Dell XPS 13 boot loop: Replacing the CMOS battery

I use my Dell XPS 13 9360 on a daily basis since early 2017 and never regretted the investment. But over the years, the battery has degraded and in the end - two weeks ago - my laptop started to behave unexpectedly: When I shut it off, the power indicator went off, but after about 4-5 more seconds it turned back on and my laptop started as if the power button was pressed. The only way to shut it down permanently was to press the power button for some more seconds and thus causing a force-shutdown.

At first, I was not sure why that happened and I suspected a hardware failure or some misconfiguration and even a buggy firmware update. But I realized quickly that some of the TLS certificates were not valid (yet) when I browsed the web. … and noticed that the clock was reset to some earlier date. It was clear to me: The CMOS battery was not able to keep the RTC (real time clock) running correctly. And that was probably also the cause of the reboot loops.

As I needed to open the case to replace the CMOS battery, I used the opportunity and replaced my degraded main battery, too. For my XPS 13 9360 I chose the following components:

All in all replacing both batteries cost me about 80 €. I was thinking about getting an original Dell Battery, but those would have cost about double the price (and I’m quite sure you’re paying a big “brand extra” here ;-) )

The replacement process was pretty straight forward: After unscrewing the bottom of the laptop, a pair of speaker wires needed to be peeled off the main battery. The battery is held in place by 4 more screws. Don’t forget to unplug it by gently pulling its connector. In the second step, the CMOS battery at the right side of the battery can be removed. It’s not mounted anywhere to the case and is just connected to the motherboard via a tiny plug, which can be pulled off easily. Before pulling the CMOS battery plug, try to memorize the polarity of the cables.

When re-attaching the CMOS battery, make sure the cables are in the correct order. Now the new main battery can be put in place. Plug it first, and then screw it back into its mounting position. In my case the manufacturing tolerances were not perfect and I needed to give the battery a tiny stretch to make it fit onto the mounting bolts. After making sure all connectors are in place, I re-attached the aluminum bottom plate of the laptop and powered it on.

It took about 2-3 reboots for the laptop to re-calibrate and initialize, before the operating system finally started. So don’t be worried if it takes about half a minute for the laptop to start up as usual.

When I was sure the battery and all the laptop’s features worked fine, I discharged the battery completely by playing a 4k YouTube video. After that I re-charged it to 100%. This process re-calibrates the battery statistics and ensures the correct display of the battery status.

As for the CMOS battery the whole operation was a success: The boot loop did not occur anymore and the real time clock was working perfectly. Regarding the main battery: It’s still too early to recommend this exact model, but my first impression is good. I’m back to ~ 8 hours of runtime at easy workloads.