After doing some more reading on the forum I came across lots more info.
A quote from JSWolf:
Originally Posted by JSWolf
You have just been lucky so far. The best thing to do is to toss this charger and get a true PSP charger. Just because the pug fits and it seems to work, doesn't mean it actually does. If you use an incorrect charger, you could be damaging the unit or causing a problem with the battery.
I have decide to return the so called PSP charger I purchased and have found a place I can buy a REAL PSP charger...tomorrow. It is 5.2v 2000 ma.
An informative thread here:
https://www.mobileread.com/forums/showthread.php?t=26915
I don't think I did that right ...