Ok, i have 2 classic Pleo, don't have any battery, box, charger, manual or any other thing, only have the dinos

Since I have no battery, I have plugged them directly into a transformer with 7.2v

When I hit the power button at 8/10 seconds they grunt, (no movement) and remain silent until another 8/10 seconds pass and they make the same grunt.
https://youtu.be/1zpGHj1rWWII can't get the youtube video to come out.
As I read, that growl does when you feel the battery too hot, correct?
what should I do? Buy a battery? Make a trick? Do I use paperweights?
See if you can guide me because I'm looking forward to reviving both of you
