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.

Imminent Vengeance wrote:
>
> 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.