hello,
I heard that Ni-Mh battery could cause damage to an old speedlite 199A ?
Did you hear something like that before ? what is your experience with this matérial ? did you try this mariage ?

Thank !

There is no reason your 199A flash could not use Ni-Mh batteries. They will charge the capicitor a little faster when they are fully charged but not last as long as Alkalines or Lithiums (very expensive for flash use). Keep in mind NiMh battiers will go dead all b themselves and should be charged up just before use.