Author Topic: Why is the top of my Batteries wet ?  (Read 14738 times)

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Offline WooferHound

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Why is the top of my Batteries wet ?
« on: March 21, 2012, 08:17:42 am »
My last battery was a 12v 8D truck battery. I noticed that the top of the battery tended to stay wet or very moist.
Now I have two 6v golf cart batteries. While looking over the system yesterday I noticed that the top of those batteries was wet.
I looked into all these batteries when they were full charged and dumping and they were slowly bubbling, maybe a bubble every couple of seconds. It doesn't seem like this slow bubbling would cause moisture on top of the battery.
I have 2 stages of dumping in my charge controller.
A 3 amp dump comes on at 14.6 volts and
a 6 amp dump comes on at 14.7 volts
Sometimes when I'm not home and using the power, the battery voltage will get up to the 14.7 volt stage at 11:AM in the morning and remain there all day, maybe that is too high.
I'm just afraid that the acid may be getting out of the battery. What would cause the top of the batteries to get wet like that ?

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Offline birdhouse

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Re: Why is the top of my Batteries wet ?
« Reply #1 on: March 21, 2012, 10:13:29 am »
woof-
from what i've witnessed, the water from a battery will evaporate, while the acid will not.  so if a tiny bit of acid gets out here and there and maybe it's a cumulative effect, and they start looking wet? 

an easy test would be to dab a bit of baking soda on the wet spot, if it bubbles a lot, you know it's acid. 

your 14.7 does sound a bit high to me...  do you have to add water often? 

is the wattage of your solar pretty large compared to the AH of your batteries, causing very rapid recharge rates that may make them bubble more intensely than normal? 

adam

Offline Cornelius

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Re: Why is the top of my Batteries wet ?
« Reply #2 on: March 21, 2012, 11:27:48 am »
I agree with Adam; 14.7V are the perfect max. bulk charge voltage @ 15-20deg. C., but after that, you should lower the voltage to 13.6V +/- maintenance...

Keeping the charge @ 14.7V will produce some moisture around the caps of your battery, and you probably will have to water your batteries often... (Unless your ambient temperature are @ -20deg. C, then it's perfect for maintenance... ;D )
 
Edit:
The idéal scheme are to charge your batteries up to 14.4V (@27.7C.), then reduce the voltage to 13.2-13.6V for maintenance charge.
Also; i'd say that temperature compensation are underrated. I'd like to say; add 0.15V for each 5 deg.C. below 25C.; subtract 0.15V for each 5C.above 25C. (assuming a 12V bank. (the usual spec.are  0.03V/cell/celsius.) Add when temp are below 25C. and subtract when above.)

Offline WooferHound

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Re: Why is the top of my Batteries wet ?
« Reply #3 on: March 21, 2012, 11:28:28 am »
OK ,  I tried the baking soda test and it seems to be only water.
the tops were almost dried up from what I saw yesterday.
I think I will lower my dump voltages by a tenth of a volt.

I have 225 amphours of batteries and charge at about 9 amps.
max temperature lately has been about 90f (32c)
it can get up to 105f (40c) in the hottest summers
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Offline Cornelius

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Re: Why is the top of my Batteries wet ?
« Reply #4 on: March 21, 2012, 11:42:24 am »
(You managed to post just after my reply... ;) )

I'd say 14.7 are a bit high for max bulk charge @ 32C: set it to 14.25V max. bulk, and then if you
could reduce to 13.2V, it would be idéal... :)
 
Edit:
@ 9A on an 225Ah bank, you're in no danger in damaging the bank, so you're safe. :) But keeping the high top charge voltage will lead to more frequent watering needs... ;)

Offline WooferHound

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Re: Why is the top of my Batteries wet ?
« Reply #5 on: March 21, 2012, 11:55:12 am »
I was planning on adding some wind power later so I decided to use Ghurds Dump Load Controllers to control the charge on the battery. It has 2 adjustable stages, they can be set to any threshold voltage. Stage one is selectable at 3 or 6 amps, Stage two can be 6 or 12 amps.

