Friends:
Here is a conundrum I have often pondered. Maybe someone can solve this for me: Flooded cell O&M manuals instruct not to top off battery electrolyte levels before equalizing. They also instruct to check SG before adding water. Imagine two identical cells, one low on water, but above the moss-guard, and one at the recommended level. You equalize the array and then check the SG on both. I am imagining that if the cells were equivalent in capacity, they have the same amount of acid. However if one has less water, it has a higher ratio of acid to water, therefore it will read higher in SG. If the above is true, it is not accurate to compare the SG in cells unless the water level is equal, or close to. If you were to add distilled water to the cell that was low, the water would not immediately mix thoroughly. Then to accurately compare SG, you need to wait some time after watering and you would need to be somewhat accurate in keeping all cells at the same water level. How long would this be? Checking SG is but one part of flooded cell maintenance. My monthly procedure is this: 1. Check to see if water is above moss-guard on all cells. (I sometime skip this if I am confident the cells historically do not dry out in one month.) 2. Initiate an EQ charge cycle. 3. Shortly after the EQ cycle, check and record SG in all cells. 4. Re-water batteries to correct level. The above takes long enough. If I have to add water and let it mix before I test SG, the process takes even longer. Nonetheless, I want accurate results. My advice to clients and actions taken are dependent on these readings. Anyone have any wisdom to pour in? I am going to experiment to see what I can learn. William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985
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