View Full Version : Battery running down

04-02-2008, 11:46 AM
One of my accessories is pulling current from my battery even when the key isn't in the ignition. I haven't been able to figure out which one it is so I've resorted to pulling the battery terminals off when I'm not running the boat.

This is getting a bit tedious so I'm planning on adding another battery and then inserting the relay that Diesel talks about in the Dual Battery thread. My question is this, when the key is not in the ignition does the relay prevent both of the batteries from running down, or as I'm guessing, just one of them? I'm thinking having a battery that constantly gets run down is going to need to be replaced soon - so I should probably double my efforts to find the current leak regardless of how I set things up.

Thanks for any help!

04-02-2008, 12:11 PM
If you don't find the problem, I would just put a switch in....save both the batteries. Cheap, and easy to do.

04-02-2008, 01:07 PM
do you have some sort of location (such as a fuse panel or circuit breaker box) that all accessories go to? if so, get a multimeter and check voltage of each location with all the switches off. Then turn the switch on and see if the voltage changes. or you can remove each switch or assessory button and check the current there. don't put a bandaid on the problem by adding another battery with switch, find where the current draw is coming from!

04-02-2008, 05:28 PM
I'll try to get out there this weekend w/ my voltmeter again and see if I can find anything...thanks for the responses.

04-02-2008, 09:34 PM
If you do end up putting a switch on the batteries, make sure that you still have power going to the bilge pumps. In fact you might want to check the bilge pumps first to make sure they're not always on due to debris in the float switch (depending on style).

04-02-2008, 10:34 PM
You don't need a voltmeter, you need an ammeter. Remove the negative battery terminal, connect the ammeter in series and read the current draw. I would bet that it's in the 300-350mA range. If this is close to the draw, go to ht ealternator and remove the purple wire and it'll probably go to about 15mA. If this is the case, your bridge rectifier is shot and will need to be replaced but since it means that the distributor needs to be disassembled, you may as well buy a rebuilt one. If you plan to add a bunch of accessories, tell them what you plan to add and how much current they will draw, so they can get you into a 95A (or higher) version. If you go much higher than the stock alternator, your charging lead will have to be replaced with a larger one in order to handle the current at full load.

If the current draw is higher than 350mA, check your storage area light.

04-03-2008, 12:20 AM
What would be a "normal" current draw? Granted, it all depend on your accessories. What accessories typically draw current when the boat is "off?" Possibly a clock, stereo head unit, PerfectPass, ECU (engine control unit), etc.

04-03-2008, 12:45 AM
15-30mA is about normal. any higher means some device is on, leaky or there's some kind of short. If it's much less, start pulling fuses, one at a time to isolate the draw. The memory circuit of a head unit draws about 15mA. The ECM may draw a similar amount and there's no need for a clock that's separate from the head unit. If the head unit's red lead is always hot , that will kill a battery even if the head unit is off although obviously not as fast as if it was on.

04-03-2008, 01:33 AM
JimN, good information. I was just trying to ask questions that might help him in his diagnosis.

I had to replace a stereo head unit in our old, non-MC boat, because the manu. used a car stereo head unit. I replaced it with a fairly inexpensive one that guaranteed that it would not drain any current from the battery when it was off. Can't stereo head units use NVRAM to maintain settings and such?

Also, our 2005 X-2 has a clock in the dash as a part of the multifunction display. So, it has to be sucking up some current at all times.

I hope that he gets it figured out. Something else to consider is that a battery on its last legs will charge, but dissipate quicker than a healthy battery.

04-03-2008, 06:36 AM
If the current draw is higher than 350mA, check your storage area light.
:D ;) :D !!!!

04-03-2008, 09:45 AM
"Can't stereo head units use NVRAM to maintain settings and such?"

Can they? Sure. Will they put it in and raise the price? Not liklely.