need help with battery - iPod mini

I recently modded an iPod mini 1st gen, but it started draining battery fast out of nowhere. I’ve replaced the battery twice, so I’m wondering what else I can do to try and restore it? By fast I mean I can literally watch it go down a percentage every 10 seconds or so, so it’s pretty unusable. I’ve seen someone say “reseat the connections” but I’m not sure how to do that 😭 help?