Originally Posted by Mrs_Often
Yay at getting a new one! But...
Oh my, 4 days!! That is horrible! You won't know until you've had a couple of full battery cycles though but still, doesn't look good
As for sideloaded epubs, see below.
I'm absolutely positive that battery drain can
be caused by a data file. I tested myself, and I know that kepubs are read by loading a full chapter into cache to accommodate fast page turning. So the longer the chapter, the more has to be stored in cache and the more battery charge is used. I have found two badly formatted kepubs so far that had multiple chapters per chapter (so lots of missing chapter marks), causing a lot faster battery drain than expected, and Kobo acknowledged this and also gave me a refund for both books.
The epub version of the kepub drained the battery a lot less fast, so apparently either the epub reader is more efficient or an entire chapter isn't loaded to cache for epubs; I don't know how it works. So VelvetElvis, no, I don't think it's "just" sideloaded epubs that have these battery issues.
(If you'd like to try it out with kepubs: "Absolute Power" by David Baldacci and "Raven Black" by Ann Cleeves both lack a lot of chapter marks in the kobo store.)
And the sleep/off difference: yes, of course you'll get longer battery life if you power off instead of sleeping. But 4 days of battery life in sleep mode is ridiculous. And, comparing with my Touch: it's been on constant sleep mode now for 9.5 days, with a book loaded, and its battery is at 74%. That gives an estimate of 30 days of life in sleep mode.
Before firing off another email to Kobo, I did a factory reset, updated the firmware, again, and installed a book from the Kobo store. Then I let it sit. After a couple of promising days, I installed a single book (the same one I had on prior to the reset.) Still no problems.
Last night I installed 3 more. But when I disconnected/reconnected, then started Calibre, no books were to be found. Evidently it's a Calibre issue, so I'm hoping today's weekly update will fix that.
So it appears, for the time being, the rapid discharge issue is fixed. If We can get Calibre to find the books I loaded, and battery life begins to approach that of my Sony PRS-T1, We'll be happy campers. Based on my GF's Touch, and now Glo, I don't think it will quite achieve that.
Keep us posted on your Kobo replacement quest.