Replacing Sony reader PRS-500 battery

I inherited an old Sony e-ink reader Sony PRS-500. 

I'm unsure of how old this thing is, but I would argue about 6 or 7 years. Most of that time it was lying around unused and forgotten, but was actively used in the first couple of years after purchase.

Stock battery: LIS1356HNPAQ (SY6), 850mAh, 3.7V;

After 7 the battery deteriorated, and I could only go through 100-150 pages before it shut down. 

Moreover, it was missing the original charger, but that issue was resolved swiftly and easily. I simply had to find appropriate center-positive plug, and solder it with red and black wire of a USB-plug. The original charger was supposed to be 5.2V, USB's voltage is 5.0V, which is not much of difference.

Now, let's move on to the battery replacement. There are two options I could find:

1) 750mAh 1-756-769-11, LIS1382(J), 8704A41918 -> Ebay
2) 850mAh Battery For LIS1356HNPA, 1-756-608-21, 5Y30A1697 -> Ebay

The first one was a bit cheaper (12usd vs 19usd), paying 7$ for just 100mah seemed a bit inappropriate. Besides, a fully-charged battery is enough to flip thousands of pages, it's not like I would notice the difference in 100mah!

It is easy to disassemble the reader, take out the memory card, unscrew all the screws you can find, and remove both side panels. After that, unscrew everything under those panels. The back panel should come off after that very easily. 

Replaced PRS-500 battery, next to the original one

Piece of cake! 12$, and the reader is good as new!