Electrical Problem

[cajun ben]

When I remove connections from my postive battery post an read between postive. post and starter cable I read full voltage.Thats with no other connections on the postive post...have a 115 Mariner 1995.I know some accessories feed off this starter cable also.Is this normal or what.where should I start checking?

Any help is appreciated

Thanks Big Ben

[Fishing Rhino]

It's not normal. When everything is turned off, you should get no reading on your voltmeter.

Disconnect the accessories wiring, then check check each of them, including the starter circuit to determine which is drawing power. If it's the accessory feed, you'll need to see where that wire goes. It will likely go to some type of distribution panel, like a buss bar. Each cable at that distribution center will need to be disconnected and checked with a voltmeter to find which is the closed circuit.

On some boats, prior owners who are do it yourselfers, may have wired in various accessories resulting in wiring that resembles tangled spaghetti.

You should also check to see what that circuit is drawing for amps.

[Team_Dougherty]

It's not normal. When everything is turned off, you should get no reading on your voltmeter.

I am not sure if this is a correct answer.

He is connecting his voltmeter in series with his circuit. A voltmeter is normally used in Parallel with a device in the circuit.

When you hook a meter in series, like you are, in a circuit you are measuring current.

What are you trying to do?

[Fishing Rhino]

I am not sure if this is a correct answer.

He is connecting his voltmeter in series with his circuit. A voltmeter is normally used in Parallel with a device in the circuit.

When you hook a meter in series, like you are, in a circuit you are measuring current.

What are you trying to do?

I read his first post like this. When he disconnects the cable from a battery, then connects a voltmeter to the post and the disconnected cable he is reading full voltage. Full voltage can be 12+ volts to 13+ volts, depending on the state of the battery/batteries.

I'm not sure what you mean by parallel? Parallel as I understand it means batteries hooked up positive to positive, and negative to negative which means they will still produce the same voltage as a single battery but will have, an amp hour rating equal to the sum of the two batteries.

Voltage is tested, at least as I understand it by contacting a live circuit to a ground. It may be across the two posts, negative and positive, or across any circuit to ground.

With everything turned off, there should be no draw on a battery, since all circuits should be "broken". That he gets a reading shows something somewhere in the wiring on the boat there is a closed circuit.

Maybe I misunderstood the first post, but in reading it over a few times, it seems to me that he is using the voltmeter to bridge the gap between the cable and the post from which he removed it.

[Team_Dougherty]

Maybe I misunderstood the first post, but in reading it over a few times, it seems to me that he is using the voltmeter to bridge the gap between the cable and the post from which he removed it.

This is how I took it as well.

Except, in this configuration, with the meter in series with the circuit, he is measuring current. Also, most motors and boats, will have some kind of parasitic drain even with the motor off. This could be a radio keeping memory, a bad voltage regulator, a bad something or another. you get the idea. With the meter in series, to measure current, and set to voltage I am not sure what the reading will be.

a nice read http://www.sparkfun.com/tutorials/202

[Long Mike]

This is how I took it as well.

Except, in this configuration, with the meter in series with the circuit, he is measuring current. Also, most motors and boats, will have some kind of parasitic drain even with the motor off. This could be a radio keeping memory, a bad voltage regulator, a bad something or another. you get the idea. With the meter in series, to measure current, and set to voltage I am not sure what the reading will be.

a nice read http://www.sparkfun.com/tutorials/202

X2. Voltage is always measured in parallel with the load. Current is measured in series.

[Team_Dougherty]

When I remove connections from my postive battery post an read between postive. post and starter cable I read full voltage.Thats with no other connections on the postive post...have a 115 Mariner 1995.I know some accessories feed off this starter cable also.Is this normal or what.where should I start checking?

Any help is appreciated

Thanks Big Ben

Ben,

What is it you are trying to measure? Maybe we can help you.

[Fishing Rhino]

I'm going to need more tutelage as to the parallel and the series thingy. For the sake of discussion let's say we have a circuit to power the running lights, and that circuit is connected to the battery post with an alligator clip. The lights are turned on to complete the circuit. We disconnect the alligator clip, and then close the circuit using a multimeter. If it is set to voltage, will it not give us the voltage of the battery, or will that be affected by whatever components are on that circuit? If we then switch to amps, it should show us the amount of current being drawn by the lights.

I'm viewing the circuit in question as a "jumper cable" of sorts. The only bugaboo I can see to that scenario is that the resistance in the components might cause a voltage drop, and therefore not get an accurate reading of the power source voltage.

I understand the possibility of a parasitic drain, but that is usually minute and a battery in good condition should power those devices for several weeks if not months. That's why I told him he should see what the closed circuits are drawing for amps.

[Long Mike]

Tom,if you complete the circuit in the manner you described, then you need to have your meter set to measure amperage. In the circuit you described, if you leave the alligator clip connected to the battery and then measure the voltage between the ground and positive terminal of the battery you will get the voltage of the battery, less the voltage drop across your load. In other words, if a fully charged battery has say 12v when not connected to anything, but say 9v when your lights are turned on, that means that your lights, and the wiring in between, are causing a voltage drop of 3v.

[Team_Dougherty]

I'm going to need more tutelage as to the parallel and the series thingy. For the sake of discussion let's say we have a circuit to power the running lights, and that circuit is connected to the battery post with an alligator clip. The lights are turned on to complete the circuit. We disconnect the alligator clip, and then close the circuit using a multimeter. If it is set to voltage, will it not give us the voltage of the battery, or will that be affected by whatever components are on that circuit? If we then switch to amps, it should show us the amount of current being drawn by the lights.

