Hi, I think ... My new electric car will have two batteries A big one for 400 Km - 250 miles a little second battery for 50 km - 30 miles Why second one ?? ... Easy to change battery (at home?, at technical service?) Used for charging my car with low power plug or low time ... Solar pannel or Wind power (Low Amp) Or charge only a few minutes (Big Amp but low time) I think it prevents stress the main battery... See you Jorge Post Data: Perhaps in 5 or 10 years I'll have one.