It does exactly what it promises to do. It can be a bit temperature sensitive as I live in a very cold area, but as the charging itself warms the battery slightly and it takes a few seconds to run all its own diagnostics before telling me it is too cold, taking the battery out and replacing again it a couple of times gets it started fine. It has no other problems.
As I have several power tools which use various amp batteries, I can now keep the tools going, by charging 2 batteries at a time. So much easier an more efficient.
Well done for producing such a product!