Battery rant

[PaulAm]

I had a power failure this morning that put all my systems on the UPS.  When my monitor told me I had 30 minutes left I started shutting down systems.  This was not a big deal, normally, but all of a sudden the batteries just died.

Well, I was expecting this and I had a couple of replacement batteries sitting on the shelf.  Just plug them in an go, right?  No, after putting them in, the UPS wouldn't start.  I took them out and put in the old batteries and pried off the end covers so I could charge each of the 12V batteries in the pack separately.  When I did that I found one of the battery connectors had been wired up in REVERSE!  Fortunately, the two packs are put in series to get 48V ( 2 packs of 2 12V batteries) so in
this case I got 0V.  Things would have gotten interesting if they were paralleled

Moral: don't assume a brand new battery pack is correctly assembled without testing it first.