I recently purchased a used 'very good' condition battery for my mavic pro 2 drone from them. Within 10 charges it began to swell so much it cracked the plastic casing and became faulty and unusable with the drone. It actually created a huge safety risk that could have resulted in the battery pushing itself out of the drone mid flight and causing a total catastrophic failure and complete loss of my drone which I use for professional videography work. MPB refused to exchange the item or offer a refund and said batteries are not covered under any warranty! They offered me 10% of another battery but were not able to guarantee that the same would not happen again and I'd be out if pocket for 2 drone batteries or worse- completely lose my drone due to a mid-flight failure.
My advice would be not to use MPB for anything battery related - especially anything related to drone equipment.
If anyone would like more info happy to give it and provide pictures.