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monitoring software.
Set the UPS shutdown time to 2 minutes, all other settings to
nominal, and disconnect the serial port cable from the UPS be-
fore running the recalibration. If you leave a monitoring program
running through the serial port, it will turn the UPS off early,
and you don’t want to do that during a recalibration run. When
the run is complete, and the UPS turns off, you can reattach the
serial cable, and the normal loads, and recharge the batteries
normally. If you think you might have a power outage during
the recharge time, allow the UPS to recharge to 20% or so (in-
dicated by the panel lamps) before trying to use the computer
system. This will allow the UPS to handle short dropouts while
it recharges. Of course, if you can leave the computer off during
the recharge time, the UPS will recharge much faster.
As an aside, when the batteries failed, my total runtime at
100% charge and an idle state was 9 minutes, which is pretty
bad. I replaced the batteries with extended capacity cells, which
add about 15% to the stock capacity. Now, after two complete
charge/ discharge cycles, 100% charge shows the available run-
time to be 42 minutes on the system when it’s idle, and 33 min-
utes when the system is very busy. The differences are due to the
load of the computer, when the disks are busy, and the cpus are
not in a halted state (my system halts the cpus when they are
idle, to save power and lower heat, as do other OS like Linux),
when compared to an idle state. Apcupsd indicates the load is
about 27% when idle, and as much as 37% when heavily loaded.
I’ve found that two charge/discharge cycles result in a more ac-
curate recalibration when installing new cells. It appears that
some batteries need to be put through a couple of complete cy-
cles before they reach their full capacity. I’ve also noticed that
the full-charge voltage is different for each battery until they
have been through two cycles. On the initial charge of my new
batteries, the 100% charge voltage on the two cells was almost
.5 VDC apart. After two complete cycles, the batteries measure
within .01 VDC of each other!
I hope this information helps anyone who might encounter the
problem I saw, and also shows folks how to recal their batteries.
If you haven’t done a complete recalibration in a year or two, I’d
recommend it, so that you have warning of a low battery instead
of what happened to me.
Regards,
—Carl
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