Did I just shorten my car's battery life?

When I left work to go home yesterday, I noticed that my '93 Accord's dome
light was on before I even opened the door. After I got in and closed the
door, the light was still on. I checked the switch on the light itself, and
it was in the middle position (light comes on only when a door is open).

Now fearing that my battery may have been drained, I turned the ignition to
"on". After the "lamp test" concluded, the door ajar indicators showed that
one of the passenger doors was open. Turns out that, unbeknownst to me, my
passenger did not close the door tightly when we arrived at work 9 hours
earlier.

As it turned out, the car started with no problem at that time, and today it
was also fine. Which brings me to my question. Is it possible that I (or
should I say, my passenger) still may have shortened the battery's life by
having the dome light continuously on for 9 hours without the car running?
Or is the dome light less taxing on the battery than, say, the headlights
and it will be OK?

The battery is an almost 4-year old Sears DieHard, if that matters.

Thanks in advance for any answers you can provide.

 

You definately shortened the battery life by about
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0000000000001 sec.




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Do not write below this line. Reserved for me.

 

Dealers and parts sales definitely love paranoid people.....

 

I wouldn't worry about it.

 

The dome light in your Accord is 10 watts. Your headlights (low beams)
are 55 watts each, plus 7 watts for each tail light. So leaving your
headlights on is a 124 watt problem, the dome light is a 10 watt
problem.

9 hours of dome light comes to something like 7 amp hours, or order of
magnitude 1/10 of your battery capacity, hardly a deep discharge!

So, although I wouldn't make a habit of leaving the dome light on, you
did not cause any measurable damage to the battery.

 

IIRC, it's running the battery all the way down and then jumpstarting the car
that will have the most adverse effect.

My first two batteries on my 1991 Civic lasted 4.5 years each. Each had a few
jumpstarts and rolling starts (manual transmission trick). Still, 4.5 years is
not at all bad.

To spare the alternator undue stress, it's best not to wait until the battery
completely dies.

Maybe at about the 4.5 year point you'll want to keep an eye peeled for places
that will do a free battery check. Autozone?

 

Is it possible that I (or

No. The drain is minimal. It would eventually kill the battery,
especially if it isn't in good shape. (This sometimes drive people
crazy until they realize that the bulb in the trunk is on all the time
due to a faulty switch.)

If the car still started, I'd say you proved that the battery is still
healthy.

Several years ago, my daughter left the car headlights on until the
battery was cold, stone, dead. I was sure that the battery (a
semi-cheapie Champion) was screwed. But, after a jump start the
battery lasted fine for another 3 years until the car was traded in.

Further proof: I walk my dog late at night. I frequently see
people's car interiors lit up by the dome light. Obviously they're on
all night but the next morning the car is gone....

JM

 

Thanks to those of you who provided informative answers.