MY PS2!!!!!!! i need help....my ps2 Slim wont stay green light for more then 1sec.?

Now to mention... my dad found this ps2 (slim) in an apartment so i tested it with my psp charger it stays red light but wont stay on green for more then 1 second. I am thinking maybe because it does not have enough power to keep it running?? now iv'e tryed this before with a regular version ps2 and all i had to do it take off the adapter on my psp charger n plug it in. but i do not recall the dcV on the back with i think means the actual power the power cord is putting out. now my psp charger is a 5v ac adapter and on the ps2 (slim) it says dc.V8.5. Is my problem that the psp charger is not giving enough power to the ps2(slim)? if anyone has the knowledge please comment. thanks