Equalizing 6 Volt battery bank

[GrampaKoot]

When I do monthly battery battery bank equalization procedure one battery always requires water addition. It is always the same battery. Is that common?
Could I impose on somebody to educate me as why it is always the same battery?
I have 4 Trojans

[Son_of_Norway]

One of the rubber seals on the cap might be problematic and leak a little bit. If so it will lose some electrolyte through evaporation. I have that problem with one of my golf cart batteries.

[BoonHauler]

Call Trojan and ask them .....

[Sam_Spade]

What exactly are you doing in hopes of achieving "equalization" ?

If you are putting a boost charge on each of the 4 batteries individually, that means that the one requiring the water is being over charged.....maybe because it has a partially shorted cell. Or that it has aged faster and the charging current isn't producing the desired result anymore.

Come to think of it, if you are boost charging the whole string, the result might be the same for the above two mentioned faults too.

P.S. Why do you think it is necessary.....or desirable even.....to "equalize" them that often ???