water on battery tops

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water on battery tops

Postby Megunticook on Wed Feb 06, 2019 10:19 am

I've had these Rolls S-550 batteries for a little over a year now, just wanted to compare notes with others on some observations.

Typically when I check on them (monthly), I notice a little water on the tops of the batteries. Not a lot, but enough to wipe up with a dry rag. At first I thought it might be just condensation (the batteries are in an unheated space), but now I don't think so.

The bank is only occasionally discharged (every other month), most of the time it sits fully charged and floating during the day while I "sell" power to my main AC panel and the grid. I keep a pretty close eye on the voltages and stick with Rolls recommendations (58.8 bulk/absorb, 54 float, not factoring in temp. compensation).

The caps are all on tight but I believe are designed to vent a little bit. Is this electrolyte I'm seeing?

Electrolyte levels are generally 1/4-1/2" below the bottom of the filler necks in each cell, which is what Rolls recommends. I didn't add any water at all for the first year, then just a small amount last month after an EQ cycle.

On a secondary note, I noticed a slight decline in s.g. when I checked last night, which is the first time I measured since adding that water last month. Seemed like s.g. was mostly 1.260 (a handful of cells ranged up to 1.280). Before the water addition, s.g. was more clustered around 1.270 or 1.275 (ranging up to 1.285).

Is the s.g. decline because I added water? Is electrolyte escaping out the caps somehow? Curious to hear others' experiences on this.
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Re: water on battery tops

Postby JRHill on Wed Feb 06, 2019 12:12 pm

There have been several threads lately regarding batteries that really don't do anything but sit there and float.... To me, this low use maintenance has to be harder than working them every day. To me, a bi-monthly std discharge/recharge isn't enough and whacking them with a heavy, deep discharge and heavy charge isn't going to happen in that same cycle. Somehow you have to work them harder for the sake of longevity.

The water on the tops? Grab your mate's favorite jeans, cut out a few squares and mop up the liquid. If the squares disintegrate in a few days then you know if its acid or else its humidity ;-)
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Re: water on battery tops

Postby raysun on Wed Feb 06, 2019 3:13 pm

To avoid a denim war, you can take a pinch of baking soda and dissolve in a few ml. of water. Put a drop or two in the puddle on the battery. If it foams like mad, there's acid present.
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Re: water on battery tops

Postby sparksalot on Wed Feb 06, 2019 4:04 pm

H2SO4 has quite a higher temp. to form into vapor and then to condense back to liquid.

Think salt water evaporated and condensed back into drinkable water...salt stayed behind...
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Re: water on battery tops

Postby Shadow_Storm56 on Wed Feb 20, 2019 5:25 pm

Mine stay in float alot but have not had any capacity issues or change ever.
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Re: water on battery tops

Postby raysun on Wed Feb 20, 2019 5:43 pm

Anything that can cause splashing including bubbling electrolyte and battery vents can bring a solution to the battery surface. It may be deposited water vapor, or it may be something else.
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Re: water on battery tops

Postby Shadow_Storm56 on Wed Feb 20, 2019 5:45 pm

Plus one tiny drop of acid will spread out and make a big wet spot that never evaporates. My battery tops are wet just from the odd split drop of acid when I do the sg test
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Re: water on battery tops

Postby sparksalot on Wed Feb 20, 2019 11:11 pm

Shadow_Storm56 wrote:Plus one tiny drop of acid will spread out and make a big wet spot that never evaporates. My battery tops are wet just from the odd split drop of acid when I do the sg test



Good point about that acid will never evaporate as always does the plain old water.
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