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Safety

Will the battery or charger be damaged if I use a 1A charger to charge a 2.1A appliance?

Will the battery or charger be damaged if I use a 2.1A charger to charge a 1A appliance?

Duration

I have tried both of the above. What I notice is that when I use the 1A charger to charge the 2.1A appliance, the charging time is extremely long. I understand that because Q = It, a smaller current would take longer to deliver the same amount of charges.

Conversely, when I use the 2.1A charger to charge the 1A appliance, should I expect the charging time to be shorter, or the same as if I used a 1A charger?

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  • \$\begingroup\$ (1) The topic has been thoroughly addresses in this thread. (2) off-topic → use \$\endgroup\$ Oct 27, 2014 at 3:30

1 Answer 1

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A properly designed charger will not take any damage (apart from maybe a blown fuse) if the load is too high. That of course does not apply to 2$ charges from China..

The current rating of a device usually is the maximum current it consumes, given the specified input voltage (range). So no, using a 2.1A charger on 1A device shouldn't change the charging speed.

This applies in the general case, where a "charger" simply is a constant voltage source. There are some exceptions to this though, so be careful, unless you know what you're doing.

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  • \$\begingroup\$ Using a charger capable of outputting 1A max to charge a device which draws 2A may result in the charger overheating. Please use caution in this configuration. You could also place an ammeter inline to determine exactly how much current the device draws when charging. Then you will know what the charger's max current rating should be. \$\endgroup\$ Oct 27, 2014 at 2:01
  • \$\begingroup\$ A charger that overheats is not properly designed. Decent chargers have over current protection, which kicks in if the output current reaches dangerous levels. \$\endgroup\$
    – svens
    Oct 27, 2014 at 2:08
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    \$\begingroup\$ My point exactly: as you mention the $2 chargers are probably NOT properly designed :-) \$\endgroup\$ Oct 27, 2014 at 2:09
  • \$\begingroup\$ Is that because the device "pulls" current from the charger rather than the charger "pushing" the current to the device, which will lead to overheating if the load is too high? (And vice versa, a small load will "pull" a small current from the charger so there are no positive or negative effects from using a 2A charger on a 1A load) \$\endgroup\$
    – t.c
    Oct 27, 2014 at 2:17
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    \$\begingroup\$ You can think about it like that. More formally, the charger just provides a fixed voltage. The more current the device uses, the harder the charger has to work, in order to maintain that voltage. An overloaded charger will either shut off, provide a lower voltage (most devices use less current with less voltage and the system stabilizes at a lower voltage) or stop working/burst into flames (the 2$ version). \$\endgroup\$
    – svens
    Oct 27, 2014 at 2:25

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