Battery Bank

[africanamber]

Hey there, I was hoping to get a response in regards to battery bank testing and maintenance for DC supply in a Substation, switch yard. Many years my company has done impedance and ripple current testing annually and a discharge testing about every five years. When completing impedance testing and verifying voltage reads from every cell within that bank, if the cells are out of range (lowest to highest) 5% of each other we are given the go ahead to do an equalize charge for whatever the manufacturer specify's (48 hours normally). After said charge and a day later, we go back and check individual cell voltages. Most of the time the cells voltages are about the same, but within a month they are back to being + - 1.5% to 2.5% differing in cell voltage, 2.17vdc cell could be as low as 2.11 or high as 2.23 or higher. I am to the point where I think, if we aren't doing discharge testing every year, that turning the AC charger off for a discernible amount of time would really be exercising all the cells equally, in theory, essentially. If we have a bad cell it would be distinguishable when turning the charger back on. I am thinking preventative maintenance but the employer believes otherwise. Just want some feedback on what other people are doing with their battery banks. Thanks in advance