Your iPhone only requires a 1.1 Amp charger. Your iPad Mini 4 requires a 2.1 Amp charger. The large iPad requires a 2.4 Amp charger. My guess is that you have a 1.1 Amp charger.
Note that it does not hurt any of the devices to use a higher Amp charger than they came with (i.e., you can use a 2.4 Amp charger on any of the "i" devices).
See this link:
http://ipadpilotnews.com/2014/01/cha...tips-air-mini/
Check out this one: https://www.pilotlights.net/dual-usb...st-charger-48a
"Built for rugged use in any 12 or 24 Volt vehicle, it provides 2.4 Amps of charging power to both USB ports (4.8A Max, 60W). A combination of internal over-voltage, over-current and internal UL-approved fuse provide superior protection of your devices while charging. FCC approval ensures the device won't create RF interference with nearby electronics and radios. Designed for use in Aviation, Commercial Vehicles, Marine, Utility applications and Automotive use."