[One (M7) Android Development] trjlive:
Not sure if any of this applies to you guys with charging issues, but I've been seeing some similar posts recently, and wanted to share some info that might be relevant, or at least informational to others who haven't posted about their charger questions.

You need to be really careful with aftermarket and cheap chargers bought online. Often, these chargers are made with inferior parts, and don't supply constant current that is what the device requires. And even using old chargers from past phones that required less power can be a bad idea. Most smart phones on the market these days use a 5V out USB-style adapter. You'd be hard-pressed to find a USB charger that fits your phone's micro-USB port that doesn't supply 5V out.

But the amperage is where it's important to check. Chargers for older, non-smartphones are often only supplying 200-500mA. The HTC One, and most other mainstream smartphones use 1A (1000mA) to 1.5A chargers. Tablets often use 1.5A to 3A depending on the size of the tablet. Using tablet chargers for a cell phone is just fine. The amperage number is the max the charger can supply, so if the phone is only pulling in 1A using a 2A tablet charger, that's just fine.

Where you can have problems, is if the charger is only 200mA, and the phone is trying to pull 1.5A. It doesn't just cause the phone to charger slower, as many people think. Ask an electrician about how capacitors, amperages, current, etc. work and they'll tell you this same thing. Using a charger with a higher amperage rating is fine, but using one that is significantly lower is a big no-no!

It can cause problems with the digitizer which uses electrical resistance to measure your touch, as well as putting increased strain on the electronic components in the device. While it might seem like that old 200mA charger from a 10-year-old Moto flip phone is working fine, albeit slowly, it's actually causing the electronic charging components to operate outside of their designed range, resulting in reduced lifespan for the charger, increased heat and possibly melting the charger, possibly damaging the device, and most definitely causing increased wear and tear on the battery.

A little OT...

Last year, my girlfriend and I were vacationing in Las Vegas, and we left the charger for our Galaxy Tab 2 tablet in the hotel room, and didn't realize until we got home. I had another USB cord for it, but not the AC adapter. So I just plugged it into the same adapter as my phone. It seemed like it was slowly starting to charge. Later that evening, I actually smelled hot plastic, and went to see where the smell was coming from. The tablet wasn't charging anymore, and both the tablet and the charger were extremely hot, and I could smell the plastic burning. I disconnected them, and after the charger had cooled down, it never worked again. Ended up ordering a new Samsung charger from Amazon, and now I always use the official chargers.

I pried open the dead charger, and there was quite a bit of blackened parts inside, along with significant plastic discoloration. The tablet had tried to pull way too much current through the small cell phone charger. Ever since then, I've always looked at the back of the device, usually near where the charger would connect, it will detail exactly what the current requirements are. As long as the charger meets or exceeds what the device needs, it'll be fine. But don't use an underpowered charger with one of your new, higher-power-requiring devices. Chargers are so cheap, even the official ones, compared to a damaged device. ;)

/OT