The advantages of AA batteries are quite obvious. They have a large power capacity (compared to coin cell), they are cheap, and very easy to find should you need a replacement in a hurry. This is precisely why some Beacon / iBeacon vendors decided to opt for AA batteries to power their Beacons.
So why didn’t we? The reasons are also quite obvious.
This inevitably makes your Beacons much bulkier than they need to be. Instead of a small sexy Beacon design that can blend into your venue –you’ll end up with an ungainly eye-sore that everyone one will notice the second they enter.
How much more reliable are coin cells compared to AA’s? Just ask a heart surgeon –there’s a reason they use coin cells to power pacemakers! They simply don’t fail on you (unless you mess with them of course). This reliability factor also segues into our third reason for choosing coin cells.
The reason for this improved performance is simple. Coin cells (because they are so reliable) will discharge it’s power at a consistent rate, all the way until it is (almost) completely discharged. If you take a look at this power discharge graph from a coin cell battery (thanks Nate from sparkfun.com for your Battery Technologies article) you will see that the power discharge level remains almost the same all the way up until the battery is completely drained.
Take a look at this same power discharge graph (thanks houseofbatteries.com for the AA-specs) for an AA battery. See the difference? The power discharge level starts to go down significantly before the battery is even half drained. Why is this important to understand?
When the iBeacon is unable to draw consistent power from the battery –it creates performance issues. This means less signal range, and much less signal stability. Unless of course you plan to change your battery half-way through their lifespan. Then what was the point of getting the higher capacity battery in the first place?
For all the reasons stated above, this is why we stick with the coin cell batteries –and so should you.