In this instance, yes, you will see battery voltage. in the OP instance with other loads in series and parallel it will be hard to tell what you will be reading.

[Long Mike]

SWMBO sidetracked be for a while. To continue, Let's say you have a bunch of leads attached to your battery, but everything is supposed to be turned off. You know that your fully charged battery, with nothing connect to it, measures say 12v. If you connect your volt meter across the battery terminals and read anything less than 12v, then you know that something is NOT turned off. Then you have to begin your search for the culprit. I would caution that fully charged battery voltage varies, so you have to establish that baseline before you start your search.

[BKeith]

Not sure where the idea voltage is always read in parallel came from. If you know what you are doing, it's used either way. All a volt meter is doing is measuring the difference in potential, this can be what you are calling in series or in parallel. Read the voltage drop across a resistor or checking for bad connections you read them in series, measuring the same wire across a connection. Fishing Rino had it right to start with before the water got muddy.

If you want to check a battery to see it there is a drain on it, you can take a cable off and measure between the battery terminal and the wire you took off. If there is a drain, you will read voltage, if there is no drain, you will not. This is a very common method for trouble shooting a problem, while the meter is connected in series with the cable and battery and it's reading voltage, you can just start disconnecting accessories and other wires until you find the one the makes the voltage go away, you just identied the source of the drain. Not everybody understand current drain and don't really know how to use the current function of a amp meter plus, not all meters have the current function and the fact that sometimes the drain can be more than the meter will handle so you use the voltage function as this poster is doing.

Now, for the posters first, original post, what that is telling you is you have something is probably draining the battery. If you have accessories connected to the starter cable, start disconnecting everything going to that starter cable until you see the voltage go away. If you have nothing but the starter cable and still reading voltage, there's possibly something going on with the solenoid

[Team_Dougherty]

Not sure where the idea voltage is always read in parallel came from.

That is how you and always measure voltage. Even in the original posters connection The voltmeter is in parallel with battery and that is what he is measuring.

You are correct if there is voltage there is something compleating the circuit to ground. This could be the computer in the motor, they always draw current as long as they are hooked to a battery.

The best thing he can do is measure the current draw and find out if it is within exceptable specs for the motor.

[BKeith]

Call it what YOU like, no matter what you want to call it, you are measuring the difference in potential. Why try and confuse the poster with terminologies when what he is doing is a very common and often used method of checking for a drain on a battery. NO, with this method he can't tell how much drain there is. It could be a few milliamps that would never be noticed by the battery, and it could be enough to run it down in just a few hours. He can still start disconnecting until he finds the source of the drain. Another little indicator is when you put the cable on, if there a small arc, then the drain is pretty substantial. Using the voltage function lets you see there is a drain, using the current function (if the meter has one) lets you see how much of a drain (provided it's not more than the meter will measure).

Fishing Rhino gave the guy good advise without trying to confuse him with a whole bunch of what he should, could do and telling him all this other stuff, when the method he is using is perfectly good. Just help the guy with the method he is using and if you don't understand electronics enough to know what he's doing, don't try to confuse him with a whole bunch of other hog wash.

[Team_Dougherty]

Just help the guy with the method he is using and if you don't understand electronics enough to know what he's doing, don't try to confuse him with a whole bunch of other hog wash.

I am trying to help they guy. I do understand what he is doing. I was trying to make sure he understood what he is doing. It is not hog wash.

Using voltage is not the way I would do it. Current is better. IMHO.

[BKeith]

Cajun Ben

Read the very first reply from Fishing Rhino and listen to what he has to say, he is giving the proper advise. Just about everything after that is only going to confuse you.

As his last line stated, a current reading will tell you if you have enough of a draw to bother with, but that's the only benifit of doing one. Most of the rest is only going to confuse you.

[Wayne P.]

You are making all of this more difficult than it needs to be.

What you have is a closed circuit somewhere. To find it, remove the positive battery cable. Put one meter probe on the NEGATIVE battery post and the other meter probe on the positive battery cable. Set the meter to read OHMS. If the meter has a beeper, use that instead of looking at the ohm readout. You will be using the meter battery for testing instead of the boat battery. That is a lot safer and easier than all the decribed procedures.

Then do the disconnection of each device or switch until you don't hear the beeper or you don't get an OHM reading. Whatever you disconnected to get the above is your problem.

[BKeith]

No, actually you're the one making it more difficult. Now you are throwing using the ohm function in. That's even more difficult for a beginner.

Fishing Rhino gave him good advise, you told him he didn't know what he was talking about. I agree with Fishing Rhino so now I don't know what I'm talking about. I guess in my thirty years of electronics, and many years of trouble shooting vehicles, industrial equipment and boats, I never understood what I was doing, yet all my customers have always thought I was extremely good at it. Using continuity is about the hardest what for a beginner to check it. The only time I use continuity is when the draw is so great, it's blowing the fuse. Actually, I rarely use continuity then because I have $400 circuit tester I can hook in line and see and follow a short or open all the way to the source with a toner wand.

Oh, by the way, even if it's blowing the fuse, all you have to do is leave the fuse out and connect a light bulb of the proper voltage across the fuse terminanls. The light bulb light up until you disconnect the wire causing the voltage. If the draw is not enough to light the bulb, try a small one watt bulb. If it that burns dim, then the draw is probably not enough to cause any problems. See, don't even need a voltmeter to troublshoot the problem. A little 12 volt bulb will do everything he needs to do by connecting it between the battery and the cable. He just disconnect one wire at the time until the bulb goes out and then see what that wire goes to.

See, you don't have to make it no more complicated than a little 12 volt bulb.