My Voyage does the same, every time I charge. I tried different chargers, I tried running down til i got the message. Still the same. Once or twice I might have gotten what almost looked like full, but as soon as I use it for like 2 minutes, its back to missing a chunk. Been doing this pretty much since I had it, over a year now.
Wow, I had this thing for 13 months. Where the heck did the time go
It bugs me too a bit I have to say. Just cause I want full when its full. Hasn't caused any issues. I have to charge every other day anyway. The new update seems to also cause a bit more battery use. But I also read a lot and always have wifi on.
I actually just unplugged mine from the charger and I think its almost full. Its still a tad more white on the right than the left and in a while it will go to the next chunk fast and then go more normal. Maybe one of these days I'll let it run down again. But I am a bit OCD about not getting to low on it. Can't explain it, I just don't like it. I start obsessively tap the top to see where I am at when I get to low and then I can't concentrate on my book.