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Jun 23, 2009

APC Smart UPS 750 - Hot Swappable Batteries?

by J. Robert Burgoyne — last modified Jun 24, 2009 02:50 PM
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Although a user can replace the batteries in a Smart UPS 750 without turning the unit off, in our case clearing the replace battery warning requires power-cycling the UPS, which cuts power to the devices you have plugged in and are trying to protect.


UPDATE - June 29, 2009 - The APC Smart UPS 750described below figured out its battery had been replaced, and now gives the correct status message, without power-cycling.

True Blade Systems has been using APC UPS products for many years. They're reliable, integrate well with our Linux servers and we've generally been pleased. We run apcaccess and apcupsd to monitor what's going on with the UPS. 

But a recent experience with a battery replacement in an APC Smart UPS 750 left us asking the following question:

Why make the UPS' batteries hot-swappable but NOT clear the battery warning indicator upon replacing the old batteries?

APC's technical documentation for this unit notes:

"This UPS has an easy to replace, hot-swappable battery. Replacement is a safe procedure, isolated from electrical hazards. You may leave the UPS and connected equipment on during the replacement procedure."

The above is true. Although I was a bit afraid to swap the batteries without turning the unit off, nothing bad occurred during the swap. But replacing the battery module (actually two batteries) did not clear the Replace Battery LED on the front panel. 

So I waited a day to see if time would clear the LED, but the LED stayed on. 

Thus on June 24, 2009 I called APC on (800) 555-2725 and spoke with a support rep. The support rep informed me that to clear the Replace Battery LED I must power-cycle the UPS. For me that means I must also power-cycle the server that's plugged into the UPS, which is not acceptable for me. So I'll have to wait for a weekend night to power-cycle the UPS. 

The rep created an internal case for future reference, case #C1-1041119483. 

Here are some other relevant details from apcaccess, the Linux based program we use to monitor the UPS:

APC      : 001,040,1009
DATE     : Wed Jun 24 14:36:56 EDT 2009
HOSTNAME : kenya.[deleted]
RELEASE  : 3.12.4
VERSION  : 3.12.4 (19 August 2006) redhat
CABLE    : USB Cable
MODEL    : Smart-UPS 750
UPSMODE  : Stand Alone
STARTTIME: Sat Jun 20 13:40:37 EDT 2009
LINEV    : 123.1 Volts
LOADPCT  :  24.7 Percent Load Capacity
BCHARGE  : 100.0 Percent
TIMELEFT :  36.0 Minutes
MBATTCHG : 5 Percent
MINTIMEL : 3 Minutes
MAXTIME  : 0 Seconds
OUTPUTV  : 122.4 Volts
DWAKE    : -01 Seconds
DSHUTD   : 090 Seconds
LOTRANS  : 106.0 Volts
HITRANS  : 127.0 Volts
RETPCT   : 000.0 Percent
ITEMP    : 35.5 C Internal
BATTV    : 27.3 Volts
LINEFREQ : 60.0 Hz
LASTXFER : No transfers since turnon
TONBATT  : 0 seconds
CUMONBATT: 0 seconds
STATFLAG : 0x07000088 Status Flag
SERIALNO : AS0721121024
BATTDATE : 2009-06-18
NOMBATTV :  24.0
FIRMWARE : 51.13.D USB FW:7.3
APCMODEL : Smart-UPS 750
END APC  : Wed Jun 24 14:37:04 EDT 2009

Let us know if you have had a similar experience with an APC or other manufacturer's UPS.