Measured Decline of a Laptop Li-Ion

Back during the pandemic, I treated myself to a brand new Dell XPS 15 9500 laptop. It has 6 cores, 16GB of RAM, and an NVIDIA GTX 1650Ti (mobile). Even today it still holds up as a "good" machine. I like it because it has a rock solid aluminium chassis, comfortable keyboard, and the screen is an extremely low-bezel 16:10 rather than 16:9. To their credit, the Dell support bloatware is pretty good too, with regular driver updates even 6 years after purchase.

Last year, after trying to run a pygame of all things, the display broke. It was irritating; I'd just been trying to get it to run a basic game and yet it ended up burning out (I presume?) something in the onboard display, which meant I could only use it with external monitors. At the time, it wasn't worth replacing the whole laptop, so I forked out several hundred pounds for a new display assembly. It arrived, I installed it (a relatively painless experience thanks to several online tutorials), and that was that.

This year, I noticed markedly reduced battery performance. It gets hot, and lasts barely any time (not even an hour!) on a full charge. Thanks to the state of the electronics industry right now, it once again wasn't worth forking out for a new machine (have you seen the RAM prices right now?). So, I begrudgingly started assessing the problem. A good start is Windows' built-in battery report, which you can generate with:

This command asks Windows to write a HTML battery report with details like the runtime after each charging, as well as the full-charge capacity. With a little tweaking to make it output XML, and a short while spent with the ElementTree and matplotlib docs (and a healthy dose of help from ChatGPT to make the whole process more bearable) I was able to plot my battery's health over time.

As you can see, something happened in mid-2024 which made my battery start a slow and inevitable decline. The full-charge capacity has dropped pretty much linearly ever since; it's a wonder it's taken until now for me to notice the problem. As HWiNFO64 tells me, my battery's "wear level" is 69.6% (nice). Unfortunately that means full-charge capacity is now only 30% of what it is supposed to be. That would, in fact, explain the poor performance...

Happily, replacements aren't too expensive. It's a 6-cell, Li-ion, 86-Wh, M59JH07 available as a spare part direct from Dell (apparently the third-party ones are cheaper, but don't fit properly and can prevent the trackpad working correctly). One was delivered earlier today as I write this, and should be installed by this time next week. In many ways this whole article is just a sorrowful lament at the state of the tech industry, and at the fact that battery technology is so unforgiving after just 2-3 years of use. My heart aches for the day I can buy a laptop with a Lithium-Sulphur battery which gets charged once a week and lasts 7 years' of charging cycles.