Oh, here's the battery disconnect I have been using on my cars for years. It also works as an effective anti-theft device as you can take the screw knob with you, leaving the power cut off.

Here's the one I use for about $5 on Ebay:

Item number: 120166177834

http://cgi.ebay.com/ebaymotors/BATTERY-MASTER-DISCONNECT-CUT-OFF-IMMOBOLIZER-SWITCH_W0QQcmdZViewItemQQcategoryZ33574QQihZ002QQitemZ120166177834QQrdZ1QQsspagenameZWDVW#ebayphotoh osting

__________________
Rick

'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac