i've been using my 15" lenovo g710.. and its a pain.. to big etc..
i purchased a refurbished ebay off lease lenovo t450s (any "s" is fine because it has MUCH better resolution) and much to my surprise it has 2 batteries (internal and external )--- i've run 6hrs at full brightness .. reviews claim 10-12... maybe when new
i wanted i5 (good power management) has i7, FAST clock (has 2.6ghz boost), 8gb of ram (has 12) and MUST have SSD (has just 128)
mine didn't come with windows, so i reinstalled via the microsoft usb boot utility .. and used my OLD laptop windows key (win 8) hollagram sticker on the bottom and it worked
all for $229, its much brighter and clearer.. plus its small rugged and a pleasure..