It's time for me to replace the battery on my Aura. After doing a lot of searching coming with almost nothing on how to remove the backing of the Aura or what type of battery is in the Aura, I ran across this Youtube video on a N514 teardown -
I went about it the same way and got access to the battery which is glued down.
Next I noted the model number of the battery (pr-285083) which I found out that it was the same battery that was in the Kobo GLO HD as well as the NOOK GlowLight Plus BNRV510. A few eBay sellers are selling the battery for less than $15 US Shipped. From the looks of the images included in the auctions, even the battery connector is the same so there shouldn't be any need for soldering.
