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According to two employees at the Sprint store, using an unofficial charger for the Galaxy S4 will negatively impact the overall life of the phone's battery (edit: in other words, the battery will need to be replaced much sooner than if one always uses the official charger).

I've never heard this before. Does anyone else know what they are talking about? What is special about the S4 charger? I saw someone online mention that a "special code" is transmitted over the USB connector, which the phone will use to judge if it is an official charger; again, new to me, but I'm not a hardware expert.

Update: I still haven't figured out an answer to this. Regarding the "special code", the post I saw may have been referring to the IC chip, but I don't know. So if we look at the distinguishing characteristics of a Micro USB Charger, there's 1) whether it has the IC Chip; 2) whether it is 2 amp vs. 1 amp; anything else?

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A li-ion battery is charged in stages. C refers to a measure of Charge which to my understanding is not a scientific calibrated measurement, but moreso a general approximation of how much energy the battery can provided in an hour.

  • If the battery is deeply depleted, we must slowly trickle charge the depleted cells at a rate of < 0.2C to avoid overheating issues. Once the battery cells are at 2.8-3.3V, we can charge rapidly.
  • The rapid charge stage is referred to as the Constant Current stage. The battery can be charged at a maximum rate of 0.5-0.8C. Going above 1.0C does not make the battery charge faster, it just generates more heat which is a killer for batteries.
  • Once the cells reach 4.2V, charging transitions to Constant Voltage charging at a rate of 0.1C or less. Essentially, it is not charging at this point. If the battery is depleted a few percentage points because the charger is smart enough to switch itself off, it will begin Constant Voltage charging to restore the small depletion.

Cheap chargers often don't do any of the slower phases by actively monitoring the voltage, they just deliver 1C or more. When your phone is charged up, this generates a lot of heat. An increase in temperature of 8 degrees Celsius can half battery life. Lithium ion batteries are basically hand grenades, which is why they have so many safety systems built in to vent pressure and avoid overcharging. Cheap chargers also are probably not UL certified and have terrible quality control, so they present a fire hazard.

The phone can probably detect if an appropriate current/voltage is being supplied for the battery's current charge level. The other possibility is that the charger has a data wire(chargers have no need to send data to the phone) and upon connection, a magic number is transmitted that identifies the device as a Samsung charger.

Source: Former Electrical Engineer

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I shouldn't think so. Samsung is a signatory to the EU Common External Power Supply standard, which includes specs for a USB charger. As long as the charger you're using supplies something close enough to what the Samsung one supplies, you're good to go. You can even charge it from a Computer USB port, although it will be quite a bit slower (except some PCs which can supply a higher amperage via a micro-usb cable, making it almost as quick as a mains adaptor charger.)

But in any case, you should be fine as long as the charger is of decent quality and isn't going to catch alight or something. I've been mixing and matching HTC, Samsung, and Blackberry chargers for years now.

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  • Same experience here. The GS4 will give you a warning on a low-power charger, just saying that charging could be slow. But I've never experienced any trouble. Side note: Sometimes on low-powered chargers, it's not enough juice to boost the battery if you are using it at the same time! But the 2Amp chargers usually do very well, and charge it quickly. – Andrew Barber Sep 19 '13 at 18:38

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