Bought it used off eBay so not sure if I have OEM parts, but I went from 37% battery to 70% in 4 hours. Slowest charging phone I've ever used.
I did a Google search and found this is a common problem and you need the correct charger and cable. My problem is I can't find any recent information on this and with the stuff I read, there was never a clear answer given.
Has this issue ever been figured out and if so, what charger and cable do I need to get?
It's just the way the pinout is on the cable I believe, if the phone sees it as a standard USB cable such as those used to connect it to a PC, it will go into slow charging mode as to not overdraw the USB port on the computer. The stock charger, and from some other phones, allow the charging at the full ~2A rate.
It isn't a 'problem' at all with the phone. As with any device, technically you should always use the accessories made specifically for it to get the best functionality. Or, at least buy a 3rd party item that is made to the same spec.
Ok so I used my moto x USB cable and the g2 turned into the fastest charging phone I've ever had. I didn't know a cable could make a difference. Same wall charger.
So is there a certain type of cable that I need?
As you've discovered, the G2 (and many other USB devices) can request far more than the 500ma provided by traditional computer USB ports. For non-Apple devices (they broke the spec -- thanks Steve!), shorting the D+/D- pins will indicate to the device that it's plugged into a high power port, allowing it to request far more amperage.
There are specific "USB charging cables" that short these pins for you, if you don't feel like rolling your own. I bought this one:
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