what certification is required to sell electronic products?

[bson]

I said lipo, but didn't really mean any specific chemistry. Though I do want to put the safest battery in it (single sell, 1000-2000mAh) just for the peace of mind.

Use LFP then.

[Smokey]

Note that there are different rules around shipping batteries by themselves vs shipping a product that contains a battery.  Also country of origin and destination matter as well.

I had a box of 1000 individually packaged 500mAh Li-Poly batteries shipped to my door from China with no questions asked and no extra handling.  But when I tried to ship 3 of those batteries to the Netherlands for testing and characterization I got rejected by UPS, FedEx, and the USPS.  Only DHL would accept that shipment.  None of the restrictions would have been in play if I had just shipped the batteries as part of a product.

[strawberry]

same when handling returns. incident happened when someone bought kids toy with removable battery and same service rejected sending it back because it is lithium
I suspect they earn cents from UPS etc and dont want to dig into legal stuff.
I think, they know how to design products so that they get less returns