Hi,

When filling my battery cells,

in some cases, cells in the same battery will have varying water
levels. Not a dramatic difference, but definitely noticeable.

What is the explanation for this?

Thanks,

Mike.

"beaufortnc" wrote in
oups.com:

in some cases, cells in the same battery will have varying water
levels. Not a dramatic difference, but definitely noticeable.

What is the explanation for this?


When charging a lead-acid battery, gassing starts around specific gravity
1.250-1.270 in a normal cell. As the battery ages, "sulphation" takes
place in all the cells as the acid and lead is converted into lead sulphate
in the process of discharging. This conversion is how you get to steal
electrons to use from it.

Unfortunately, lead sulphate ions have a tendency to attach to each other
forming lead sulphate crystals, which are very stable (also unfortunately).
This happens worse if the battery is left in a discharged state for any
period of time....when there's lots of lead sulphate ions in the
electrolyte. Once formed into crystals, these heavier-than-the-acid
crystals drop out of the solution into the bottom of the battery in a space
the battery manufacturer left for them. They can no longer be converted
back into acid and lead metal by charging the battery.

Some of the cells less sulphated will charge up to 1.250 or more. More
heavily sulphated cells will not reach this goal and "charge up" more
quickly to a lower level. Once they reach this lower level, that cell
starts converting its water dilutant into hydrogen and oxygen gasses and
heats up, forming gas molecules you can see "perking" if you look into the
holes, assuming it has holes any more. The water is used up more quickly
in these cells and you find their levels dropped further than the good
cells...You may even find them quite below the plate tops. The battery is
growing old and should be replaced before it strands you in the dark. It's
capacity is much lower than it should be.

Buy a temperature-compensated hydrometer from an auto parts place. It has
a little thermometer calibrated to add or subtract from the reading of the
float. This is the ONLY way to tell what the condition of each cell is in
your battery bank. Open the hole, dip the rubber tube into the cell, suck
up the electrolyte (BEFORE ADDING WATER) and let it sit a few minutes so
the thermometer has time to respond to its electrolyte temperature. Make
sure the float is free to float and read what it says. Subtract or add
what the calibration on the thermometer tells you to and that is that cells
specific gravity at this moment. Ideally, they should all be the same,
around 1.260 is a fully charged battery. 1.120 gravity is discharged, even
a little too low for good battery life. Search Google for lead acid
battery maintenance and there are gravity charts you can print out showing
you % charge against specific gravity reading. If any cell is over 30
points lower than the others, it will be the cell that goes dead first, and
that will be the limit of that battery's AH rating. "Adjusting" the
gravity on a NEW battery by adding electrolyte or subtracting electrolyte
and replacing it with DISTILLED ONLY water over a small range is fine.
Don't try this on an old battery. Adding acid to that bad cell just eats
holes in the plates and you accomplish nothing. The acid "runs down"
first, before the plates are eaten, on purpose so you can charge 'em back
up.

Don't put aspirins in there, either......geez....

--
Larry