I have seen chargers rated at up to 2400mA, so I wonder, whats the max that Smartphones will accept while charging? I ask because I want to buy a charger that is able to supply the absolute max my phone requires. My phone for example is Samsung S4 mini. I assume its not much above 2400mA and constantly decreases while charging? or for example does anyone know how much the Powerbanks by Anker pull maximally? Also I just bought a charger with 3 USB plugs and it says: maximum current per Slot: 2.400mA, but 3.400 Ah batteries are common. So I wonder, why did they limit one port to 2400 mA - is that a common limit of li-ion and li-po batteries?


closed as off-topic by Leon Heller, PeterJ, Adam Haun, Nick Alexeev Jun 24 '15 at 4:20

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    \$\begingroup\$ mAh is not power, it's energy. Are you asking how much energy you need for a full charge , or how much power the phone draws during charging (which varies with charge time)? \$\endgroup\$ – Mister Mystère Jun 20 '15 at 13:36

The upper limit on what current a phone MIGHT accept is the limits set on battery charge rate by the battery manufacturer. The upper limit for LiPo or LiIon batteries is usually C/1 = 1 mA of charge current per mAh of battery capacity. A very few battery manufacturers allow higher charging rates but this is rare enough that it can be ignored.

So - a phone charger will usually limit charge rate to either C/1 (eg 2400 mA for a 2400 mAh battery) OR whatever lower limit a charger may set.

Your S4 Mini may have a battery of about 1300 mA capacity. If so, the maximum rate will probably be 1300 mA. When charging from 'flat' a charger usually charges at C/1 until the battery voltage reaches 4.2V, then charges at a fixed 4.2V until the current falls (under battery chemistry control) to typically C/4. The actual "terminating rate" varies with design. C/2 cutoff gets slightly less capacity but much longer cycle life. C/10 cutoff get about 100% capacity at the expense of reduced cycle life.

Most smartphones have under 2000 mAh battery capacity so a 2400 mA max charging port is fine. Tablets may have much larger batteries. An iPad typically has 10,000 mAh or more of battery capacity. To charge a 10,000 mAh battery at the 10,000 mA the battery would accept takes special care and design and most chargers will not provide this level of charge.

  • \$\begingroup\$ Thx, very helpful answer. \$\endgroup\$ – Peter Fleix Jun 20 '15 at 18:14

First, mAh is not power, it's more like battery capacity. Charging current may vary and it depends on many factors. But, it always is measured in mA. About your charger. Probably they have a DC/DC component, rated for 3.4A, but connectors or whatever components that are i series to the connectors, are rated only 2.4A. So it's not much information, as you don't know, how much current your phone takes. In my experience it's ok to assume 1.5A for charging not from a PC USB. So two phones at a time is fine, the third port is safe for very low power device, maybe a handsfree or headphones.


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