My battery charges but when i let it charge for a

THe battery had probably been use to it's limit. With laptop batteries they only have a limited life span. A certain numbe rof charges. The best thing to do is when you have the laptop plugged into the wall power source, remove the battery. As with all rechargable batteries, it is not recommended to recharge them when they are half drained. Recharging them all the time kills the lifespan. Go on ebay and purchase another battrery. You can find one for under $30.