UPS Stands for Uninterruptable Power Supply, and as the name implies, they are uninterruptable. They are also called battery backups and are used for powering sensitive computer equipment in case of a power outage. They also regulate input voltage and protect against power surges.

Battery backups come in many different sizes between the size of a small car (for large data centers) to something that looks like an oversized power strip (for your home computer). Mine is in the middle ground between giant and small, and it is rack-mountable (that’s why it’s so flat).

This one appeared in one of my first blog posts, and it takes two 6 volt lead acid batteries wired in series for twelve volts. This is where the problems start. You can find these battery backups for free because they just have a bad battery. Why? Because the manufacturer of these power supplies will put their logo on a standard battery and sell it for 10 times as much as it cost them to buy. If you get the information off these “inspected and approved” batteries you can usually find the exact same kind for much, much less. Most people don’t know this, so they find it more economical just to get a new battery backup. For me, a new battery pack authorized by APC would run me $200. That’s not going to happen, because if I bought both batteries on it would cost less than $40 dollars.

I’m not in desperate need of a UPS, but I would like to have mine working so it’s more than just a beeping paperweight. So, I decided to go and try to fix it with stuff I had laying around. I have two 12 volt lead acid batteries that I wired in parallel, not in series. If I wired them in series, I would get 24 volts out, which would fry the control board. In parallel, it increases the battery capacity but keeps the voltage at 12. So, with this setup, I was expecting to get a longer run time than with just the regular batteries.

I was a little afraid to power it up because the batteries might damage the power supply, but after I did, the “replace battery” light didn’t come on and everything functioned as it should. I’ll need to leave it plugged in for a few days to be sure everything works, so I’ll upload a new post if there’s a battery leakage or power supply burnout.

The large batteries wired together.

I cut a hole in the plastic to accommodate the wire to the batteries.

No fault lights!

The old flat battery pack.

I didn’t feel like soldering, so lever nuts it is.

The big inverter transformer

The UPS is rather empty inside.