one of the big things with liFePo4 is the fact they have less votls.. decent power loss over lipo of about 10-12%
and with the charging time with LiFepo4 say like this pack http://www.hobbycity.com/hobbycity/s...C_LiFePo4_Pack with a 5A charger your battery will still take 54min to put back 4500mah
you will only have the 15min fast charges if you have the charger to support that
and most chargers have a 5A max setting