Batteries on eBay and Amazon are a significant risk.
I will give you a metric to locate sellers who are certain to be "dishonest" about their batteries.
Go on both the sites and search for "Hailong 48v 30ah"
Write down the name of the sellers for all the listings that come up, and put them on your "do not buy from list".
Every product which comes up is certain to be a lie. The seller is either "looking the other way, or is intentionally dishonest".
Why? That would be a 13s6p battery using 21700 Panasonic batteries to achieve this. The problem is, A Hailong case cannot possibly hold that many cells.
Weight can be a giveaway. If the battery is 48v, with 21700 cells, and weights only 9.4 pounds.... it cannot possibly be more than 20 Ah of current.
That is the weight of JUST the battery, and not the mounting plate to attach the battery to the bike.