mattlach

Active Member
Aug 1, 2014
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Hi Everyone,

There really isn't a subforum for UPS:es and other power solutions, so I decided to post here.

I bought a couple of APC SMT1500RM2U units for my rack used on ebay last year. The seller put fresh batteries in them before selling them, and they have gone from 50 minutes of runtimes when new in August last year, to absolute trash, sub 5 minute runtimes now.

There are three potential contributors to this short battery life from what I can tell:

1.) Were they just cheap garbage batteries?

2.) Was the high heat (30C-35C) environment they were running in killing them early?

3.) Is this a symptom of APC's notorious high float voltage problem, which kills batteries early (presumably on purpose, because their Schneider overlords want to sell more batteries)?


I have since addressed the high heat. Older server room (lol, closet) had no options for cooling. New one in the new house does.

I also plan on trying to buy decent batteries this time around (but is it just m, or have they become really pricy? Batteries Plus used to be affordable, but now 12V 8AH batteries are $40 each, and I need 8 of them!)

From various sources I have read that on older models of APC UPS:es you used to be able to configure the desired float voltage via hidden configuration settings, over a serial interface. Does anyone know if this is still possible with the newer SMT1500RM2U's I have?

I appreciate any suggestions!
 

mattlach

Active Member
Aug 1, 2014
184
26
28
So, upon a 8th googling of the same terms, I randomly came across this page which never popped up before.

Some reading of this page, and the linked reference page has resulted in the following conclusion:

There is a proprietary RJ45 Serial interface port on the back of these things (requiring a specialty RJ45 to RS232 cable), but apparently it is no longer connected for "SMART" functionality like the old ones, so it cannot be used to - among other things - reprogram the float voltage.

That said, the funtionality is still in there, and there is still a header on th econtrol board, so you just need to pop it open and connect your own.

Looks like it is relatively simple. (Just don't touch anything high voltage!) All I need is a cheap TTL USB to serial adapter ($5 on amazon) and some female to female breadboard jumper wires.

I'm going to give it a shot.