If your Nintendo ds lite won't turn on, when you switch it on, you can try to fix it, by applying the following solution below:
1)Make sure your Nintendo ds charger is working. If you have a spare working Nintendo ds console, that has a working battery, use the charger to charge that console. If the charger works on that console, it shows that you will need a replacement battery pack, for your other Nintendo ds that won't turn on. It it doesn't charge the spare working console up, your charger is broken, so you will have to replace it.
2)Test the battery in a spare working Nintendo ds console, if it doesn't work, replace the battery, with a original battery.
3)If replacing the battery didn't work, then check the charging slot and power on switch. If you suspect they are damaged, then replace them.
4)It is probably a blow fuse on the circuit board, so watch the video below because it shows you full instructions on how to bypass the fuse using a conductive pen, if you don't have a soldering iron.