BLACK DECKER 9045 TYPE 3 4.8V BATTERY charger

You need to post MORE information like what is it doing or not doing and how you use this charger then we can eliminate operator trouble and focus on the charger.

What I do know is that some NiCd 12V Black decker batteries that look similar to the dewalt ones they are charged by the dewalt charger.
But there are 12V Nicd black and decker batteries that they can not be charged due to an extra plastic edge that does not allow to be charged by the dewalt charger.
Now if you do have the dewalt lithium 36V charger and if the black and decker battery is a 36V lithium one and can not be charged due to a plastic edge then I would recommend to risk to destroy the plastic edge in order the black and decker battery to be charged.

You need a volt meter, They are cheap and it will come in handy down the road. The volt meter will tell you if your charger is the problem or the battery has went to battery heaven.

With a multimeter set it to 12 volt dc and place the leads on the two parts that would be touching the battery. If you see voltage then it is a bad battery.

-David

check voltage on prongs of charger your transformer my have died

Nope. It takes a different charger.
Farmerbear at FixYa.com

You need a new charger. If batteries where bad charger would still light.

The replacement part is :
Part Number: 90500901
Description: CHARGER
Status: Active

List Price: $6.69
from http://www.dewaltservicenet.com/Products/PartDetails.aspx?partid=277868

change batteries, your charger should indicate wheather you battery is good or noot on the pause inbetween blinks.

My charger has a fuse located on the circuit board inside the unit....when mine stopped working, it was the fuse...replaced it and it is working fine for one battery, the other blows the fuse every time....bad battery.