The man is accused of injecting patients aged under 16 at the hospital's child and adolescent unit with the drug paraldehyde as punishment, between 1974 and 1977.
Court documents say he did so for reasons including boys running away; calling him a bastard; "being smart"; and because a boy was "enjoying himself too much, laughing and having jokes with friends".
Six alleged victims are named in court documents, while another charge refers to an unidentified child.
The man, who lives in the central North Island, walked into the back of the court with the aid of crutches.
Winter requested strict orders about the court process because the man turns 90 next year.
The ill-treatment charges have a maximum penalty of 10 years' jail.
The man is on bail. His case will be called for an administrative hearing in March, but the man may not have to attend.
Last week, police announced they had charged one person after their latest investigation into allegations of ill-treatment at Lake Alice.
They said although there was enough evidence to charge the unit's head psychiatrist, Dr Selwyn Leeks, he was medically unfit to trial, as was another former staff member.
Leeks, 92, lives in Australia and suffers from dementia and cancer.
Previous police investigations in 1977-78 and from 2002-2010 resulted in no one being charged.
At the Royal Commission of Inquiry into Abuse in State Care this year, police apologised for shortcomings in the 2002-10 investigation.
