The switches in the dash aren't connected to anything but computers...so whatever killed your battery is going to continue to drain it until there is enough power to boot the computer, read the new position of the switch, and change the state.

In this case, the Range Rover Sport lights were left on. They were on manual instead of automatic because I was driving in overcast skies with snow but it wasn't dark enough to trigger the auto-headlights. Since 99.99% of the time they're on auto, I forgot to switch them off.

Now the battery is dead. I turned the switch to "OFF" and plugged the charger up...but it didn't turn the lights, that killed the battery, off. The LEDs are on and I can hear the xenon ballast trying to fire without enough power. Come to find out that the car won't turn the lights off until there is enough power for the ECU that controls dash switches to read the new position of the headlight switch and turn them off...but the drain from the lights slows the charge...and the tug-of-war continues.

Long story short to make any progress charging it I had to disconnect the terminals to keep it from draining the charging battery.

Oh bright and glorious automotive future...

On a side note, the engine bay on a Range Rover Sport is so tight, they don't even bother putting retention/hinge tabs on a lot of plastic covers, it's just wedged in the edge of the engine bay on one end with a clip on the other.

Advertisement

(Update) Expected jokes about my name...did not leave disappointed.