Ds lite charging lite comes on but when i press power button nothing happens
Are you leaving the DS charge until the light comes off? Remember that there are two likes too, one for charging and one for power. If you're just charging for some random period of time (lets say... One hour) then your Battery isn't going to be fully charged. The best way to ensure that your DS Lite is charged is to leave it charge until the charge light turns off. You can play your DS Lite while you are charging (I do it all the time), but it just means that you're just running off of the outlet.
A good test is to charge it fully (until the charge light comes off), unplug the charger cord (Make sure it's secured tightly to your DS while charging), then play for a little bit, your light should be a normal color (green).
If you cannot even play by using the outlet, then you need to
find a charger cord that actually works (You may need to send in the charger for replacement). If the same thing happens with 2 different batteries (assuming that you have two official Nintendo batteries).
TIP: Also run your fingers across the Charger cord. You're going to get a slight friction burn from the rubber, but you're going to get all of the kinks out of the wire in the cord. My charger cord had a similar problem (did not charge all the way, only charged until I moved the DS) but when I ran my fingers across it (pinching) it worked again.
Also check the pins in both charger cords, charging will not work if one pin is missing, nor if any are bent.