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Author Topic:   Oil in battery compartment

chuck130 posted 06-30-2009 03:22 PM ET (US)
I noticed a small film of colorless odorless oil in my starboard aft battery compartment. I have 2 new AGM sealed batteries which are both showing perfect voltage. The Dauntlass has electric trim tabs and has no internal oil but the power steering on the port aft compartrment which is filled to the exact level.
Could this be mineral oil from the tray to prevent corrosion?
Thanks
pglein posted 06-30-2009 03:46 PM ET (US)
Colorless? Odorless? Is there a chance that it could be water?
I'm not familiar with AGM batteries, but with normal deep cycle batteries, it's not unusual for them to leak a little bit of acid out of the top when charged. This generally looks and feels like slightly oily water (because it is water), but stings your skin and burns holes in clothes.
chuck130 posted 06-30-2009 04:42 PM ET (US)
The AGM battery is sealed and No oil film was on the battery top or sides.
pglein posted 06-30-2009 05:14 PM ET (US)
I've seen plenty of sealed devices leak. And I wouldn't expect that you'd see fluid on top of the battery. Given enough time, liquids always find their way to the bottom of whatever basin they happen to be in.
inlandwhaler posted 07-02-2009 12:59 AM ET (US)
Chuck, I had the exact same experience in the battery compartment of my 20' Campion. The battery is a standard Deka Marine Master and checks out fine and is not leaking. The dealer said they do not put mineral oil or anything else in the tray. Still haven't figured out what is was.
an86carrera posted 07-02-2009 09:00 AM ET (US)
Mold release from the battery case.
Len
pglein posted 07-02-2009 12:54 PM ET (US)
I'm telling you, it's probably just water, either from the battery, or from condensation. If it feels oily, it could just be that it's picking up oils from the plastic in the battery case itself or the box.
And when I talk about a leak, I'm not talking about a leak that would be visible to the naked eye. I'm talking about microscopic fissures in the plastic case of the battery, possibly at the joints where the parts are sealed together. These would be so small that they would only permit very minute amounts of gas to escape when the battery is heated during charging. This gas would then condensate in the closed environment of the battery box, and would eventually find their way to the bottom of the box.
ALL materials are porous to some degree. Even plastic. My father was a plastics engineer for 20 years, designing systems for containing chemicals similar (and in many cases identical) to those found in batteries, only on a MUCH larger scale (think tens of thousands of gallons). They went to great lengths to contain every last drop of the chemicals. But it is a reality of physics; some amount always escapes.
"Sealed" is a relative term.
pglein posted 07-02-2009 12:58 PM ET (US)
Wait a minute, this "film" is in the battery compartment, not the battery box? Is your battery in a plastic box?
Some amount of oily residue will ALWAYS be present in the bilge of a boat, even when it's new. Mold release, fuel vapors, engine oil.... there's always a little. If all your fluid levels are good, then I wouldn't worry about it unless it increases in volume.
chuck130 posted 07-02-2009 04:08 PM ET (US)
It's a small thin layer and it is oily, but all fluid levels are good along with battery voltage.
Thanks for all the info, Chuck

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Author	Topic: Oil in battery compartment
chuck130	posted 06-30-2009 03:22 PM ET (US) I noticed a small film of colorless odorless oil in my starboard aft battery compartment. I have 2 new AGM sealed batteries which are both showing perfect voltage. The Dauntlass has electric trim tabs and has no internal oil but the power steering on the port aft compartrment which is filled to the exact level. Could this be mineral oil from the tray to prevent corrosion? Thanks
pglein	posted 06-30-2009 03:46 PM ET (US) Colorless? Odorless? Is there a chance that it could be water? I'm not familiar with AGM batteries, but with normal deep cycle batteries, it's not unusual for them to leak a little bit of acid out of the top when charged. This generally looks and feels like slightly oily water (because it is water), but stings your skin and burns holes in clothes.
chuck130	posted 06-30-2009 04:42 PM ET (US) The AGM battery is sealed and No oil film was on the battery top or sides.
pglein	posted 06-30-2009 05:14 PM ET (US) I've seen plenty of sealed devices leak. And I wouldn't expect that you'd see fluid on top of the battery. Given enough time, liquids always find their way to the bottom of whatever basin they happen to be in.
inlandwhaler	posted 07-02-2009 12:59 AM ET (US) Chuck, I had the exact same experience in the battery compartment of my 20' Campion. The battery is a standard Deka Marine Master and checks out fine and is not leaking. The dealer said they do not put mineral oil or anything else in the tray. Still haven't figured out what is was.
an86carrera	posted 07-02-2009 09:00 AM ET (US) Mold release from the battery case. Len
pglein	posted 07-02-2009 12:54 PM ET (US) I'm telling you, it's probably just water, either from the battery, or from condensation. If it feels oily, it could just be that it's picking up oils from the plastic in the battery case itself or the box. And when I talk about a leak, I'm not talking about a leak that would be visible to the naked eye. I'm talking about microscopic fissures in the plastic case of the battery, possibly at the joints where the parts are sealed together. These would be so small that they would only permit very minute amounts of gas to escape when the battery is heated during charging. This gas would then condensate in the closed environment of the battery box, and would eventually find their way to the bottom of the box. ALL materials are porous to some degree. Even plastic. My father was a plastics engineer for 20 years, designing systems for containing chemicals similar (and in many cases identical) to those found in batteries, only on a MUCH larger scale (think tens of thousands of gallons). They went to great lengths to contain every last drop of the chemicals. But it is a reality of physics; some amount always escapes. "Sealed" is a relative term.
pglein	posted 07-02-2009 12:58 PM ET (US) Wait a minute, this "film" is in the battery compartment, not the battery box? Is your battery in a plastic box? Some amount of oily residue will ALWAYS be present in the bilge of a boat, even when it's new. Mold release, fuel vapors, engine oil.... there's always a little. If all your fluid levels are good, then I wouldn't worry about it unless it increases in volume.
chuck130	posted 07-02-2009 04:08 PM ET (US) It's a small thin layer and it is oily, but all fluid levels are good along with battery voltage. Thanks for all the info, Chuck