Споменах dtypes
изрично и ми свърши работа за postgres.
//sample code
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.dialects import postgresql
df.to_sql('mytable',pgConn, if_exists='append', index=False, dtype={'datetime': sqlalchemy.TIMESTAMP(), 'cur_c':postgresql.ARRAY(sqlalchemy.types.REAL),
'volt_c':postgresql.ARRAY(sqlalchemy.types.REAL)
})