Battery drains down over a week's time at mooring

[tiquelover]

I need some advice as to how to track down what is causing this problem. Normally I leave the main battery switch on my #2 house battery, with only the master dc breaker on along with the bilge pump breaker. Rarely if ever does the bilge pump run, most when I run it to check if it needs to pump. My amp meter pegs out showing full draw of amps when I check usage. The boat is 15 years old but with a new electrical panel, newish batteries. The boat was rewired prior to my purchase and thus am unsure what or how it was wired. when I check the distribution panel for voltage even while the master battery switch is off, I find juice.
Any advice would be very welcome.
Wayne on Wine Down

[AnchorageGuy]

Wayne, Unfortunately wiring problems can be almost anything and some can be simple to find and others take weeks. I suggest you start disconnecting things, starting with the wire from your battery switch to the panel. See if there is still power going to the panel. If so something is wired directly from the battery to the panel. Disconnect wire by wire until the power is gone and that is the problem. Check the cables on your battery switch to be sure they are not connected wrong. If the amp meter pegs out there is something wired wrong and it could be the amp meter. And all of this is just the start. The problem could be anywhere on the boat and only by starting from the batteries and moving through the system will you determine what and where.

[Sandero]

Oy, You have some load on and you don't know it. So how about putting a meter on and disconnect every circuit one by one to see if you can find the guilty culprit. You might have a mis wiring someplace leaking 12v to ground.

Wire your bilge pump directly to the battery and turn all battery switches to off for a week and then see what gives.

[SilentOption]

Originally Posted by tiquelover

I need some advice as to how to track down what is causing this problem. Normally I leave the main battery switch on my #2 house battery, with only the master dc breaker on along with the bilge pump breaker. Rarely if ever does the bilge pump run, most when I run it to check if it needs to pump. My amp meter pegs out showing full draw of amps when I check usage. The boat is 15 years old but with a new electrical panel, newish batteries. The boat was rewired prior to my purchase and thus am unsure what or how it was wired. when I check the distribution panel for voltage even while the master battery switch is off, I find juice.
Any advice would be very welcome.
Wayne on Wine Down

Just a few more details might help.

Explain what you mean by Amp meter pegs out when you check usage.
Explain how you are checking usage? And usage of what? Batteries, pump?
Do you mean it pegs when you turn on the bilge pump?
What does the amp meter show when the bilge pump is in auto but not pumping?
Has the problem existed since you bought the boat?

Take a digital picture of the front and back of the panel and point out where you find power.

I agree with Chuck that problems like this can be hard to track down but if you have one battery switch and one panel it might not be all that tough.

You can start by inspecting the back of the panel and make sure every terminal lug straight and not touching something it shouldn't be. Check every positive and every ground.

Also look at places where wires go through bulkheads. Sometimes wire will chafe if it was properly protected.

If you put up more details someone may come up with an answer in short order.

[Maine Sail]

I have seen a lot of questions over the years about parasitic battery loads (current draw on your battery even when everything appears to be turned off) and wanted to post a quickie on how I generally isolate and find them.

In order to trace ghost or parasitic loads you'll need the proper tool. You'll want a multi-meter that will read DC amps / millivolts out to the thousandths or at a minimum the hundredths.

These meters can be had very cheaply these days and while the cheapies might not be the most accurate you are only looking to eliminate or make the current draw disappear on the meters screen through a process of elimination.

If you find you have a parasitic load you can easily track it down by disconnecting load wires from the back of the panel , one by one, while monitoring the meter, or anywhere a load pulls off the circuit down stream/current of the meter.

To test for this you simply insert the meter between the positive post of the battery and the positive battery cable. Please only do this with everything turned OFF!!! I can't stress this enough. ALL loads must be turned off including the battery switch before inserting your multimeter.

The fuses in multimeters, for reading milliamp DC current, are usually a 2 amp fuse MAX. Do not blow this fuse or the meter will no longer work. Fixing it will most likely require you to disassemble the meter to change the circuit board mounted fuse.

Once you've connected the positive lead from the multi-meter to the positive battery post, and the negative wire from the meter to the battery cable, set your meter to read milliamps and plug your cables into the appropriate sockets on the meter.

Once you flip on the meter it will either read .000, meaning you have no parasitic load, or a current flow such as the one pictured below.

