Battery and charging issue

I did a battery replacement on 6 iPod touch 6th gens. All devices power on after replacement but all the batteries still lose battery life within minutes. Also when you plug them in to charge it indicates charging but even after leaving each one charged for an hour or more the battery percentage does not go up whatsoever even if you hard reset the iPod. Tested each battery and all of them were around 3.8v mark. iTunes does recognize the iPods when I plug them into my laptop. The batteries I used were of a lesser expensive type as opposed to say the ifixit batteries which I just purchased to try because I think these would be of a better quality. Has anyone had this issue? I’m guessing since the charger port works and it recognizes iTunes that the charging port would not be suspect. Any insight would greatly be appreciated.