This was the LifePo4 Battery I have:
eBay - Item#230827885844
I've gone over 70 miles on it and it's been through several good charge cycles and thus far it's holding up. At this point I would be willing to recommend him if your on a tight budget. It's possible they are "duct tape" batteries" But the ones this guy had had that black textured covering over them just as they appear in the "stock" photo he provides. The charger is working as advertised and is indeed a 6 amp charger (or close to it). I get about 13 miles out of a single charge with my 350 watt 36 volt mid drive motor. It's not currently set up for the pedals to work, so that range is if you do no pedaling at all. If you have a higher power system, I would recommend getting a bigger capacity battery though. I think 12ah is the minimum that a 350watt system should run on so a 450+ would need 15ah or more.
The only thing to look out for when reading this guy's specs on the battery is that he got the "rated discharge" current wrong. Clearly it is not 12ah since if that was the case the battery would have cut out the moment I tried to use the motor. So apparently this guy gets the capacity and max discharge rate confused. He does state that the discharge rate for this battery is 2C but I have no idea that that number means in the real world.
I'd recommend asking for express shipping if you buy from him. Like most China sellers, they will ship by sea mail if you don't elect for express. Expect 8+ weeks for delivery if you don't get express shipping. With that seller, it was an extra $87 on top of the $66 shipping to get it to the US in under 6 days. Though would have been faster if there wasn't a few communication mishaps.
You can probably find one sold in the USA, but even if the seller gets them from China, they will still charge an arm and a leg for it compared to the prices you get by getting them direct from China. I'm on a shoestring budget, so I didn't have much choice.