I should say, if you really just want a ~10 amp charger for a 24 volt battery bank... just get yourself a decent 24 volt battery charger.
This is $50. If you really don't wanna go with a quality purpose built solution, just get something designed to do the quick and dirty task you want to do. :P
Inefficiency.
It'll unbalance them.
It costs more than just one 24 volt battery charger.