1991 Mercury Topaz mileage: 125,000. I was on the highway today, with my window defroster (front and rear) on, my stereo, which employs a 300-watt amp, my headlights and we were stuck in a traffic jam. After about an hour and a half of idle sitting, my car died and the battery appeared to be dead. I just had the alternator changed last year and when that was dying my battery light popped on, but that didn't happen this time. When I got the car back home, I just jumped it and it started fine. What could be the problem?
You may or may not be having a problem with your car. From what you have described, you may have just drained your battery down. Think of your battery as a bank account with a limited amount of money in it. As you drive your car at highway speeds, you are putting money into the bank (charging the battery), as your car sits and idles with your window defroster, stereo and headlights on, you are withdrawing money from the bank. Eventually you will run out of money and the car will die. The battery may be weak in your car or it may be not have sufficient capacity. The more expensive batteries with higher amp ratings normally have more money in the bank.