It depends on which lights and how long. If it was one of the smaller lights inside, most likely you will be fine. If you were to leave a light on with the car off, then it would be powered exclusively by the smaller 12v battery in the back of the car and not the traction battery. Depending upon how much charge you have in that battery will determine how long the light stays on. Think batteries in an always on flashlight. Eventually those cells will lose charge and the light will dim until it goes out.
Leaving something on in the car after it is off is no different in the hybrid than any other car. The motor is not powering any devices, just the 12v battery.
Of course that is only when the car is off.
When the car is on, that is a different story. It is my understanding if the car was on, the traction motor and ICE would power the equipment in the car such as the lights. The Traction motor would be on first until the traction battery goes low and the ICE would kick on to recharge the traction battery. That cycle would continue until you run out of gas and then there would be nothing to charge the traction battery and that would eventually go dim as well.
Either way, count yourself lucky in that either did not occur. You would probably want the first one, since that is about a $75 - $125 (as a guess) job and the other one is a tow and recharge of the hybrid system at the dealer. I cant think that would be cheap.
The car does have a power saver for the lights. It will turn them off after 20 minutes.
I believe the powersaver only works if the lights are in "auto". I once left my parking lights on overnight by mistake, turning the headlight switch to parking lights instead of off. I was quite surprised to see them on when I opened the garage at 5:30am to go to work.
For the 07 TCH, the reading lights in the back are not tied into the 20 minute (+/-) kill timer. Yes, that's right: the two lights within reach of children and constantly left on in the garage don't turn off. For such a smart car, I think that's kinda dumb. So far, I've discovered the car will kill all the other lights (not sure about the trunk) and shut off ACC mode. Meanwhile, over the back seat, two little lights burning bright...
Fortunately, the little 12V battery doesn't have to actually start the engine. It only has to close a pair of relays that allow the car to draw from the big battery. As soon as those relays close, the big battery starts providing recharge to the little battery, which is more than enough keep those relays closed. And the big battery is what starts the gas motor.
The real, serious problem happens when the big battery goes dead. Then it's a flatbed to the dealer, who calls the regional battery guy, who brings the special charger to the dealer. Last I heard, the dealers don't have those battery chargers. There's nothing special about those chargers, except that they are high voltage, and there are several modules that must be hooked up correctly, and if you do it wrong the shock can kill you. So Toyota wants to be sure the tech has good training and all the right safety equipment. They don't want mechanics who are not trained as electricians, and who wouldn't do it very often, to do that procedure. The tech uses "1000-volt" gloves, rubber blankets, and other protective gear to prevent deadly shocks. The safety equipment is the same stuff that electric utility linemen use to work on power lines.
That's interesting, I was wondering what that small battery did in the car. I knew it did not start the motor since there is a bigger battery that did that, so that is good to know. Considering that, it makes sense that the smaller battery is smaller than one would normally find in a car of that size.
Thanks for the info.
So with that information, it would stand to reason that the smaller battery would not need to be replaced as often since there are no serious charge discharge cycles. So has anyone had to replace that smaller battery yet?