Allow me to restate. I believe that the purpose of the evextend is to use the 12V Battery as an emergency battery to get you extra miles too get you to a charging location. Assuming the 12V is fully charged, what is the extended range? What is the calculation?
So, using the EVExtend, or one of the alternatives to hook up the 12V battery to the engine system battery, how many miles should I expect to get, assuming I have already totally exhausted the engine battery. BTW, how big is the system battery?