Also, while you have it open (in fact, go and open it just to do this!), replace the internal SD card; they have a tendency to fail; my ereader had been getting very annoying with lag and random reboots until I did this, now runs like a dream. You'll need to copy your old sd card across or find an image somewhere (they exist on some forums) if it's too far gone (I got the bulk of my using DD rescue but there was a _lot_ of errors)
Like all Li-Ion batteries have nominal voltage about 3.6V-3.7V, and full charge at about 4.25V, depending on how risky you are today (yes, there are some minor variations in rated voltages, but not like 10x). Just because chemistry. For lower current (heat losses) you just connect the cells in series, so you got multiplies 2x, 3x, ... of the same voltages (but never fractional, like 1.5x). They typically have more wires to balance the charges between the cells (so the total wires count is #cells+1).
There are also "protected" batteries, which means there's an electronic chip that protects battery from over/under charging, but authors' doesn't seem to have that. It's just a regular unprotected 1-cell Li-Ion cell, and the device provides the protection.
That means author could as well connect to any battery of 3.5V -- 4.2V, not going through the hoops of looking for their particular reader, as long as it's thin enough to fit. Smaller batteries would just have less charge.
PS: I would double-check it's really unprotected tho.
Ereaders tend to be fairly unique. If my Kobo Forma dies, there's no other Kobo I can replace it with (in terms of size). I don't want to change brands and deal with yet another OS.
Some of the Kobo also support audio books. All of them have microUSB or USB-C to sync, some got Wi-Fi or Bluetooth as well. Mine even has a mic for some reason.
There's a plethora of hacks for devices like the Kobo (reMarkable is another one). For example, see [4]
Self hosted in Docker, I browse to the book I want, add it to a ‘shelf’ that is synchronised. then on the Kobo I press sync. It downloads.
I used a guide that was something like this:
https://jccpalmer.com/posts/setting-up-kobo-sync-with-calibr...
What’s your solution? A whole new e-reader with a model you don’t like?