All the company vans have had LED installed lights in the cargo bay where you put the storage stuff.  I put a light switch inside the cargo area above the side door in the sleeper bin and also inside the cabin for the driver.  There is a warning green light that lights up in the cabin under the radio when the power is being used for the LED lights.

The LED lights take up lots of battery power.  If not using the LED lights turn off the switch = No Green Light.

I do not recommend to have the cargo LED lights for more than 30 minutes without the engine running.  If you are working on the van and need the LED lights on longer than 30 minutes, wheel chock all wheels, start engine, put gear of van or truck in neutral if manual, put the park brake and emergency break (if available) on and run the engine while working on the van more than 30 minutes.