my DS lite turns itself off even when fully charged?

Alhtough my DS liteis fully charged it keeps cutting out at regular intervals and i have to turn it back on again, it's doing my head in.

Anyone have any idea what the problem could be?

other than the amber charge light going out while plugged in, there is no way to tell if your DS Lite is "fully charged". In other words, if you are going by the battery indicator at the home screen, that means JACK.

One more thing. Before your DS shuts off. Is there a red light that comes on?

12 bucks us. Call Nintendo UK. They should be able to hook you up. Heck maybe they could examine the unit and repair it for free. Depends upon what you say. Have no idea how outstanding the UK Nintendo repair people are in comparison to the states.

Seriously you bought second hand quite often scum will offload broken stuff to a second hand shop that won't examine the merchandise.

yeah id go with a new battery. and dont buy an offbrand battery on ebay for 5 bucks.