2010 Silverado 1500
I have two LED work lights that I plug into the cigarette lighter outlets of the truck. I use the lights for multiple hours when working under the vehicle.
To my surprise, I've not yet drained the battery to the point where the truck won't start. But I'm wondering if there's a limit.
Will the truck eventually automatically turn off the lights/cigarette lighter to prevent the battery from being excessively drained?
According to the specs linked in your question, the lights will operate to as low as 10v. It's unlikely that your convenience outlet has low-voltage protection. This means that the lights will be able to drain your primary battery to as low as 10v before they cease to provide illumination.
Ten volts is far lower than considered safe for conventional starter batteries. With a rating of 42W, the lights may draw as much as 4A while being used, allowing for inefficiencies and wiring losses. It's safer to err on the pessimistic side for calculations of this nature.
You could perform a real-world test by using a clamp-on DC ammeter and observe the current draw with the lights on and off. That would give you a more certain basis for the math.
Examine your battery to determine the amp-hour capacity. For an example, I'll use the easy math of a 100 Ah battery. You don't want to drop below fifty percent discharge for a lead-acid battery, giving you fifty amp-hours with which to work.
The four amp draw in a fifty amp "fuel tank" means better than twelve hours use before you should be concerned.
The answer to your question is No, the truck won't turn off the lights. The real answer is Yes, you can excessively drain your battery.
@Fred answer contains the basic math.
On the other hand, be aware that a starter battery as dead as having only 5% of its nominal capacity is capable of flawlessly starting most vehicles when charged to the top of its still alive 5%.
If your battery is new and healthy and has no other reasons to be undercharged when you start draining it, you can rely on it having at least 50% of its nameplate capacity.
On the other hand, an old, but still perfectly working battery could in fact hold very little charge and serve you a surprise after a very little draining.
Be also aware that a general starter battery has a limited cycle life, as low as 20 or 50 cycles when discharged down to 50% (discharging it deeper makes the things much worse).
If you like to systematically use electricity out of your vehicle battery with the engine off, consider getting a deep cycle battery instead of a pure starter one.
