Quote:
Originally Posted by JSWolf
My way of looking at it is that the Voyage and the Oasis use good quality batteries. That being equal, the Oasis battery is 1/6th the size of the Voyage battery. That means the Oasis will need to be charged 6 times more than the Voyage. We know that these batteries can take only so many charges before we notice they don't hold a charge all that well. The Oasis will show this much sooner than the Voyage.
If I am wrong, someone please explain why. I don't think I am, but if I am, I'd like to know why.
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So, there's two things at play here:
1) The definition of a cycle is somewhat important, and it can be used to demonstrate that depending on how much you read, even the tiny battery can be reliable into the future.
2) The cover takes priority over the internal battery. Plug in the cover, and the internal battery stops having power drawn from it.
So let's start with #1. Draining a battery to 50% and recharging it isn't a cycle. Rather it's much closer to half a cycle. Close enough that you can call draining a battery to 50%, and recharging it twice a single cycle. So you aren't wearing it out faster. And because LiIon/LiPoly chemistries don't like deep discharges, you have some control over how many cycles the battery lasts by simply not draining it too much.
Let's assume the internal battery lasts 6 hours of reading, and you read 30 minutes a night. That means you'd cycle the battery once every 12 days. If we also assume 300 cycles (the low end of LiPoly), then we are looking on the order of about 9.8 years. So this is if you
never use the cover. Yes, the Voyage's battery will last longer since you won't be cycling every 12 days in this scenario. But the general thing I'm pointing out is that for someone with a lighter volume of consistent reading will get quite a bit of use out of just the internal battery. Enough that even if you read for 2 hours a day, every day, without fail, you are still looking at 2.5 years before things get wonky. Which isn't great, but isn't terrible for such a small battery.
However, #2 puts a huge wrinkle in that. Since the combined battery has more capacity than the Voyage's internal battery, the more time you read with the cover on, the more it starts to skew more and more in favor of the Oasis. If you spend 50% of your reading time with the cover connected, you are doubling the life-span of the internal battery. 75%, and you quadruple the lifespan. If you leave the cover on all the time, then the internal battery is really only going through the small trickle conditioning that the charging circuits put it though as if it were always plugged in.
So, here's the thing, you are kinda right that the internal will wear down faster, but that's assuming you are in the realm of spending <50% of your reading time with the cover on, and reading at such a clip that you devour books in the way that a particular Sesame Street character devours cookies.
That said, these numbers also assume a fairly low number of charge cycles on LiPoly chemistry. Apple rates their LiPoly batteries closer to 1000 cycles. Without knowing exactly where Amazon's batteries land, I chose the worst case scenario. Even with these worst case scenarios, the battery lifespan isn't really out of line for electronics of this kind. Probably why Amazon was willing to design it this way.
All that said, I probably would have stuck with a Voyage if it wasn't for the ergonomics and asymmetric bezel on the Oasis making for a nicer one handed grip. Sadly, the bezel on the Voyage is about half the width of my thumb, and has always been a bit of a pain since it is flush with the touch screen.