Back UPS Pro 1300(G), this must be a design flaw for these tower type systems.

[Poomba1]

I've replaced many a battery on many models, including the enterprise network systems (I am joyfully retired now) & I have found a disturbing issue with these Back UPS models & battery swaps. I have 2, a 1300 & 1500, replaced the batteries on both once again though this time I was not able to salvage the "this way up" sticky place cards that attach to the outside of the battery packs that have the tabs to pull the out when it is time to replace again. No biggie right, just some duct tape to keep batteries connect will be fine right? Nope! I am continually getting "battery disconnected" error messages & clicking sounds (as I see the visual battery status bar goes all the way to 100 -> 0 continually). So many reads I see people telling me to clean the connectors, crimp the connectors, wire brush this, why not solder & weld while am I at it right? Simpler solution, turn it upside down & the battery no longer is in disconnect status. So there is enough "play" in the space between the bottom removal covers & the way the battery pack slides down to the connectors that over time/age there can be enough of a gap to issue this "battery disconnected" error message. I am looking at ways to wedge (duct tape internally lasted for 1 day) the bottom of the pack against the removal door so when it is right side up, there is no gap for gravity to do it's work & disconnect the battery pack. For this to even occur speaks of a design flaw, easily fixed by turning it upside down to ensure connectivity, it rules out loose connection cables to the batteries themselves or the connection apparatus that brigs the batteries together in series. Certainly given the age of these units I cannot be the only one to come across this annoying conundrum?

[RyanG32]

I also encountered this issue when I mistakenly purchased a APCRBC123 insteada of an APCRBC124 since the last one has a bigger size and capacity than  the  APCRBC123  when standing the  UNIT up the due to the weight of the battery it gets disconnected.  I used to put some kind of padding to make it work so that there is less play for the battery until I decided to purchase the correct battery and that was more than 5 years ago I already have a newer Back UPS Unit with Pure Sine wave now that has a different battery design.