If you use a flashlight like a Surefire, they take the lithium CR123a batteries which can cost up to $5 each. This place
Botach.com sells them for about $1 each if you buy 20. They have lots of other military tactical stuff as well, but the batteries are branded as Sanyo, and seem to last as well as any others. By the way, a 3 cell Surefire flashlight will put out several times more light than a 4D Maglite with or without the halogen bulb. With a 10 year shelf life, I find this to be the perfect flashlight for a car. No affiliation to Surefire or Botach, just wanted to pass on what I consider a good price.
