drain " is total nonsense.

The readings posted do not indicate that there is anything wrong at all, rather to the contrary, if they were made with a modern digital meter.

If you think there is a problem with your batteries do as F_R suggests check for a current drain with an ammeter or a milliammeter. or multimeter on an amps/ milliamps range
 
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gm280

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To try and make this a little more understandable for those that don't understand electrical things...I hope.

I will use a garden hose as an example.
If you put a pressure gauge on the end of a garden hose and block off any water coming out of the hose and then you turn the water on, you will read the water pressure in the hose but no water is flowing. Voltage is equivalent to the water pressure. A voltage reading only means the amount of voltage but no current flow. If you then remove the hose blockage and allowed the water to flow out, you could measure that amount of water in gallons over a period of time. Current is like that water flow where you can also measure the current flow using an amp meter. So water pressure is like voltage, and water flow in gallons is like current flow in amps. Hope this helps those that are not that familiar about such things. It really sounds a lot more difficult then it actual is. JMHO
 

Vic.S

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To try and make this a little more understandable for those that don't understand electrical things...I hope.

I will use a garden hose as an example.

I hate using the water analogy.

I usually offer a link to these course notes which explain the basics pretty well. http://www.tb-training.co.uk/cover.html

or suggest an elementary book such as "The 12 Volt Bible for Boats" https://www.amazon.com/12-Volt-Bible...ible+for+boats

The ultimate book is probably Nigel Calder's "Boatowner's Mechanical and Electrical Manual" https://www.amazon.com/Boatowners-Me...512726&sr=8-13 biut it is not really a beginners book.
 

oldboat1

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still out there mark? Lot's of good info. ^^

I'm guessing you probably had a reason for checking your battery or electrical system. If your battery is old, it may no longer be holding it's charge between uses -- or may otherwise not be up to use as a starting battery. Alternatively (or maybe in addition), your charging system may not be working.

As you may know, most parts stores will load test the battery for you, and check its ability to hold a charge. Additionally, it's pretty easy to determine yourself whether your alternator is supplying a charge. If you are accustomed to measuring voltage, a healthy battery with a full charge will show around 12.5 volts. Measured while underway, you should see between 13 and 14 volts if the alternator is doing its job.

If you are running a lot of electronics, you might want to look into a two bank system, perhaps with a battery switch -- lots of hands on information in the electronics section if you want to do that.
 

bruceb58

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Take off one of the battery cables. Put your meter in current measuring mode. Connect the leads between the cable and the battery post. That is the only way to see how much current you are drawing.

Measuring voltages accomplishes nothing.
 

Tim Frank

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^^^ +1

If you also (after removing one battery cable) measure from one battery post to the other, you will get either + or - 12 volts. But with no actual connection, there is no circuit.
Just because there is a voltage difference does not mean there is any current flow.

I think you are chasing your tail. :)
 

mark156531

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Thanks for all the info and suggestions. I won't be back to the boat until the weekend but here is some additional information and the method I used to get the reading. This battery is a year old and the prior battery was losing a charge as well. The only accessories are the boat lights and bilge pump. Both were off and the key was out of the ignition at the time I ran the test. I disconnected the positive leads on the battery. I then connected the meter between the positive battery post and the thickest of the two red leads going to the engine. I assume this is the lead to the starter solenoid. The reading on the meter showed about .5 volts. I didn?t expect to see any indication of current if the starter circuit was open.
 

gm280

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Both Bruceb58 and Tim Frank offer good info. The only thing I will add is, don't even try to crank the engine when you have your meter in series with the battery and battery wire. Because unless your meter is capable of measuring large amounts of amps, you will toast the meter instantly unless there is a fuse inside to open the meter connection. Amp meters are connected in series with the battery or power source. But they can read 100's of amps or more. JMHO
 

bruceb58

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The reading on the meter showed about .5 volts. I didn’t expect to see any indication of current if the starter circuit was open.
You were not measuring current. Not even sure what you were measuring since you had the battery disconnected. It was an invalid test.
 

interalian

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If you were using a digital multimeter, measuring 0.5V across that circuit is just showing leakage as DMMs are very sensitive. I'd bet there's no actual current flowing if you're actually measuring volts.
 

Vic.S

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Here's a circuit diagram to help you.
http://www.maxrules.com/graphics/omc/wiring/80_81_V4.jpg

Next time you take a reading disconnect some circuits to pinpoint the problem.

Pull the fuse, disconnect the red wire from the terminal block, you get the idea.

Nothing wrong with how you're testing it, my money is on the rectifier.


But he was using a voltmeter and measuring volts. As has been explained several times above he should have used and amp meter and measured the current flow, if any in amps or milliamps.
The voltage readings he is quoting are totally meaningless.
 

Tim Frank

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Here's a circuit diagram to help you.
http://www.maxrules.com/graphics/omc...g/80_81_V4.jpg

Next time you take a reading disconnect some circuits to pinpoint the problem.

Pull the fuse, disconnect the red wire from the terminal block, you get the idea.

Nothing wrong with how you're testing it, my money is on the rectifier.

But if the OP replaces his rectifier it WON'T be with YOUR money....it will be with HIS. :) There is NOTHING in this thread that indicates a rectifier problem.:confused:
He has established neither a current drain, nor a charging issue at this point... and his methodology will not accomplish either.

Assuming you actually understand some of this, you might want to re-read the thread because you must have have missed the essence of it.

If you can then explain how the OP's comment
I also found that there is .1 volts draining through the wire going to the charging system.
is testing anything correctly, I will read it carefully, and if it is rational, I will apologise and acknowledge your superior electrical T/S skills.

Otherwise, you are simply dispensing poor, and possibly costly, advice.
 
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