APC Smart-UPS battery change

My home Linux box is always on and to make sure it stays on I have an uninterruptible power supply for it. APC is very well supported in Linux by open-source apcupsd. Pretty much all other UPSes are supported by NUT, but for some strange reason APC has a separate project.

Update 20th May 2018: There is a new post about APC UPS batteries here.

Couple days ago the UPS started to beep. My house had electricity and there was no apparent fault. Except that I got an e-mail from apcupsd "UPS battery needs changing NOW". Aow crap! The batteries had reached their end of life. I confirmed the status with apcaccess and got status of:
STATUS : ONLINE REPLACEBATT NOBATT

Every 12 hours, the UPS releases a burst of beeps and I find that very annoying. It was time to go shopping for new batteries. Luckily my unit uses Replacement Battery Cartridge #7, which is popular and generally well available and the price ~200 € isn't too bad. The next thing is to get the old ones out and new ones in. APC user's manual says that battery pack is hot-swappable, so it should be an easy thing to do. Apparently the first thing to do is remove the front cover:

It has nice holes on the sides. I guess the idea is to put your fingers into them an pull hard.

When the front cover is loose, a ribbon-cable and a metal cover is revaled.

There are two phillips-head screws to hold the metal cover in place:

When the metal cover is removed, the battery pack is visible:

There is a plastic tab at the bottom. I guess it is there, so that batteries can be pulled out. Now that the metal cover is removed, the batteries are not attached to anything:

The final thing to do is to disconnect the battery pack:

Now the UPS keeps beeping a lot. It is annoyed by the fact, that it cannot find a battery. Since I don't have any original APC software on my computer I found out that the audible beep can be silenced. First make sure that the apcupsd is not running:
systemctl stop apcupsd.service

Now the apctest can be used to change any of the UPS-parameters:

Current alarm setting: ENABLED
Press...
 E to Enable alarms
 D to Disable alarms
 Q to Quit with no changes
Your choice: Select function: d

New alarm setting: DISABLED

Now there is the blissful silence. It is much nicer to operate with the new battery pack.

Obviously the idea is to reverse the instruction. Connect the new battery, slide it in and tighten the screws and attach the front cover back.

I guess, the new battery should last at least 3 years before I'll be getting a completely new UPS. There simply is no point in running a really old UPS with brand new batteries. I guess the UPS technology will still evolve so that a new tech is required after half a decade.