We have huge clear Exide batteries in our telephone central office in series and they last forever. Once a week they are hydrometer tested and adjusted with acid/water and are constantly monitored electronically. As big as stereo speakers.
I always find the CO battery vault/room a little eerie. You can smell the acid. Always feel like I'm breathing in cancer - even with a mask on. Been here for 30 yrs and I'm not dead yet, so it must be in my head.
