It will take 5 minutes to finger the bad one.  At least if you are going to 
change them all, don’t toss the good ones.  Just kill the power and take 
voltage readings.  The good ones will all read similar.  Bad ones drop quickly. 
 

From: Josh Luthman 
Sent: Tuesday, December 29, 2020 2:03 PM
To: AnimalFarm Microwave Users Group 
Cc: Chuck McCown 
Subject: Re: [AFMUG] Custom batteries on APC Smart UPS 750XL

Well I'm just going to replace all 4 of them then (12v batteries wired for 
24v).  No sense in trying to figure out which one is bad IMO - $300 and a 
wrench I'll be done in an hour. 

Thanks for the sanity check!


Josh Luthman
24/7 Help Desk: 937-552-2340
Direct: 937-552-2343
1100 Wayne St
Suite 1337
Troy, OH 45373


On Tue, Dec 29, 2020 at 3:53 PM Chuck McCown via AF <[email protected]> wrote:

  Yes, best to periodically discharge it and take volts per cell or volts per 
battery every few minutes.  The bad cell/battery will start to make itself 
evident very quickly.  I have a charger setup that does this for me 
automatically.  

  From: Josh Luthman 
  Sent: Tuesday, December 29, 2020 1:48 PM
  To: AFMUG 
  Subject: [AFMUG] Custom batteries on APC Smart UPS 750XL

  These batteries: https://www.batteriesplus.com/productdetails/97=479=1 

  I first installed this system just under 6 years ago.  We've lost power a 
couple of times, but only for a short while (30-45 minutes).  I remember it 
saying something stupid like 7 hours of run time.  I have no idea how APC 
calculates this. 

  Today we had another outage, where a phase went out, and it switched over to 
batteries again.  It said something like 30 minutes of run time!  Luckily I ran 
upstairs and after 10-15 minutes, it was really pissed that it didn't have 
power and angrily beeped that it was nearly ready to give up (at which point I 
put it on the generator).

  After a few hours we got utility back up and I moved the UPS back over.  
After lunch I wanted to test the battery voltages, but in the 5 seconds it was 
unplugged it got really pissed again so I plugged it back in.

  With the charger on it, each battery individually is showing me 13.83v.

  In the first 10 minutes of the day without power, battery voltage went from 
27.6 down to 22.36.  This confirms I have at least one bad battery, right?  The 
load is roughly ~83 watts according to the UPS.


  Josh Luthman
  24/7 Help Desk: 937-552-2340
  Direct: 937-552-2343
  1100 Wayne St
  Suite 1337
  Troy, OH 45373

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