Replacing the battery on a CyberPower UT650EG and UT850EG UPS

Back in 2022, I gave the CyberPower UT650EG a try.

At the end, I mentioned:

What I’m concerned about is the battery. The specifications say that the battery is not user replaceable. I hope that this is simply something the legal team thought of to avoid any liability when dealing with users who messed this process up.

4 years later, the UT650EG battery does not seem to hold a charge, so it’s time to replace it, for real. At the same time I also decided to do the same for an UT850EG that I got in the second half of 2022.

And yes, as the title mentions, you can replace the battery on these UPS-es, but I advise you to take every precaution that you can take:

• do it when the battery is empty
• double-check the first point
• remove the fuse at the back, look for a small flat-head screwdriver shaped slot and unscrew it
• use rubber gloves
• don’t touch anything but the battery and the power cables connecting to it
• don’t use metal prying tools
• keep cats and children away during the event
• ask your partner to keep an eye on you

The process is reasonably simple:

• remove the four screws from the back of the unit, next to the power outlets
• remove the three screws from the bottom
• lift the back panel off, then gently pry the side cover off
• you now have access to the battery!

The power cables coming from the battery may feel stuck, so you will need to use a little bit of carefully applied force to disconnect the cables from the battery terminals. For connecting a new one, ensure the connectors fit snugly and don’t come loose with a little bit of wiggling.

The process is the same for both units.

The only obvious difference between the two units seems to be the battery. The plastic case supports using both the smaller and larger battery, and as long as you use ones with same voltage and at least the same amperage, you can put anything here that fits. This will have an impact on the battery runtime, but if you’re someone like me and bought the wrong replacement battery for this unit, then this does serve as a bit of a saving grace.

With UT850EG, the power cable alignment was slightly trickier with the smaller battery, but workable.

To find a replacement, I had the luxury of just bringing the old battery with me and walking into an IT shop where I picked one up based on the physical dimensions and matching specs. The capacity of the replacement battery was a bit lower, but for 13 EUR a piece I did not mind it at all.

For UT650EG, the battery size is 70x90x101mm.

For UT850EG, the battery size is 151x65x94mm.

Looking back at the experience with an APC Smart-UPS 750 and these CyberPower units, I’m not sure if getting the CyberPower units was worth it. Sure, they’re more power efficient, but I expected them to be more gentle against the batteries, which they were not.

At least I’ve confirmed that the battery replacement isn’t that scary if you take the precautions, but the APC one feels physically much more solid with a humongous metal case, the batteries just slot in the front, and the USB port and its readout actually works well enough that I can write a custom Prometheus exporter script and monitor it.