Cordless Weed wacker charger question?

i have a Toro Cordless Trimmer. The Battery is a 12v7.2 AH. the charger that was included (12vDC9.5W)has been spliced and does not illuminate the red light, on the weed wacker, when plugged in. I am wondering if i could use a different charger (12VDC500mA)? What should i do? I respliced the original charger and it still does not work.