Originally Posted by VStromNC
I almost gave up using my new Galaxy S4 as a Car GPS due to charging issue. My setup was one of those bullet shaped 12v to USB adapters that you find everywhere. Mine had a dual output- First is 1 amp and the second output is labelled as a 2 amp. I was also using one of those retractable USB to microbus cable.
While trying to Google maximum power (current) draw of my S4, I came across this article and basically, it talked about how the smartphones are now able to sense your voltage and current output including your cable capacity to determine the charge rate. Lot more to it but good stuff.
I changed my retractable USB cable to a high quality shielded type and took it out yesterday. With display on the highest setting and with GPS running, the battery actually started charging using the 2 amp output.
Previously, the battery was discharging with the only difference being the USB cable. I tried the 1 amp output and it started to slowly discharge. My Galaxy S4 AC power supply that came with the phone output is rated at 2 amp and so using 1 amp is simply not sufficient.
I had it our about an hour and worked great and the battery was fully charged.
The article below is really for geeks but interesting reading nevertheless.
Thanks, good information. I may have to revaluate as it seems that simply shorting our the data cables doesn't cut it anymore.