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Mysterious Power Drain

Old 04-11-2010, 09:19 PM
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Default Mysterious Power Drain

I'm now on my 3rd battery now since last summer.

I finally pulled out my multi-meter and measured a 200mA current draw with everything turned OFF!!

So, something on my boat has changed late last summer and that's why the last 3 times I went to turn my boat on this season, I've had to replace the battery.

I went through the fuse block under my dash and measured the current after pulling each fuse, but found nothing. Where else should I look for this mysterious current draw?
Old 04-11-2010, 09:44 PM
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Is your bilge pump/float switch hard wired? In mine its the only thing that runs when the battery switch is off.
Old 04-12-2010, 04:05 AM
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Could be things like LP gas sniffer, CO detector, fire system monitors, digital battery monitors, alternator regulators. These things can be wired before the battery disconnect switch in what is known as 24 hour circuits. 200ma isn't much but over a period of weeks/months, can severely drain a battery or battery bank. That's about 5AH a day so with just one battery it could drain it pretty quick. You should never let your batteries fall below 12.4 when not in use as they will start to sulfate and that ruins batteries.

Eric
Old 04-12-2010, 05:21 AM
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Why not put in a switch that can be turned off. Keep the bilge pump hard wired.
Old 04-12-2010, 06:26 AM
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Originally Posted by fairbank56 View Post
Could be things like LP gas sniffer, CO detector, fire system monitors, digital battery monitors, alternator regulators. These things can be wired before the battery disconnect switch in what is known as 24 hour circuits...........
Exactly. You didn't say anything about the boat, but boats with sleeping areas are supposed to have carbon monoxide detectors (200 ma is about right for one) and they are usually wired to bypass any battery switch in case someone is on the boat with the battery switch turned "off".

A CO detector should have an indicator light on it so turn the battery switch off and see if the light stays on.

Many stereo systems have a memory circuit that is powered all the time but they don't draw anywhere near that amount of current.
Old 04-12-2010, 08:26 AM
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NMEA 2000 networks oftentimes stay powered up (depending on how they are wired) even though you've got all your networked electronics turned off
Old 04-12-2010, 08:30 AM
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I got it figured out. I've got a radio installed in the glove box. Apparently, if the radio is on when the battery is pulled, it'll automatically turn back on when the battery is replaced.

Too bad I had to go through 3 batteries to learn this lesson!

Thanks everyone for your suggestions. It was your suggestions that lead me to looking at things that are wired directly to the battery, like my radio.
Old 04-12-2010, 09:40 AM
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Originally Posted by ignisuti View Post
I got it figured out. I've got a radio installed in the glove box. Apparently, if the radio is on when the battery is pulled, it'll automatically turn back on when the battery is replaced.

Too bad I had to go through 3 batteries to learn this lesson!

Thanks everyone for your suggestions. It was your suggestions that lead me to looking at things that are wired directly to the battery, like my radio.
How did the radio come to be wired directly to the battery?

It should really be after the battery switch. Bettery yet, connected to the accessory position of the ignition switch (if you have one).
Old 04-12-2010, 09:53 AM
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Must have been something a previous owner has done. I'd like to wire it up to the accessory switch, but I'd have to run a wire all the way around my boat. And, I guess it'd have to be a heavier gauge wire as well.

So, might just leave it the way it is and watch for it in the future.

P.S. My boat doesn't have a main battery switch.
Old 04-12-2010, 01:05 PM
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How about your GPS module? If it is not switched, they are notorious for killing batteries in just a week or so.

Edd

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