Big difference in charge speed between usb car chargers
I've tested two different car chargers, charging the Galaxy S4 at low battery in the car:
- Energizer CC15141: 460 mA
- Cheap dual usb ipad charger: 1200 mA
The dual usb for ipad allows up to 3.1 A top one or two at the same time.
The Energizer is up to 1 A
I guess the dual usb for ipad emulates wall charger, while the energizer does not, so the difference in charge speed.