Battery Electrolyte Level

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gathermewool

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Clif Notes Version: How do you know how much distilled to add to battery cells? I posted before, how the 51R-size battery in my Civic had electrolyte level just below the lead on one cell before charging it from dead. I didn't have to add much to bring it up to just above the plates, but that's all I did, raise level to just above the plates and then charge the battery. After the battery was fully charged, I filled each cell with distilled water to between what I'm assuming are the high and low level indications. What I'm assuming is the level indication, are the two C-shaped plastic pieces that dip into the electrolyte of each cell's fill hole. I'm assuming the bottom of the plastic pieces is the min level for electrolyte. At a higher level, the these opposing Cs join. I'm assuming this is the max level, which still gives some margin for expansion to the top of the fill hole. // I actually noticed the same thing in the stock battery for the Subaru, though the distance from the top of the plates to the bottom of the plastic pieces is larger. I want to add distilled water to the Subie's battery, but I want to make sure that the level should be, post charge, measured in the way I mentioned above. This post should illustrate what I'm talking about:
 

gathermewool

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Originally Posted By: Charlie1935
I add just to the bottom of the split.
Yep, that's pretty much what I did for the Civic's battery (except I added to just above that split) and intend to do for the Subie's battery, unless someone chimes in with better advice.
 
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Originally Posted By: gathermewool
Originally Posted By: Charlie1935
I add just to the bottom of the split.
Yep, that's pretty much what I did for the Civic's battery (except I added to just above that split) and intend to do for the Subie's battery, unless someone chimes in with better advice.
A Google search shows that you are correct in first only filling to just above plates (if low), then charging it. Various sources say after charging, then fill to 1/4 inch below the vent well, 1/8 inch below, or just barely touching the bottom of the vent well, depending on who you want to believe.
 

gathermewool

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Originally Posted By: doitmyself
Originally Posted By: gathermewool
Originally Posted By: Charlie1935
I add just to the bottom of the split.
Yep, that's pretty much what I did for the Civic's battery (except I added to just above that split) and intend to do for the Subie's battery, unless someone chimes in with better advice.
A Google search shows that you are correct in first only filling to just above plates (if low), then charging it. Various sources say after charging, then fill to 1/4 inch below the vent well, 1/8 inch below, or just barely touching the bottom of the vent well, depending on who you want to believe.
Awesome, thanks. My Google-fu must be weak, because I searched various terms and came up with only very general information. I just got in my cheapo hydrometer (sp).) I'll check SG to figure out whether I've overly diluted when I get the chance.
 

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Just keep the plates covered then there will be less electrolyte boiled onto the top of the battery.
 

gathermewool

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So, with the Subie battery topped off charge-wise I prepared to add electrolyte. Funny thing - the case is opaque plastic, and with a flash light shining on the battery, I realized that you can barely see the battery level; darned near impossible, is what I'm saying. Upon VERY close inspection, I was able to clearly see an UPPER LEVEL line and a LOWER LEVEL line for electrolyte level range...I'm exaggerating, of course, to make up for how dumb I feel. The lines are pretty clear. Before adding any water, it was near the LOW line. I added water to 80% of the way up to the UPPER LEVEL line, which was the level just a fraction of an inch above where it touches the vent well (the plastic that dips down into the fill port.) This confirms that, at least for this battery, a level BELOW this point is still well within band, and touching the plastic vent well sides is near the top of the band.
 
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Originally Posted By: CT8
Just keep the plates covered then there will be less electrolyte boiled onto the top of the battery.
This ^
 
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Originally Posted By: slacktide_bitog
I've never needed to add water to a battery
How old are you? I service a lot of batteries at the Military base where I work. I have gone through 10 gallons of distilled water in the last 3 years. I get the water in 5 gal jugs. Some of the batteries are in golf carts and they really go through it fast. I have people call me when they have any kind of problem battery related. I used to service about 30 generators and they had two batteries each. As a matter of fact I am sick and tired of batteries.
 

gathermewool

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Originally Posted By: slacktide_bitog
I've never needed to add water to a battery
How many flooded lead-acid batteries have you owned? How often did you check the level? For reference, the Subie is over two years old and was still above the lower end of the level band. It's a big battery, though, and took a decent amount of water to get it near the top of the level band.
 
