fasttech and Focalecig sell Velocity clones for $8-9, and that's probably what the ebay one is. I have one from Focal and its fine. So go ahead and get that if you want it. I doubt it has any major issues. I've been using mine for months.
With batteries, you always need to be careful. I wouldn't buy Sonys on ebay as there's too many counterfeits, but Samsungs or LGs are probably ok if the seller has very good feedback.
With batteries, you always need to be careful. I wouldn't buy Sonys on ebay as there's too many counterfeits, but Samsungs or LGs are probably ok if the seller has very good feedback.