As the iphone drains so fast, I'm wondering why the RC doesn't charge the phone from it's large battery? It's 6000mAh battery would be sufficient to keep the phone charged for a good four hours I suspect.
Would this be a possible upgrade for the controllers?

Possible reason is that additional heat from charging would cause CPU speed throttling to prevent overheating.

The controller does charge my Note.  It is a slow charge but it is definitely enough to keep it from losing charge.

My tablet is charged bij the RC. All be it not fast enough to keep level.