Thinkpad T420 suddenly apparently rejecting battery, unsure whether battery or laptop causes the issue

[OrganicBrian]

Hello, I have a Thinkpad T420 (Thinkpad Product ID 4236VUD, Serial Number PB-FTMG7, running Linux Mint 20.3 xfce 64-bit) that has been using a Duracell Ultra COM12647A battery (branded for Batteries Plus Bulbs, I bought it using their website) since Jul 2019. The battery performance has been fine, as far as charge/discharge times and it hasn't been getting unusually hot or showing any weird behavior on the battery itself.

Suddenly around Dec 11th the battery does not charge, and this appears to be due to the BIOS deciding not to charge it. When in Linux Mint while plugged in, the battery indicator shows "Waiting to discharge" and the battery level doesn't increase. When plugged in but the power is off, sometimes it charges but usually it doesn't (most often it charges after removing battery and holding Power button to drain the board's power, then re-installing battery and plugging in power while laptop is off). On one occasion during boot, I was shown this error before the OS choice screen (so the error must have come from the board, not the OS): "This system does not support batteries that are not genuine Lenovo-made or authorized. The system will continue to boot, but may not charge unauthorized batteries, and provides no warranties for failures or damage arising out of their use. Press ESC key to continue."

I've been trying to find out whether this issue is caused by the battery or the laptop. The tech support for Lenovo, Duracell, and Batteries Plus Bulbs (Duracell does nothing but transfer me to them) haven't been any help. I remember seeing, in the Update Manager in Linux, a "firmware" or "Intel microcode" (something like that) update around the time this started happening. I wonder if an automatically-installed update can cause the T420 to now use a whitelist for batteries? Or, could the issue be caused by a battery going bad?

Another concern I'm trying to solve is that I'll eventually need a replacement battery regardless. The websites of Lenovo and Encompass have been out of stock of batteries for the T420 for years, or at least they are now and they were in summer 2019 when I last needed a battery. Those companies will give me no guidance about how I can avoid counterfeit/incompatible/inferior batteries. What is a good battery for this laptop? How is it known to be good (authorized, equivalent quality to original)? How can I avoid batteries marketed as compatible and of equivalent quality when they're not? The battery I use now has been great for me. The laptop still runs for about 3.5 hours per charge when using several apps and even almost that long while running video such as streaming entertainment. This battery however lacks the red "70++" logo which I think indicates an authorized replacement for Lenovo laptops of certain types (including T420) but the Lenovo site isn't informative about this from what I've seen when searching.

Could the battery's on-board controller have a pre-programmed number of charge cycles after which this problem is triggered? How could I find out whether the battery is causing this?

If the T420 is now using only whitelisted batteries, it seems important to find out which batteries are in the list and buy only one of those. I've been unable to find good info about this, though, usually the info I find about whitelisting batteries is in regard to newer models of Thinkpad. There are even articles and videos about hacking a Thinkpad's battery whitelist, but I haven't seen any in regard to T420. Probably, either a software update or a battery malfunction is causing this and if so I'm trying to find out which.

[RealBlackStuff]

There is no "whitelist" for batteries on the xx20 models.
That 'only' started on the xx30 models.
Try that battery in another T420 or borrow another battery from someone to find out where the problem is.

[dr_st]

Another concern I'm trying to solve is that I'll eventually need a replacement battery regardless. The websites of Lenovo and Encompass have been out of stock of batteries for the T420 for years, or at least they are now and they were in summer 2019 when I last needed a battery. Those companies will give me no guidance about how I can avoid counterfeit/incompatible/inferior batteries. What is a good battery for this laptop? How is it known to be good (authorized, equivalent quality to original)? How can I avoid batteries marketed as compatible and of equivalent quality when they're not? The battery I use now has been great for me. The laptop still runs for about 3.5 hours per charge when using several apps and even almost that long while running video such as streaming entertainment. This battery however lacks the red "70++" logo which I think indicates an authorized replacement for Lenovo laptops of certain types (including T420) but the Lenovo site isn't informative about this from what I've seen when searching.

I can't answer your other questions, but I will give a shot at this. Once the original manufacturer ceases production, the meaning of "counterfeit" gets moot. At some point, for every laptop, original, OEM, "authorized" batteries are no longer produced, and users have to choose between "new old stock" (which means original, but very old batteries) or "compatible" (produced by third party vendors). Since most such vendors are based in China, and it is hard to find any reliable information on them, one has to either trust their luck, or (hopefully) find retailers that work with third-party battery manufacturers and have experience in regards ti which can be trusted.

[OrganicBrian]

Once the original manufacturer ceases production, the meaning of "counterfeit" gets moot.

I meant that I'm trying to avoid buying a battery that (as a couple examples) has a "70++" logo which doesn't actually meet this standard, or buy a battery labeled as for example Duracell when it is in fact a cheaply-made copy that isn't associated with that company at all. I mean, a misrepresented battery which according to many reviews/articles are quite prolific right now.

[dr_st]

I meant that I'm trying to avoid buying a battery that (as a couple examples) has a "70++" logo which doesn't actually meet this standard, or buy a battery labeled as for example Duracell when it is in fact a cheaply-made copy that isn't associated with that company at all. I mean, a misrepresented battery which according to many reviews/articles are quite prolific right now.

This I can understand. If so, I would avoid anything that is coming out of China, and presented as "Brand new" genuine with a Lenovo label and number on it. These are definitely misrepresented.

I had come across a couple in the past - an 81+ for a T430s and a 61 for a T470/TP25. Both worked, but the fit and finish was poor. I didn't keep them around for long, because it bothered me.