Dom,

I've been using dual PC680's for 4 years now (2 years building, 2 years flying).  I replace the main battery with a new PC680 every annual and move the 1 year old Main battery to the Aux battery position.  (I have a fully electronic ignition and EFI, AKA Aero-Electric Z-14.)  Then I take the 2 year old Aux battery and put it in my Goldwing motorcycle, and take the 3 year old Goldwing battery and put it in the lawnmower.  I take the 4 year old lawnmower battery to the recycler. So far, the lawnmower has not failed to start. 

 

Mark S.