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Thread: Automotive Electrical Question

  1. #1
    Senior Member NAPOTS's Avatar

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    Automotive Electrical Question

    I have what I think is a parasitic current draw on my boat that is slowly draining the battery.

    I don't really have any experience troubleshooting electrical issues. I read that I should pull the negative cable off of the battery and measure the current between the cable and the negative terminal. I am measuring about 1.5 mA.

    It doesn't seem to me that this would be a very significant current draw. If I am doing my math right that is about 1 Amp-Hour per month.

    Right now I have it on a float charger.

    Is there something else I should take a look at?

  2. #2
    Team Guns Network Silver 04/2013 alismith's Avatar

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    Not sure how to find the source of the current draw, but if you can't find it, I'd suggest putting a heavy-duty, inline cutoff switch in one of the cables coming off the battery. Turn it on when using using it, and turn it off when storing the boat.
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    Senior Member whiskeyman's Avatar

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    Does your boat have a clock?

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    Senior Member NAPOTS's Avatar

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    Quote Originally Posted by whiskeyman View Post
    Does your boat have a clock?
    Nope.

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    Team GunsNet Platinum 02/2015 davepool's Avatar

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    I had the same problem with my boat. Not a heavy power drain but if i let it sit for 4-6 weeks the batteries would drop to 11 volts. Had my son in law check it out and he couldn't find any thing, i broke down and took it to the Mercury dealer who ran a full check on the electrical system and said everything was fine but the clock and the on board battery charger were drawing off the battery all the time and that might be the issue. I had them install a power cut-off switch in the battery compartment.

    As i was paying the $275 bill, i realized all i needed to do was disconnect the battery cables, but now i have this cool looking switch

  6. #6
    Senior Member JTHunter's Avatar

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    You might have something electrical that is grounding out to the water. Or is this drain on your battery still occurring when it is out of the water?
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    Senior Member NAPOTS's Avatar

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    Quote Originally Posted by JTHunter View Post
    You might have something electrical that is grounding out to the water. Or is this drain on your battery still occurring when it is out of the water?
    It is draining when it is out of the water.

    I thought about the switch or disconnecting the cable but that's kind of a pain in the ass and odds are I'll forget it right before the boat is going to sit for a long time.

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    Guns Network Lifetime Member #2

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    Radio or depthfinder? Anything electrical?

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    Team Gunsnet SILVER 05/2012 deth502's Avatar

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    not super familiar with boats but it should have a fuse box (assuming its a larger boat). check the draw, start pulling fuses one by one. when the draw goes away, thats the circuit thas pulling power. that said, 1: for a car (a boat is not an automobile, btw) <2mA is nothing, and 2: as others have said, battery disconnect is the best way to go.

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    Team GunsNet Silver 03/2014 sevlex's Avatar

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    I had in issue like this with my truck. The battery would run dead in 24hrs if undriven. It turned out that the culprit was the usb charger I had plugged into the power port (which was unswitched).

    I replaced that with a usb charger with a power-switch and turn it off whenever I park the truck. No problems since.
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    1.5ma is almost nothing, that said if there are fuses you can check, you can find the guilty circuit that way. I'd just diconnect the bat from the boat.
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    Senior Member NAPOTS's Avatar

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    is checking it the way I did the right way? regardless of which circuit it is on the small current draw doesn't seem significant enough to drain the battery.

    Is leaving it on a float charger a bad thing?

    I've noticed that it kicks on momentarily every so often.

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    is checking it the way I did the right way? regardless of which circuit it is on the small current draw doesn't seem significant enough to drain the battery.
    to check for overall draw, yes, specific circuit daw no, you need to check each fused circuit

    Is leaving it on a float charger a bad thing?
    no, this will max out battery life

    I've noticed that it kicks on momentarily every so often.
    this means it will likely never overcharge the bat, a good thing

    “The two enemies of the people are criminals and government, so let us tie the second down with the chains of the Constitution so the second will not become the legalized version of the first.”
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    Senior Member NAPOTS's Avatar

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    Quote Originally Posted by 5.56NATO View Post
    is checking it the way I did the right way? regardless of which circuit it is on the small current draw doesn't seem significant enough to drain the battery.
    to check for overall draw, yes, specific circuit daw no, you need to check each fused circuit

    Is leaving it on a float charger a bad thing?
    no, this will max out battery life

    I've noticed that it kicks on momentarily every so often.
    this means it will likely never overcharge the bat, a good thing


    Thank you! I hate asking these types of questions given my profession.

  15. #15
    Team GunsNet Platinum 02/2015 davepool's Avatar

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    Quote Originally Posted by NAPOTS View Post
    Thank you! I hate asking these types of questions given my profession.
    Ya know , i was gonna make a smart ass remark about that, and then i remembered how confused you engineer guys get when dealing with simple things

    My son decided to build a 12 x 16 garden shed from a home depot kit (without asking the old man with 40 yrs construction experience) and it came out OK...well at least i don't think it will fall down anytime soon

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    Senior Member NAPOTS's Avatar

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    I have noticed that there not a lot of crossover between my education and the skills of the working professionals that I encounter. Education is not a replacement for experience. I have learned that the best way for something to be successful is to try and get those two things to compliment each other.

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