John, this stuff shouldn’t matter.  The batter is going to provide only what 
the drain is, not more.  You’re playing with I on the E = I * R equation 
remember.  Good ol ohms law.

> On Sep 6, 2015, at 3:03 PM, John Weir <[email protected]> wrote:
> 
> Aman: in the 500ma case below, on the USB there is no handshake on the data 
> lines, the device has only 5 and ground, does that matter? it was designed to 
> use a 120v ac charger with 5 volts 500ma DC output. I am wanting to extend 
> life from 5 hours to about 15 with out recharge so connecting to external 
> battery. Will the Anker  or any other such battery need some sort of feed 
> back?  John
> 
> On 9/6/15 8:19 AM, Aman Singer wrote:
>> Hi,
>> The amperage of output noted on a USB five volt battery indicates the peak 
>> output if the device requests it. These batteries can charge any usb powered 
>> device using standard protocols, keep in mind that some devices use only a 
>> hundred miliamps  and others use three amps. The usb specification, even on 
>> computers and wall chargers, needs to handle such differences between 
>> devices gracefully.
>> Hth,
>> Aman
>> 
>> 
>>> On Sep 5, 2015, at 11:11 PM, John Weir <[email protected]> wrote:
>>> 
>>> Need to understand them. Been looking at Anker batteries.  Do they self 
>>> regulate their output? ie  I have a device that charges off the plug in 
>>> power supply at 550ma.  IF I use an external battery charger that can 
>>> supply 1 or 2 amps , is this spec the possbile peak rate while the battery 
>>> charger only provides 555ma to my device then if I have an iphone needing 1 
>>> amp it provides one amp?  Ie I dont want to over heat and to blow up a 
>>> iphone or other device small battery that usually charges at 550ma by 
>>> hitting it with 1 or 2 amps..    How do they work?  John Weir
>>> 
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