DIY: Disconnecting You Car Battery
Disclaimer:
These are some tips that have worked for me. If you follow these tips, you do so at your own risk. Please be careful and take all appropriate safety measures.
I do a lot of work on my own cars. As such, when dealing with electronic items, the rule of thumb is to disconncect the battery. I suppose this is to prevent an accidental short, or shock. Anyway, the battery cables in my Mustang are kind of stiff and have a tendancy to flop back onto the battery when disconnected. I found that a spent toilet paper tube (or paper towel roll) fits nicely over the end of the loose battery cable. This insulates the battery from an accidental touch in case the cable flops over and hits the terminal(s).

