The battery in the iPhone is a lithium battery, right? I've heard it batted around for years that you cannot "condition" a lithium ion battery so that battery life will be improved. Then again I've heard folks who swear after draining their batteries down to where the phone shuts down completely and doing a charge back to 100%...and doing that routine several times in a row has mproved their battery life significantly. Which is correct? My iPhone 6 is getting mediocre battery life, and I would love to get more if I could.