radio display problem

[efrain88]

so i installed some 6x9 rear speakers today, i disconnected the negative battery terminal before i started working. so when i was finished i go and connect it again, but now when i turn off my car the radio display stays on. i know it probably isint enough power to drain my battery and i dont really want to take it to nissan because my warranty is long gone. has this happened to any one before?