Diagnosing Boat Battery Drain?

[rainylakefisher]

OK, I'll freely admit electricity isn't my favorite subject, but there are a lot of knowledgeable people on here who can probably help diagnose my problem.

I have an Alumacraft Navigator that loses charge on the starting battery when it sits in the garage. The battery (brand new) runs all electronics and starts the motor. It's wired to the fuse panel in front of the driver's cockpit, and then runs from there to the other components. I have the switches that run lights, bilge, etc... and one of those is wired to the boat radio so that doesn't draw power all the time.

How do I find what is drawing the power? The removalbe navigation lights aren't even hooked up during storage. I disconnect the depth finders. And no other switches are on. Is soemthing on the motore taking power when off? Any thoughts?

[bobbymalone]

i had the same problem and discovered it was the tilt/trim gauge. a switch stops that problem.

is it possible that your motor isn't charging the battery and it just seems like it is loosing power?

is it possible that the battery is taking a dump on you?

[marine_man]

Two easy ways (relatively speaking) to diagnose battery draws are:

1) Take all the connections off the negative side of the battery post. Touch each connection to the post, one at a time.. if there's a spark there's a draw... figure out what's on that circuit and start tracking it down from there.

2) Take all the connections off the negative side of the battery. Connect your test light to the negative post and touch each of the negative connections to the battery. The brighter the test light the higher the draw.

You could do the same as #2 but with a multi meter to understand how many amps you're pulling.

Once you're done with that then the fun begins.. trying to understand where it's coming from. If you find it to be the main fuse panel, you'll need to pull the fuse and use your testlight to see what's drawing power across the fuse and which circuit it is.

What brand motor do you have? It's not a Johnson / Evinrude is it? Older (late 90's) had a very touch rectifier that if the battery connections were crossed even once would fry the rectifier and it would pull the battery down.

marine_man

[marine_man]

i had the same problem and discovered it was the tilt/trim gauge. a switch stops that problem?

This is completely up to you.. but.. there should be no reason that a trim / tilt gauge would do this if it's getting the power for it from the correct spot.

Not sure what you have for a setup, but the trim / tilt switch should be powered when the key is on and not powered when the key is off. The switch works too.. don't get me wrong.

marine_man

[Bigbartguy]

I'm an electrical [PoorWordUsage] but here's my story in case it helps:

the low oil warning alarm quit working on our Merc motor.

It created an open circuit? and drained the battery constantly.

[bobbymalone]

Not sure what you have for a setup, but the trim / tilt switch should be powered when the key is on and not powered when the key is off.

yeah tell me about it. that's the way the boat came wired in '82. It's a hand me down after it sat in my parents pole barn for 15 years. besides the power to the starter and T/T unit there is a pair of wires that run to the fuse box under the console for the lights, bilge pump, aerator, etc. the switch is marked "auxillary" on the console and I just thought it wasn't hooked up to anything. I didn't realize the T/T gauge even required power, I thought it was some sort of mechanical thing. And I thought it was dead for months since it never moved. Then I discovered that switch turns the gauge on and off after I flipped the switch by accident and had a dead battery two weeks later - now I just continually forget to turn it off when coming off the water.

I got a nice reminder to put that on the leaving the lake checklist, when I had the juice to get out but not enough to get back after a week worth of the gauge on in the garage. Fortunately, the trolling motor battery still had enough juice to turn it over and power the nav lights on the way in, otherwise that would have been a mayday type scenario .

[rainylakefisher]

The motor is an 04 Johnson 4-stroke. The battery draw is really small ... like about .5 volts over 8 days. It's on the charger right now as I'm headed to Crane on Thursday morning and I'd like to diagnose it before I leave.

The original boat owner evidently had a similar issue and tried to solve it with a disconnect switch that has since been removed. I need to dig a little deeper ... just wish I understood electricity a little better. A constant frustration for me...

As always, thanks for the help and suggestions.

[efgh]

If you have a radio with didigal push buttons to select stations it requires elec. power to hold the settings of the buttons, this will draw down a battery in time, in my camper it takes about 2 weeks to draw the battery down to less than 1/2 charge. In my boat I have a bulge pump that when turned on checks for water every 4 minutes and then shuts off then on 4 min. later. I killed the bat. once this way.

[yaggie]

Do you have a external GPS antenna? If there is not a switch in the power line to it it can drain the battery after a week or two sitting in a garage trying to find a signal.

[marine_man]

Which circuit causes the draw?

marine_man

[BehindtheHead]

do yourself a favor, put the line disconect back on. when you put it in the garage dis conect it. your battery will always be charged if you have a good battery.

[jeffreyd]

if you use a meter, the most you should read with everything off is .2-.3v anything over that is not good. the easiest way to locate it is if you have your meter on the battery, reading the drain, pull the fuse one at a time for each item and see if it lowers the drain. it could be a couple of things that are causing it. if you locate it via the fuse then you can try and figure out why it is pulling amps out of the battery. Chasing drains can be tough but with patience and a decent meter (digital) you can do a lot of troubleshooting.

I made the note about a digital meter as it is much more sensitive to movement in circuits than the old analog or swing type.

Good luck, let us know what you come up with.