Hacking EZ Flash IV (black) battery drain

[romanaOne]

I got one of the new(ish) EZ Flash IVs recently and there is something wrong: it came with a cr2032 stuffed in it and the case was bulging so much it wouldn't easily fit in a GBA SP. The battery was just wedged in there, the contacts unsoldered.

I put a smaller Energizer CR2016 (specs say 100 mAh) battery in there and it was drained to 0 V in a couple of weeks. The games in NOR flash were also corrupted (Names turned Chinese and they would crash on launch) and replacing the the battery did not fix it. Now it was firmly in place, sandwiched between enough kapton tape to keep it snugly in there so I don't see how it could have been shorted.

I've got a CR2020 (115 mAh) in there now. I'm not expecting great things. Seems to be working fine; reflashed games to NOR and tested that they save. Maybe the person who sold it to me was aware of the defect and that is why they'd stuffed such a big battery in it....to give them time to get away. Is this short battery life common with the new ez flash IV?

Sounds like this has happened before:
https://gbatemp.net/threads/ez-flash-iv-battery-short-draining-too-fast.369228/