Is there a way to use a car charger to charge the phone at a good rate while still allowing data to, say, a car's usb port? This would be very cool if it is possible.
Using the vehicle's USB port will charge, but it all depends on the AMP output of that USB port. It's not going to be faster than or even close to a real car charger.
Right, that's why I ask... The output from a standard USB port is only enough to charge a 6P very very slowly, I was wondering if there's a way to charge faster while still being able to use usb data. I bet its technologically feasible, but I doubt any such devices exist.
Sure, get you a GOOD car charger, then stream your music via bluetooth... I'm not sure why you'd think a USB type-A port to output more amps than it should... the USB is not going to output at that high of output.
Looking at a discussion about the output of the USB port in a Mazda3 (though it's possible that different years would have different output, especially with the recent redesign), it sounds like your phone may be able to draw enough charge to maintain its battery level, but not really increase it.
https://www.reddit.com/r/mazda3/comments/3bisc4/anyone_know_what_the_output_amps_are_on_the_usb/
Mine's a 2014. I haven't measured it, but yeah I imagine its only enough to charge very slowly. For comparison its enough to charge the Nexus 5 at around 1% every few minutes... Quite slowly. Hence the desire to somehow source more current (as with a car charger) while maintaining the data link.
Only thought I've had is if you have a power inverter, and a powered USB hub with a port made for charging a phone/tablet, you could set things up to see if the USB port will even support a hub. That's the only even remotely possible option I've come up with - an in-line device that adds current, the only example I can come up with is a hub. I have one of these hubs ( Amazon.com: Anker® USB 3.0 7-Port Hub with 1 BC 1.2 Charging Port up to 5V 1.5A, 12V 3A Power Adapter Included [VIA VL812-B2 Chipset]: Computers & Accessories ) in my office, and port #7 is 2a, much better than the likely 500ma of the built in port.
Side note, I'm a big fan of the 2014+ Mazda3. Had to buy a newer car for my wife recently, and I'd hoped to get her one. Unfortunately, cost (due to them being newer) and location (closest Mazda dealer is ~2hr away) dictated otherwise and she got a Chevy Sonic hatch.