36V 19Ah downtube ebike battery from Grin Technologies (ebikes.ca).
This is from Grin Technologies, a Canadian company that was recommended to me by Blue Heron Bikes. They have a great reputation for sourcing and testing all the batteries they sell. It comes with documentation of its testing showing that it works as advertised.
The specific item is:
https://ebikes.ca/b3620-li-dt.html
I bought this last month as a replacement for my big, very heavy front-bucket cargo bike, but turns out its the wrong voltage for its motor. Now I can't return it because apparently it's not legal for individuals to ship lithium-ion batteries this size.
It is brand new. I used it only on two 15 minute test rides.
I paid $925 for this: $555 + $170 shipping + $200 tariff