Mystery Electrical Power Drain

[Whole in the Water]

My 2 brand new batteries are losing their charge slowly over time (i.e. 2-3 weeks) after non use. Just like the previous ones.

This is still happening after I have disconnected my bilge float switch from the battery and battery switch is turned off. My alternator on my main engine and kicker work great when their running. I also have an isolation switch on my depth sounder that completely turns off the power supply to the unit and the black box is turned off. All electronics are taken off the boat when not in use.

When I check for voltage from my +/- distribution posts that are above the battery switch I get a 0.oo1 volt or 1.3 milli watt volts reading when the battery switch is turned to off. I am thinking this should read zero.

Any ideas what is causing this power draw and how to fix it?

 

[Troller]

I get a 0.oo1 volt or 1.3 milli watt volts reading when the battery switch is turned to off

Never heard of a milli watt volt but the .001 volt reading is probably the meter not zeroed. What reading do you get with the meter leads shorted together?

A better test would be to disconnect a battery lead and put the meter leads between the battery and the battery lead with the battery switch off. The meter should be set to read amps or milliamps. Do this with both batteries. This will tell you if something is draining the battery.

 

[1marko]

Stray voltage can be lost in may ways...most times simply through the shear complexity of the entire system . One sure fire way
to avoid a flat electrical storage bank is to isolate with a switch as most know and have. Aside from this moving forward exists
a vast network or controls, cables and connections ....All of which should be suspect and looked at to either be cleaned and reconnected
periodically...

 

[SteelyDan]

Disconnect a negative battery cable and connect a test light from the disconnected cable to the negative post. If it lights up you have a short. Next go through every fuse on your boat and pull them 1 by 1 watching the test light. When it goes out you have located the source. Now you owe me a beer because I normally dont tell people this **** lol

 

[Rain City]

Set it on fire. Start over.

 

[Sotally Tober]

Set it on fire. Start over.

LOL! I'll try to remember that when I have a problem

 

[profisher]

My elderly neighbor had a problem with their RV which always ended up with dead batteries when they went to start it up in the winter just to move the oil in the engine and work the transmission in and out of gear to move fluid in there as well. I knew that the car show guys often use a cheap isolation switch that mounts right on the positive battery post. It is a cheap $10.00 part which works by turning out a knob that breaks battery contact. When you want to use the battery simply turn it a turn or two until it seats and won't turn anymore and you are connected again. It worked great for them...never had the problem ever again. I bought that one for them at Battery Direct (Canadian Energy)

 

[Fox]

Disconnect a negative battery cable and connect a test light from the disconnected cable to the negative post. If it lights up you have a short. Next go through every fuse on your boat and pull them 1 by 1 watching the test light. When it goes out you have located the source. Now you owe me a beer because I normally dont tell people this **** lol

Easiest way to find the offending circuit. Or if it’s not enough juice to power the light, use a multimeter instead of test light.

 

[fish brain]

Like SteelyDan said, only I would use a multimeter like Fox does

 

[profisher]

I agree to fix the problem but with after that this cheap switch prevents an early morning surprise of a dead battery at the boat ramp.

 

[ericl]

Use the method posted by steelydan. To measure current or wattage, you need to break the electrical circuit as he mentions. You can only measure voltage or resistance by just putting the meter probes between ground and the measurement point.

It is highly unwise to disable the auto bilge pump operation.
You need a proper battery charger in your system; all batteries will self discharge over time; but 2-3 weeks is abnormal.
You need to measure the battery voltage after using the boat to make sure the batteries are getting a full charge; you could have a faulty voltage regulator in your charging system. The batteries should measure at least 13.8 volts.

An explanation on how your 2 batteries are being used together would be helpful.

 

[profisher]

If your main engine cranks over slower than normal after a long day of fishing then as Eric says above I would suspect you are not charging. I had a loose connection on my kicker that meant it wasn't charging. The only charging I was getting was from the main on the run out and back. After fishing my main turned over on the starter noticeably slower which tipped me to there being a problem.

 

[Kristo]

The batteries on my previous boat would discharge slowly and had to be charged regularly...the problem was the main engine was not charging the batteries because the wires on the stator were reversed. Engine was OX66 225.

 

[bigdogeh]

I had a weird voltage drainage problem awhile back. Did a lot of tests and found that my rule float switch was draining a small amount of amps even though the switch wasn't in the float position. The switch was in a small well that had filled with salt water at one time and the water had evaporated. some of the water must have gotten into the switch somehow and the dried salt crystals were actually conducting electricity. I wouldn't have found the problem without having an audio alarm installed on my bilge pump switches that goes off when the switches activate. The alarm would go off on this one even in the off state or when the float wasn't floating or raised. I could measure a small amount of voltage draining through the switch (using a voltmeter) even when it wasn't triggered. Changed the float switch and all was good again. The audio alarm was very slight since it was a really small amount of voltage was draining but it was just enough to hear. Took me awhile to find the problem as I was thinking I had a wiring issue somewhere and never expected the switch itself to be faulty...

 

[bpsuls]

The test suggested by troller is the best one. Use a multimeter, set it to 10amps in case it's a significant draw, which it sounds like. You will find that there is always some parasitic current draw from electronics who require power to keep time, etc. Even when they are off. This should be in the order of 100mA or less per device. Check all the fuses one at a time. I would pull them all and start putting them in one at a time and watch the meter. If you see anything in the 1 amp+ range, that is likely your problem.

Although most marine electronics are very robust, in general I never use test lights to check circuits with electronics on them. Too easy to back feed power into sensitive electronics that don't do well with that. Learned that doing electronic diagnostics on cars a long time ago. Test lights are for testing trailer lights and the like only in my option. Use a multimeter for everything else. Ask me about my diagnosis of a faulty trim tab a couple years ago. Could smell the burned pcb material from the fish deck. Should have used the multimeter!

On the issue of your engine's alternator health as a culprit, if your volt meter shows 14v within 30 seconds of starting the engine and shows it at idle, you're probably fine.

 

[Fixit]

good advise on using a multimeter to check for current draw.

on another note, your batteries should be 99% isolated with the battery switch, (boat goes down with a dead battery from the bilge pump running)
so even if you have a (insert electric device here__________ ) drawing 300mA, the battery switch should stop your dead battery problem.

like others had asked for, please describe your dual battery set up.

my setup is a house and a start battery. Charging/discharging is supervised by a blue seas ACR.
house takes care of downriggers, plotter, prawn puller, deck lights, stereo, etc etc etc.
start battery is only connected to the main and kicker (and a bilge pump switch)

with this setup i could kill the house battery, but still flash up either engine to get home

 

[Wild Bill]

Same test as above however set the vom to dc volts and put between battery post and disconnected battery terminal, if the reading is anything less than your battery voltage you don't have a draw. If the voltages are the same set your vom to amps and check.
I have seen alternator voltage regulators stay energized however that would typically be in the area of 3 to 5 amps and that would kill the battery in a day or so.