Hi Jim
On (19 Aug 96) Jim Dunmyer wrote to Alec Cameron...
 > On what basis do you decide to retire an aged battery? If you 
 JD> When it won't run the UPS for any length of time. I always attempt to
 JD> charge it with my regular battery charger first. This last time, I 
ooled
 JD> around for several days and couldn't get the one battery to hold over 8
 JD> volts under load.
My approach would be to give it three discharge- recharge cycles at c/10. If
there was no useful improvement ie increasing capacity at each cycle, I would
retire it.
 JD> Everything I've read says that batteries should be given a periodic
 JD> equalizing charge of between C/10 and C/20, so 5 amps is enough for my
 JD> 100AH batteries. The idea is to get all the cells gassing freely for 
ome
 JD> time in order to be certain that all cells are fully charged.
Yes. Otherwise a couple of cells in the string rapidly give up on discharge. 

chain is as strong as its weakest link!
 JD> I'm also beginning to feel that cycling (discharging) the batteries once
 JD> in a while might not hurt them. Perhaps run the UPS for 15 or 20 minutes
 JD> every now and then. Give them an equalizing charge afterwards.
I agree. Once a year, I discharge each of our car batteries then recharge.
Typical lifetimes are three to six years.
Thanks for your other informative comments.  Cheers....ALEC
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