APC BackUPS 500 (BK500M), no workie?

[Anonymous user]

I got one of these as a "gift" from a computer client I am working for.  "Good" is written on a sticker on the top of the case, but... me no think it so good.  😄

If it's plugged in, the test alarm works, the green power LED lights up (in the ON position), and anything plugged into the battery backup plugs, works when I turn it on.  However, after leaving it plugged in overnight (10 hrs. at least), and unplugging it, when I turn it on, the green LED does NOT light up, and the test alarm does NOT sound, and anything plugged into it does NOT power on at all.

Upon removing the battery and doing a simple Multimeter test, I get about 1.5V showing.  Shouldn't it be 12V?

Is the battery dead or is the unit not charging the battery?  Given this unit is rather old, in and of itself (what computers still have 9-pin serial ports?), I don't want to invest any money into it, if it's really not worth it, overall.  How can I be sure this unit is still "properly functional" and buying a new battery wouldn't be a waste of money?  What is the charging voltage out of the red/black wires connected to the battery?  Does the UPS charge the battery whenever AC is connected?

I look forward to some answers, to see if this unit is just trash can fodder (I plan to recycle the battery at least) or a usable device, with a new battery.