Classic AquaSport

Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Electrical => Topic started by: bluedolphin on January 21, 2007, 01:46:38 PM

Title: Low Battery Voltage
Post by: bluedolphin on January 21, 2007, 01:46:38 PM

1972 22' Aquasport CC with a `82 Mercury V6 200 hp. After charging on land, the house battery reads 13.2v (reading through the fisfinder). After a day, the voltage is down to 12.5v. After another day, it reads 12.4v. I don't know if the other (engine) battery reads the same as the house battery. What's causing this drop in voltage?  Almost dead battery? Something draining the battery? HELP!!!

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Post by: JimCt on January 21, 2007, 01:53:35 PM

You may have a bad diode in the charging circuit or a leak to ground somewhere.

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Post by: jdupree on January 21, 2007, 02:33:48 PM

I don't know if the rectifier is linked into the charging system on a 200 Mercury, but that might fix the tach and the charging problem.  If you will go to themarinedoctor.com it will show you how to check the rectifier to make sure that it is working.

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Post by: JimCt on January 21, 2007, 02:40:46 PM

Have you added anything electrical recently?  If you have, you might want to try disconnecting it to see if that improves the situation.

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Post by: warthog5 on January 21, 2007, 04:07:14 PM

Start with probing the batteries with a VOM meter to check their voltage. 12.6V is what your looking for for full charge.

Run the motor on the muff's. Bring the RPM up to 2000RPM. Now prob the batteries again.

You should see aprox 14.2V at 2000RPM.  This will check the charging system.

If that's OK it's time to bring the batteries to full charge and have them load tested.

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Post by: John Jones on January 21, 2007, 07:37:21 PM

Quote from: "JimCt"

you might want to try disconnecting it to see if that improves the situation.

Yep.  Something, either internal or external to the battery is draining it.   With the charger off, it should read about 12.6 like wart said.  It should stay above 12V for weeks with no load.

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Post by: bluedolphin on January 21, 2007, 10:49:32 PM

Thanks, all. Actually, even with the engine running, the voltage reading is showing 12.3 or 12.4 (again, thru the fishfinder). So, like someone suggested, maybe the "rectifier" is not working. I have not had any problem starting the engine, though. Just worried about the low voltage.

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Post by: JimCt on January 22, 2007, 08:07:02 AM

How old is the battery?

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Post by: warthog5 on January 22, 2007, 09:25:00 AM

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again, thru the fishfinder.

That may be telling you correct, then again it may not. That's why you use a VOM right to the battery terminal's to eliminate this as maybe good maybe not good thru the fishfinder.

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Post by: bluedolphin on January 22, 2007, 01:04:55 PM

Batteries are 2006 (label on the batteries). I will use a VOM to check voltage straight from the batteries. Thanks.

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Post by: John Jones on January 22, 2007, 06:38:38 PM

Quote from: "warthog5"

Quote

again, thru the fishfinder.

That may be telling you correct, then again it may not. That's why you use a VOM right to the battery terminal's to eliminate this as maybe good maybe not good thru the fishfinder.

Yep.

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Post by: ddd222 on January 28, 2007, 07:26:36 PM

shot in the dark but has anyone suggested a live wire somewhere, maybe in bilge or livewell area?

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Post by: JimCt on January 28, 2007, 09:06:30 PM

ddd's got a good point.  A small crack in wire insulation + saltwater can do it.