Most of the Ebike batteries have a low C value.
Not ment to put out a lot of ampères in 1 go, like we need for our machines.

Also, in a decent ebike battery box there is an electronics board that makes sure the cells are balanced when charging.
That board too isn't ment for any decent ampére handling.

In the very cheap knock offs, that board is lacking, and the cells are just charged in series, making sure the pack will fail inside a few dozen charge cycles.