In this post (in German), an original Olympus battery and one from Patona (and a no-brand one) were dissected. The OEM battery had a much better design than either third-party battery, with solid casing, nice electronics, and a bit of margin for swelling.
Patona installed the best cells. A decent electronics like Olympus and they would be absolutely first choice - even for the price of an original battery. Despite the defective battery, Olympus delivered the best manufacturing quality. Everything is in its place, everything is as it should be and the whole thing is safe. You can see it: even leaked electrolyte cannot inflate or set fire to the battery case. This is because Olympus realized the gluing with foam rubber strips on the edge, not in the middle. And that’s why the bags can inflate up to a millimeter on both sides without anything happening.
[…] The Patona can be considered as an emergency replacement if you don’t use it more than once a month. Then you will also last for the life of the camera. Because the Patonas are actually killed by the charging electronics. As long as you don’t [charge] them, they are great….
On the electronics found in the two third-party batteries:
After all, the cells have a center tap, which is led to the board on B1. Unfortunately, it goes to a 470 ohm resistor and not to a charging electronics, which explains the short lifespan of the batteries. Again there is no load balancing. It was already clear that there was no thermal resistance.