Grady 208 Port battery issue?

Mark DV

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Need some advice. I can't figure out a battery issue. My port battery always reads 12.4 volts after sitting for a couple days and doesn't go down less than that.. after charging it reads 13 volts. Seems like something is draining it? This battery died last summer and I replaced. Starboard battery is always 13 volts. I have a guest battery disconnect. I always disconnect when not in use. I have eliminated bilge pump and stereo memory lead. What else could be the issue?
 

seasick

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charge the battery again, disconnect all ground connections, measure the voltage and write it down. Now let it sit disconnected for a few days and measure again. Let us know what it reads.
Also check your voltmeter, do not rely on the reading on the gauges or any devices like GPS. Use a decent digital voltmeter. I am skeptical that the standing voltage after charging is 13 volts.
 
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Hookup1

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Batteries should read 12.8 volts off the charger. May show a little higher just off the charger (surface charge). How old are the batteries? I use 5 years +/- for battery life. That one battery may have a cell on its way out. Seasick is right - use a meter not gauges - and make sure meter reads correctly.
 
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Mark DV

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Battery was installed new in September 2020. The older port battery went dead. Which is why I am skeptical. I am using a voltmeter. I will charge battery, disconnect and check voltage. Will report back.
 

Mark DV

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Ok. So after day one after battery charged and everything disconnected voltage was 12.6. I just checked it again and voltage is 12.5. Voltage was 12.8 right off charger.
Batteries should read 12.8 volts off the charger. May show a little higher just off the charger (surface charge). How old are the batteries? I use 5 years +/- for battery life. That one battery may have a cell on its way out. Seasick is right - use a meter not gauges - and make sure meter reads correctly.
Ok. So after day one after battery charged and everything disconnected voltage was 12.7. I just checked it again(day 2) and voltage is 12.5. Voltage was 12.9 right off charger.
 

wspitler

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A battery can show good voltage and still be weak. Check it with 100 amp load meter (cheap at Harbor freight or any auto parts store can check it for you.) See if it maintains voltage. I just had a battery that showed 12.7 V after a day of sitting but when the load was applied voltage went essentially to zero and returned to above 12 V after the load was removed.
 

DennisG01

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Ok. So after day one after battery charged and everything disconnected voltage was 12.6. I just checked it again and voltage is 12.5. Voltage was 12.8 right off charger.

Ok. So after day one after battery charged and everything disconnected voltage was 12.7. I just checked it again(day 2) and voltage is 12.5. Voltage was 12.9 right off charger.
Well, you've got two different sets of numbers there that you're talking about - weird.

But, are you saying that after just two days of sitting it's already down to 12.5? And it's only 6 months old? Not good.

Charge it up and go get it load tested.
 

seasick

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Don't recharge right now. Take the battery as is to Auto Zone or similar store and have them load test it.
 

Mark DV

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Well, you've got two different sets of numbers there that you're talking about - weird.

But, are you saying that after just two days of sitting it's already down to 12.5? And it's only 6 months old? Not good.

Charge it up and go get it load tested.
Sorry. Typo. The second set is correct. I had to go back and look at my notes. I think this battery us garbage.
 

PointedRose

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Sorry. Typo. The second set is correct. I had to go back and look at my notes. I think this battery us garbage.
Can you swap your batteries to make sure it’s the battery that’s the issue and not something else? If you switch the sides, both charged, you’d expect the same result regardless of which side it’s on, and if the same battery still drains, it might be a couple of boat bucks to replace that and hopefully your issue is solved.
 

Hookup1

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Clean battery tops - dirt, carbon and moisture will discharge them. Check water levels and fill with distilled water.Take them to a store had have them load tested.

Your batteries seem ok but one may be on its way out. How old is the other battery?