Chasing down electrical leakage

[LongLine]

How do you chase down a short in boat equipment & circuits?

My fishfinder (Raymarine DS500x) connects to the battery with 2 wires. (red-pos, blk-neg) With the unit off, I undid one wire nut & put my cheap volt/ohm meter across the two wires and read 12.6 v. Reconnected those 2 wires then undid the fuse in the other line. With a probe in each end of the fuse holder, it read -12.6v. (unit still turned off)

Need a sanity check here please. The fishfinder is drawing power while it?s turned off or my electrical theory is all wrong.

The problem I?m having is a battery (new last year & charged over the winter) that goes dead with the boat sitting on my trailer for a week.

Thanx for any thoughts.

Tom B.
(LongLine)

 

[dozerII]

Re: Chasing down electrical leakage

I am having the same problem in my 5th wheel. The stereo killed the batteries over the winter, and the dead batteries froze and split leaking acid everywhere. The only way I found this out was when I was installing the new batteries when I was hooking up the ground I saw a small spark when I touched the cable to the post. I hooked it up and went in the trailer to see what could be on. The stereo was off but it has an led display for the clock, I pulled the fuse and then disconnected the battery and checked for a spark, nothing, so I installed a switch in the panel next to the stereo to positivly kill it. I think your fish finder has memory that is drawing like my stereo. Try just dragging the ground from it across the - post to see if it sparks.
Glen

 

[trendsetter240]

Re: Chasing down electrical leakage

How do you chase down a short in boat equipment & circuits?

My fishfinder (Raymarine DS500x) connects to the battery with 2 wires. (red-pos, blk-neg) With the unit off, I undid one wire nut & put my cheap volt/ohm meter across the two wires and read 12.6 v. Reconnected those 2 wires then undid the fuse in the other line. With a probe in each end of the fuse holder, it read -12.6v. (unit still turned off)

Need a sanity check here please. The fishfinder is drawing power while it?s turned off or my electrical theory is all wrong.

The problem I?m having is a battery (new last year & charged over the winter) that goes dead with the boat sitting on my trailer for a week.

Thanx for any thoughts.

Tom B.
(LongLine)

Your tests only showed that voltage was present. You will get the same reading anywhere in a negative ground system as long as you touch a positive and negative source with your meter.

Just because there is voltage present it does not mean that anything is drawing a current. You need to measure Amperes to determine if the unit is drawing any power at all. Just be careful as most small meters can only handle up to 10amps and only for brief periods of time.

NEVER connect a positve and negative line in the boat when measuring current. Measurements should be on the positive line only.

 

[wire2]

Re: Chasing down electrical leakage

Opening the positive led to put a voltmeter in between, places the fish finder and a high input resistance meter in series.

Theoretically, if the finder is turned off, the meter *should* show 0 volts. But typically, the off/on switch is not hard wired, but is one of several inputs to a programmed chip, which will draw a few microamps of current on standby.

Is the power button "push on/push off" with no audible click? That's enough to allow the meter to show 12v.

Your finder may be drawing more than that due to a defect, so as suggested above, use the meter to read current across the 2 positive connections you opened to read voltage.

You can also use a 12 volt lamp with 2 wire leads to find an unwanted load. Undo the pos cable from the battery, connect 1 lamp wire to the post, the other to the cable clamp. If a low wattage lamp doesn't light, there's virtually no current being drawn by the boat (or car) wiring.

 

[Silvertip]

Re: Chasing down electrical leakage

The camper and a boat battery can be totally discharged over the winter because the radio has a "station memory" that requires a small amount of current to prevent loss of station presets. Although that current draw is small, it will kill a battery(ies) over several months of storage. As for the boat issue, if you have a short, a fuse would be blown. Yes, some locators draw a small current even when off. So does the radio. You need an on-board charger that is plugged into AC power at the dock or at home. This will keep the batteries topped off. Or, install a master disconnect switch at the battery. You will need to reset the radio each time but that's sure less of an issue than a dead battery.

 

[boat127]

Re: Chasing down electrical leakage

you shouldn't leave batteries hooked up over winter

 

[DianneB]

Re: Chasing down electrical leakage

All modern electronic equipment will draw a small amount of current constantly, like up to a couple of milliamperes (0.001 A) but "dead with the boat sitting on my trailer for a week" means there is more load than just a few milliamperes.

The lamp test mentioned above will help you track down the culprit.

 

[Silvertip]

Re: Chasing down electrical leakage

And a short would blow fuses. There is no "partial" short. A circuit is either shorted or it's not. To find the culprit, pull one fuse at a time while doing a parasitic current draw test. Any meter with a 10 amp draw capacity will work. I would be looking for courtesy lights staying on, dash switch indicator lights staying on, ignition left on if you have an I/O or you may have a battery going bad. Outboards don't take much power to start so a marginal battery may seem ok but tend to self discharge over a week. The first step would be to have the battery load tested. There are 168 hours in a week so as little as a 1 amp draw would kill a good battery in a very short time and a weak one, or one with marinal capacity in even less time..