Please note that I set this up in my garage and used a Sensibulb as my current draw hence the teeny tiny wire I labeled "battery cable". Your battery cable would be considerably larger..

Of course, like anything, there are more ways than this to achieve the same outcome but I find this to be the easiest and one of the fastest. A clamp meter that does DC amps/millivolt would actually be easier. I chose not to use my clamp meter for this because I know how "penny wise" sailors are and I also realize that suggesting the use of an "expensive" DC clamp meter would get me laughed off the board..

[Stillraining]

Originally Posted by Acoustic

I chose not to use my clamp meter for this because I know how "penny wise" sailors are and I also realize that suggesting the use of an "expensive" DC clamp meter would get me laughed off the board..

Ha Ha Ha..you silly Goose you MainSail

[over40pirate]

The easiest way to check for a draw when everything is shut off, is to disconnect your + battery cable, and connect a small 12 volt light bulb between the bat. post and cable. If there is a draw, even in the milliamp range, the bulb will light.

Also, be sure the top case of the battery is clean. Believe it or not, a dirty battery top can conduct juice. In a previous live, I was an auto mechanic and many times, cleaning the battery cured a battery that would self discharge while sitting.
On a dirty battery, hook a voltmeter to the negative post, and touch the other voltmeter lead to areas on the top of the battery. Got voltage? Hmmmmmm.

[cabo_sailor]

Would it not be possible that his battery is shot? Seems to me a load test would be in order.

[henkmeuzelaar]

This is one of the many DC current problems where the advantages of using an "expensive" DC clamp meter are so huge that it is almost criminally negligent (with regard to the wise use of your own time) not to use one here, even if you have to borrow it from someone else in the marina or harbor.
As long as the DC clamp meter that you use is able to measure as little as 10-20 mA DC it will only take you a few minutes to see if any significant parasitic loads exist (or simply overlooked current draws; e.g. by a gas sensor), without having to disconnect a single wire.
If you don't find a measurable current draw after you have shut all known devices off and your battery still is empty within a week then you can conclude that your battery is shot. If the current draw is too small to be measured, let's say up to 10 mA, then the maximum Amp hour loss per week is less than 2 and any marine-sized battery should be able to deliver that easily.
The one big trap you could still fall into when using a sensitive DC current meter is that the current draw(s) that empty your battery might be intermittent and therefore not necessarily detected when you take your measurements. Notorious examples are, of course, bilge pumps (especially since they often are wired in such a way as to bypass your panel meters), refrigerators, instrument lights that only come on at night and any type of electrical short (e.g. two wires touching somewhere) that depends on the boat moving a bit. If all other explanations fail, this could be a reason to leave the clamp meter on and watch it for several hours, even if it means having to insert a new battery into the meter.

Have fun!

Flying Dutchman

[Blue Stocking]

Is it possible that you have a ground wire picking up induced current in a harness somewhere. Got a call once to a dive boat, that some mornings the crew would go on board and find the 6-71 GM running. Couldn't figure out why! Then one morning while the crew were getting on board, the very large submersible bilge pump kicked in, and the engine started. Turns out the feed to the pump was in the harness containing the ignition start wire to the solenoid. Induced current pulled in the solenoid, and the GM came to life.

[Stillraining]

Originally Posted by Blue Stocking

Is it possible that you have a ground wire picking up induced current in a harness somewhere. Got a call once to a dive boat, that some mornings the crew would go on board and find the 6-71 GM running. Couldn't figure out why! Then one morning while the crew were getting on board, the very large submersible bilge pump kicked in, and the engine started. Turns out the feed to the pump was in the harness containing the ignition start wire to the solenoid. Induced current pulled in the solenoid, and the GM came to life.

Thats the freakiest and coolest thing "boat" I have ever heard..
Auto start battrie charge indicator..that boat aint never sinking due to low battery juice from the bilge pump...Thats absolutely ingenious..he should patent it

[Cadence]

I'd look for a leakage path around terminals. any kind of sulfates on adjacent terminals. For what it is worth. If it takes a week it's a tickle, hard to measure. Isolation by disconnecting would work, how many circuits and weeks do you have. I think for the health of your batterys. I'd go backwards. disconnect everything and add the circuits back one at a time until you find the leaker.

I don't think your going to find an insulation failure in the wires. It's going to be at some terminals. The suggestion of checking for wear going through bulkheads makes sense again I'd look for some form of corrosion. A boat is one big battery in salt water.