Yes. The suggested 30 minutes is based on a single observed case: it took 26 minutes for the lightning symbol to appear. All my other conquest batteries responded a lot faster: the lightning charge symbol appeared within a few minutes. But this last recent one was worth the wait. After I charged it, it runs my Pismo for about 4 hours. So insert each unknown battery and give it at least 30 minutes, maybe an hour, to see if the charging symbol ever appears before you toss the battery in the recycling bin.