Inspiron 600m battery issues

I have an Inspiron 600m that is having battery troubles. Basically, the battery light blinks red-red-red-green whenever the battery is plugged in. According to the computer the battery is 100% charged and it seems to get decent battery life for how old it is. I really don't understand why the red light keeps blinking though. Dell replaced the motherboard and AC adapter but the same problem keeps happening. It happens with both of the batteries that I have for this system. Unfortunately I don't have another Inspiron 600m to test the batteries in. It just seems like something needs to be reset. Dell said I need a new battery but I really don't want to spend $100 on one because this system is so old. Is there anything I can do?

I left the battery out of the system over the weekend. I plugged it back in. Voila! Problem solved.