Hi, all, I am making a battery bank for my gf; she lovers her apple products. The battery will have no ports, only a single short male lightning connector wire protruding that will serve to plug into an iphone or ipad to charge. I already have that working fine. I just use an ultra small high efficiency boost driver and 5V and GND is supplied and it charges great. My idea is to use the same connector to charge the battery with my own external charger. This way the battery is as small and light as possible. (it will be about 294g for 69 Wh or 19,000 mAh and 110x66x20 mm) To do this I need to use one of the pins for ~4 volts out (range 2.6V-4.2V). Is there a pin that I can use that will always have 4 volts and not damage or mess with an iphone or ipad?