There is a Kobo reader forum on MR:
https://www.mobileread.com/forums/forumdisplay.php?f=223 My Kobo keeps a charge for about 10 days of moderate use. Most folks starting with a full charge charge are getting fairly long lasting charges. The 1.0 firmware, not so much--and with an SD card inserted--less. The firmware updates have helped. For lots of help, go to the Kobo forum.