This is a tricky situation I'm in. I have this already fifteen-year-old laptop, a 13" mid-2010 MacBook Pro. It works surprisingly well with the latest Ventura version, macos13.7.8. But, the battery isn't recognized; settings aren't even displayed.

Here's how the update went for more context:

Pre-Update

I booted up the MBP running Sierra on its 128GB SSD. It would only turn on when plugged to a wall and the battery showed the "X" icon instead of any charge, capacity or state info. Every now and then, the Mac would detect this as a malfunction and limit the CPU clock while blasting the fans at top speed. Suspecting a battery malfunction I unplugged the battery (which wasn't swollen, by the way). This isn't a new problem, the Mac's been like this for a while. After unplugging, more often than not, the mac wouldn't suspect the malfunction and wouldn't downclock the CPU.

Update

I installed a 480GB SSD into the mac, replacing the old 128GB one. Through a thumbstick and using an USB 2.0 hub for mouse and keyboard compatibility (the old hardware selects USB 1.1 for mice and keyboards, go figure), I installed Ventura with the battery still UNPLUGGED.

Post-Update

After finally booting up and installing all the much needed patches, the Mac obviously didn't detect a battery. None was plugged in. The seemingly random downclocking was still happening though, so I suppose it figured something wasn't right. I bought a new battery, which arrived yesterday, and plugged it in. To my disbelief, it wasn't recognized. The Mac didn't even try.

The charger always shows a green light, no matter what, and the battery status is always at 100% in Preferences. No battery icon is displayed, nor is it in the Control Centre tab under Preferences. System Information also says no battery is plugged.

Obviously I tried resetting SMC and PRAM, running First Aid, even checking for more OCLP patches. I also tried unplugging the battery, turning it on, shutting it down, plugging the battery, and powering it back on again, but it didn't work.

Now, the real kicker. Putting the old Sierra SSD back in, the new battery WASN'T recognized either. Too many questions.

Is the power board defective?
Is a patch missing on OCLP because I installed Ventura with no battery plugged in?
Do I need to reprogram the battery?

I'll keep on searching, but any help would be much appreciated.