Battery for Kindle PaperWhite EY21

As it happened, a battery for an e-reader from the well-known Kindle brand ended up in my hands, and I decided to test it. I was especially interested because not only had I bought it on AliExpress, but it had also been sitting in a box for a couple of years.

To keep up with new posts on the blog, I recommend following me on Instagram, where I'll post notifications about every new topic and might also write about something interesting: link to my account

As mentioned in the introduction, I bought the battery a couple of years ago as a spare for a Kindle e-reader. After that, I simply tossed it in a desk drawer, where it stayed until recently.
Unfortunately, the original link has expired, so I had to find the closest match.
I also came across a few other versions along the way. I can't say which ones are better or worse; I only tested the one featured in this review.

I also came across similar batteries with slightly different markings. I wouldn't buy those; they look like counterfeits.


The package also included adhesive strips for replacing the battery.


The dimensions are standard and match those of the original battery. In addition to the power contacts, the connector also carries a digital interface from the built-in controller.


The battery was discharged so far that its controller had shut it down due to low voltage. The initial cycle, like the ones that followed, was run using an EBC-A20 battery tester, but before starting the test I had to "jump-start" the battery from a bench power supply.
Below is the first charge-discharge cycle; the parameters are shown on the screen.

By the way, a friend said he'd later seen reviews from other people who had also received a completely discharged battery.


A full charge at 0.5C (0.71 A) took just over two hours. In my opinion, that's excellent for a battery like this.


I tested discharge at four rates: 0.2, 0.5, 1, and 1.5C. I decided not to push it any harder, partly because the battery isn't mine and, more importantly, because there was no point.
Surprisingly for a battery from AliExpress, it delivered its rated capacity not only at 0.2C, but also at 0.5C.


The temperature rise at 1 and 1.5C looks excellent to me.


Measuring internal resistance. Keep in mind that this is the combined resistance of the cell and the protection transistors.
1, 2. Initially, the meter showed random readings because the protection circuit was blocking the output.
3. After the test, with the battery fully charged, the total resistance was about 0.1 Ω. That's a bit high, and it's also noticeable on the discharge graph, but it's perfectly fine for an e-reader with its low current draw.


I'll keep the conclusions brief: the battery meets its specifications and is recommended for use.

If you've already bought one of these batteries, I'd be glad to read your reviews. That's all for now; I hope you found this useful.

Stay strong, friends. I believe Ukraine will win.