It works , Leave the 9v battery or 12 v power on for no more than 30 secs , You should see the thin horizontal wire glow faint red ,
although i have stuffed one doing this , the thin wire inside the display melted and broke, display glass RS now .
You will be surprised how much brighter they become .
 A 9v battery works okay on the small displays
you need 12v on the larger displays , good luck ...