I would like to add some interior lighting to my '85 Westy. I have found some battery powered LED lights that would work nicely, but they run on AAA batteries at either 4.5 or 6 volts. I don't like the idea of changing batteries and would like to run them off the van's battery. I know that I could hook them up to a selectable voltage dc power supply plugged into the cigarette lighter, but I'd like to find a way to run them off of 12 volts. 

Is there an easy way to run 4.5 or 6 volt LEDs on 12 volts? Some sort of resistor inline? These lights are inexpensive as opposed to ones I've seen online designed for 12 volts which are three to four times the cost. 

What would happen if I ran them on 12 volts instead of 4.5 or 6?

Can anyone point me to a good web site which explains these questions? I've found some LED sites, but none that answer my questions.

Thanks,
Ed in CT