Car mods come in many forms -- including, even, a piece of cardboard with some switches and an LED display. The car being modded in this case is the Nissan Leaf, and the mod in question (still in its temporary form here, thankfully) is a simple but important one. It's a homebrew device that plugs into the Leaf's OBD-II diagnostics port and displays the battery's exact state of charge, as opposed to the somewhat less specific bars that are displayed on the main dashboard display. Absolutely necessary? Not exactly, but the mod seems to be catching on with a growing contingent of DIY-minded Leaf forum members. Hit the source link below for a few more examples and some additional details for building your own.

[Image credit: mwalsh / My Nissan Leaf Forum]