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You want the level just below those wells. They're there to reduce electrolyte from "wicking" up to the top of the battery. If you bring the level up and make a meniscus you greatly shorten the path to the outside.
 

gathermewool

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Originally Posted By: circuitsmith
You want the level just below those wells. They're there to reduce electrolyte from "wicking" up to the top of the battery. If you bring the level up and make a meniscus you greatly shorten the path to the outside.
I would think that that full contact might have some effect if the cross section were fully closed off, but not with this geometry; that is, unless you're saying electrolyte will wick up a wall of plastic.
 
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I was asked once as an electrician in a soybean plant to come look at he battery chargers. They thought they were bad as the batteries would not get charged enough. When they topped the batteries off they over filled and over time weakened the acid strength. So when they charged it pushed acid out the top. Every drop of acid that gets replaced by water weakens the strength of the electrolyte when fully charged. That was the problem there. And the lower gravity acid will boil a lot sooner too which just further makes things worse. I always keep the minimum amount in the battery. As long as the plates do not become exposed you are good. And there usually is a 1/4" or so below the top of the separators before hitting the battery plate.
 
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Originally Posted By: gathermewool
I would think that that full contact might have some effect if the cross section were fully closed off, but not with this geometry; that is, unless you're saying electrolyte will wick up a wall of plastic.
That's exactly what I'm saying. Sulfuric acid is a strong creeper. Those sleeves encourage the liquid to gather at the bottom edge and drip back down into the cell.
 

gathermewool

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Originally Posted By: Donald
If you fill it up so it just touches the bottom of the wells, how long before its say 1/8" under the bottom which is what you want?
Are you asking how long it takes for the water to evaporate and for the electrolyte level to drop 1/8" below that point? If so, I'm not sure. I check often and very rarely feel that I have to add water. I've never added to the Subaru's battery, assuming that the plates being covered is good enough. I added a few oz, total, to all cells, to bring the levels up to near the top of the band. I'm hoping I won't have to add any water between now and when the battery needs to be replaced.
Originally Posted By: SHOZ
I was asked once as an electrician in a soybean plant to come look at he battery chargers. They thought they were bad as the batteries would not get charged enough. When they topped the batteries off they over filled and over time weakened the acid strength. So when they charged it pushed acid out the top. Every drop of acid that gets replaced by water weakens the strength of the electrolyte when fully charged. That was the problem there. And the lower gravity acid will boil a lot sooner too which just further makes things worse. I always keep the minimum amount in the battery. As long as the plates do not become exposed you are good. And there usually is a 1/4" or so below the top of the separators before hitting the battery plate.
The distance from the bottom of the vent tube pieces and the top of the plates in my Subaru's battery is more than 1/4". The top of the plates also seems to be below the low level marking on the battery. Just at the plastic level pieces is near the top of the indicated level band. 1/8-1/4" past where the plastic dips into the electrolyte is the top of the indicated level band. You're right, diluting isn't good, but the different in level between the top top of the fill ports and where the plastic dips into the electrolyte is a relatively large amount.
Originally Posted By: circuitsmith
Originally Posted By: gathermewool
I would think that that full contact might have some effect if the cross section were fully closed off, but not with this geometry; that is, unless you're saying electrolyte will wick up a wall of plastic.
That's exactly what I'm saying. Sulfuric acid is a strong creeper. Those sleeves encourage the liquid to gather at the bottom edge and drip back down into the cell.
Ah, gotcha. This is probably more of an issue for the Autocraft battery than the Subaru's battery, since the former has two three-port caps, with only a plastic-to-plastic seal; whereas, the Subaru's battery has six gasketed vent caps.
 
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