battery life question and Roadside Asst. comment
 

95 e300d. The battery in the car now is a duralast purchased new in Jan., 2006. Yesterday, I left my primary headlights on for around 75 minutes. It wouldn't start. I've left my lights on before, not for that long, but an hour and 15 minutes doesn't seem long enough to prevent starting. Am I wrong? I checked voltage a couple of weeks ago and alternator is working and battery is strong.

So, sitting there in Charlottesville, 100 miles from home, I called MB roadside assistance. I got a call back after 5 minutes saying a tow truck was on the way. 1.5 hours later, a guy in a wrecker comes by, barely touches the jumper cables to the battery and it starts. Guy says MB Roadside covers the cost of the jump. I tipped him and drove home. Even though we waited a while, I was really surprised the jump was free. My insurance would have covered it anyway, but still it was cool.

IF you add up the wattage that the headlights & parking lights use..then subtract that from the battery's rating you can figure how long it will last.

Each headlight uses 45-55 watts.
Each parking bulb uses 10 watts, side markers & tag lamps as well.
2 headlights = 100 +- watts
8 parking lamps = 80+- watts
Almost 200 watts including the interior lighting....divided by 12V =16+ amps on a battery rated at 80-100 amps.

I would think a good battery would last 2 hrs at that rate before not having enough power to start the car!

Thanks a lot Doc. That's very helpful.

I THINK 3 YEARS IS ABOUT THE LIFE OF BATTERY
 

While you had him there I would have paid (tax and install free) for a new MB battery. I will trust a quality MB battery 4 years (maybe 5) in this hot climate, but 3 years for any other brand and 2 years for a battery in a new car. Optima is the only other battery I've had (not saying there aren't more, just haven't found them) that lasts 4 years of abuse in the South. The off brands may still be starting the car after 3 years, I just don't trust them after that amount of time....

My .02 cents FWIW.

John in San Antonio
(who hates dead batteries worse than running out of gas)

My car beeps at me if I leave the lights on. Very helpful!! It also doesn't like me to leave the key in! It also likes me to wear my seat belt! It is a very thoughtful car!

My New Favorite
 

Battery