From your suggestions, I might set stage two at 14.25v 6 amps, and stage 1 at 14.35v 3 amps . . .
I think there is plenty of time to think about it, trying to cloud up and rain a few days
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Offline Cornelius

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Re: Why is the top of my Batteries wet ?
« Reply #6 on: March 21, 2012, 12:16:22 pm »
From what you propose, you'd charge with 6A @ 14.35V, and then with 3A @ 14.25V (assuming perfect solar conditions.); sounds perfect for your battery bank. ;)

3A into an 225Ah bank are no more than one needs to keep that bank healthy for maintenance. :)
Do not forget to manually equalize the bank every 1-3 months... *:)

Offline WooferHound

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Re: Why is the top of my Batteries wet ?
« Reply #7 on: March 21, 2012, 02:40:13 pm »
I got enough sun to get it all reset to some lower voltages. I'll explain my 2 stage dumpload charge controller more clearly and the new settings.

There is a maximum of 9 amps charging current from my solar array.
The charge controller is 2 independently adjustable dump stages.
The way I have it set now
When the battery voltage reaches 14.25 the second stage controller kicks in using PWM to pulse a 6 amp load and maintain the voltage at 14.25, this is what will be happening 95% of the time.
When ever the charging amps are higher than 6 amps, the 6 amp second stage will not be able to hold the voltage back anymore and the battery volts will creep up.
If the voltage reaches 14.35 then the first stage dump controller also kicks in using PWM to pulse a 3 amp load to maintain it at 14.35 volts.
If I add more panels or a wind generator, I can switch to higher current dump loads.
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Offline Rover

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Re: Why is the top of my Batteries wet ?
« Reply #8 on: March 21, 2012, 03:05:24 pm »
Woof,

Any chance he liquid you are seeing is from humidity?

Rover
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Offline A of J

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Re: Why is the top of my Batteries wet ?
« Reply #9 on: March 21, 2012, 03:34:30 pm »
I am with Rover on this one, your dew point is above some of your overnight temps, and ditto for the comments on dump voltage, actually highlights why controllers have three stages.

Allan

Offline kensue49

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Re: Why is the top of my Batteries wet ?
« Reply #10 on: March 21, 2012, 03:41:03 pm »
Woof,
 If you have them in the metal building in your pic's, I bet it is condensate from the temperature difference in your battery to the surrounding air.
Kenneth

Offline Watt

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Re: Why is the top of my Batteries wet ?
« Reply #11 on: March 21, 2012, 08:29:45 pm »
I agree with Rover on this one Woof.  Mine do the same thing. 

I arranged a 24v group of 8d's and GC2 batteries in my 72v array and one of the first things I noticed was the batteries cooled down from being cycled less.  From then on, the 8d's seem to be moist on top for than the GC2's. 

I'll post a pic in a bit even though they are all dry at the moment.  I don't worry about it other than it seems the terminals show signs of wanting to corrode. 
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Offline Watt

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Re: Why is the top of my Batteries wet ?
« Reply #12 on: March 21, 2012, 09:30:03 pm »
Went out to take a pic and noticed the tops are starting to get wet.  The batteries have been pretty warm today and now it has cooled down in the shed which has caused the sweating.  Anyway, hope you can tell a bit about these in this pic Woof.

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Offline Isaiah

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Re: Why is the top of my Batteries wet ?
« Reply #13 on: March 24, 2012, 05:06:41 am »
BE CAREFUL with water on top of the battery it is conductive!
 take your vom and check it out. be sure to have ventilation
 If your room is not ventilated any spark can cause a hi decibel event you don't want !
 i had a battery blow up when trying to start my small bull dozer in a small shed.
 For more info on battery's go to this link
http://www.thebackshed.com/forum/forum_posts.asp?TID=2979&PN=1
 there is 11 pages there.
I have permission to move this information to this forum but haven't had the time to do
so as yet
 if there is enough interest Ill get on it soon??
Isaiah

Offline A of J

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Re: Why is the top of my Batteries wet ?
« Reply #14 on: March 24, 2012, 02:40:28 pm »
 ::) Water does not conduct electricity, water with impurities in it may.

The top of batteries should be kept clean, true.

Hydrogen is explosive in air within the limits of 4-74% give or take a bit, true.