I have a 98 honda civic that has 150,000 miles on it and here recently the battery light will not go off. We replaced the battery and the alternator checks out that it is good. The cables to the battery are nice and tight but the battery light will not go off unless your foot is on the brake and the car is stopped. I was wondering what should a normal alternator be charging at. I think mine was charging at 17 volts or something like that. so could the alternator be over charging the battery. Also, there has been a rotten egg smell coming from the car at first we thought it was battery acid from the old battery but the smell is still there. I was wondering if the Catalytic Converter going bad would make it to have that smell.

 

17 volts is not good. You want no more than 15, more like 14.0 to 14.5. Replace the alternator. The battery will make that smell when overcharged because it contains sulfuric acid. Prolonged overcharging will burn up the battery.