Due to the many questions about some of the protection circuits in some of the batteries I am selling (mfg. by Evva-Tech), I decided that a teardown was in order. Although it pained me to do this to two brand new batteries, I had to see what we had inside of these cells. I decided to do a comparison to the admittedly similar looking Keeppower. I have no way of doing any fine testing of these circuits the way that HKJ does, so this is more of a visual comparison.
The two cells to be torn down
Slicing it open
Rear end - Evva left, KP right. The material appears to be similar, if not identical.
Button tops
With wrappers removed. Note that the Evva circuit has a larger OD.
First look at the KP circuit. Looks like AO8814 MOSFET with Seiko S-8261 IC. This comes in various configurations: datasheet.
Looks like this one has a “G2JA” which isn’t found in the datasheet.
First look at the Evva circuit. It looks like the same major components except that there are (3) MOSFETs vs. (2).
Big view of the two together. Looks like they even share the same value resistors.
While I do not have any quantitative evidence to prove it at this point, the Evva looks like a good protection circuit that uses a Seiko IC as specified as well as good MOSFETs. The KP circuit is obviously well made and is held in high regard and is often said to be the “gold standard” of protected 18650s. I am not sure how much difference the third MOSFET makes, if any at all. It could potentially lower resistance in high drain scenarios but I am not sure of that.