This is what I bought
https://www.24mx.ie/ctek-mxs-10-battery-charger/56-708 I paid a lot less than that though, it was only 119 delivered on black friday.
I tried it on a few batteries and it seems to have done a good job. small example but our ride on is a terribly abused machine, it lives outdoors all year round and has no cover on the battery which must be 5 years old.
A month ago herself took a notion to cut the lawns but not a kick out of it, it was completely flat so I took it off and charged it, let it run through the full cycle (it has about 7 stages if you're patient) but by then something had come up and the mower wasnt started.
Put the battery in yesterday and it fired better than it would have at any point last year, and it hasnt been run in 3 months probably.
A small test, but I was impressed all the same.