I have seen a lot of information on building over charge and over discharge protection circuits, and I want to power my Arduino board just like any other device. I want enough battery power for a decent amount of data collection time, and of course the ability to plug in and charge without interrupting collection. For the battery, I was hoping I could take several old smart phone batteries and connect them (IE: 2Series 2Parallel). Most batteries I have found are simple enough, but the iPhone battery has some built in circuitry. I have put a pretty decent effort into Google-lurking in regards to this, but haven't even seen anyone else asking this question. Is it possible to repurpose the iPhone battery, or should I save myself some pain and take it to the recycling center? Thanks!
Connecting LiPo cells in series and parallel has to be done carefully and requires you to monitor each cell's voltage separately and prevent them getting out of balance or any individual cell being over charged or over discharged. It's not at all like NiMh etc where the batteries will more or less look after themselves as long as you don't abuse them too much. Unless you're really confident about your understanding of how to manage LiPo batteries, I suggest you stick to LiPo batteries and charger combinations that are designed to work together. Even if you do that, unless you have a really smart charger and are charging it slowly it's best to have somebody keep an eye on them while they're charging. These batteries are thermally unstable, and volatile, and flammable, and under pressure. When things go wrong, they can get quite nasty.
Thank you for the sound advice, I will move in that direction!