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I've recently got a new Samsung Galaxy A5 (2016) running Android 6. It's great, but I'm not sure how to charge it properly.

By using the charger that came with the phone I get a notification saying "Fast Charging" and the phone heats up like crazy so it can shorten the life of the battery (although it does actually charge really quickly).

Alternatively I can use 3rd party chargers (none of which obviously suport fast charging), but many websites say it can harm the battery because they can be of really bad quality, so I don't like that option.

The best option I see is to charge it using my PC, but I can't have my PC everywhere I go and leaving it on overnight seems like an energy waste (no, my PC can't charge when it's off).

Disabling Fast Charging seems like a good idea, but since the Marshmalow update, the option is not in the settings anymore.

The text on the stock charger says:
Input: 100-240V 50-60 Hz 0.50 A
Output: 9V DC 1.67A or 5V DC 2.0A

With all that in mind, what is the best way to charge my phone and do minimal damage to the battery in the long run?

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  • Try keeping your phone in like tables or other hardened places (Not on a blanket,pillow,bed or any soft clothes). This helped me!
    – Pramesh Bajracharya
    Dec 23, 2016 at 18:25
  • Upvoted for caring for your battery !
    – beeshyams
    Dec 24, 2016 at 3:54

2 Answers 2

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You have multiple options :

  • Power bank that doesn't support fast charging

  • Normal 5 V 2.0 A or 5 V 1.0 A charger ( since fast chargers are backwards compatible )

  • Using a USB hub between charging port and device

  • Using a custom kernel that can lower charging current ( if device is rooted)

  • Using a Power only ( no data ) cable

As confirmed by OP, the last option worked and they wanted to know Is it safe?. To answer that, we need to understand how such cables are designed

  • A Power only ( no data ) cable uses Pins 1 and 4 ( refer USB layout )

  • Which means pins D + and D - are NOT used. These pins are responsible for negotiating the power requirements - (see Overview of USB Charging for more details )

  • Li Ion batteries charge in stages ( see Figure 1 ), which means that different voltage and current levels are required at each stage. Stage 1 corresponds to < 20% and Stage 3 > 70-80 ℅ ( roughly - from experience )

Since D+ and D- pins are not used to negotiate the power required for each stage, such a cable will provide a constant Voltage or Current at all stages, which is not desirable

From a theoretical point of view it should be OK, if you are charging from 20 to 70-80% , but this may not be practically feasible. So, it is safe , IF, you ensure this charging limits

From a purist point of view ( as your question indicates), it is safer for battery to use the option of using a normal charger (that negotiates requirements, while charging ) and that is the best way ! You can buy older OEM chargers that charge at 2A

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    Nope, nope, nope. You're assuming the charging electronics are in the charger; they're not. It's just a simple power supply, with selectable output voltages in the case of the fast charger. All the voltage and current regulation going into the actual cell is done in the phone. If not, well, what do you think happens if you hook 5V2A straight onto a Lithium cell?
    – SomeoneSomewhereSupportsMonica
    Dec 24, 2016 at 10:26
  • @SomeoneSomewhere: I know that. How do you read or interpret the answer to imply otherwise? But to make it clear the charger does house the IC that is involved in fast charging mechanism. Else, if it had nothing , how does it charge as a normal charger a device not equipped with fast charging or how is it backward compatible?
    – beeshyams
    Dec 24, 2016 at 11:56
  • Because you talk about the 'stages' of lithium battery charging, which are only seen by the buck regulator built into the phone. It's that regulator that adjusts the current/voltage supplied to the battery. Most chargers do no more negotiation than saying "I'm not a PC, draw as much current as you like until I turn off".
    – SomeoneSomewhereSupportsMonica
    Dec 25, 2016 at 8:04
  • Most chargers do no more negotiation than saying "I'm not a PC, draw as much current as you like until I turn off-- Have a look at Table 4 and Fig 17 here for the negotiation done, which is way beyond Am I a PC or not?. Fact that it is a power bank does not make a material difference- is talking about fast charging and role of D pins // As far as stages of charging are concerned, suggest you read the Overview of USB charging linked in the solution
    – beeshyams
    Dec 25, 2016 at 8:39
  • You may also like to see the various stages and corresponding implementation in battery charger of 2008, when fast charging was not available. You can Google and download "APPLICATION NOTE S3F84K4 LI-ION BATTERY CHARGER" ( caps unintended , copy paste result). Not withstanding this, if you like you may share background for your conclusion. My solution is based on understanding which is supported but there well could be something I am missing. If you like you can point that out in a chat
    – beeshyams
    Dec 25, 2016 at 9:03
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I would recommend getting a Samsung travel adapter which outputs at only 5v.

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