Objective comparison between emergency usb chargers

[Laszlo KREKACS]

On Fri, Aug 14, 2009 at 12:11 AM, Ed Kapitein<ed at kapitein.org> wrote:
>> I hope we can collaborate, collect useful data and publicate
>> them. Im very tired all these cheap half-finished electrical
>> devices (I can only charge 27% from a 3500mAh 3.7V
>> accumulator! It is insane!)
>>
> i think 3.7 V is just not enough to charge the freerunner, in need to be
> 5.5V  if i am not mistaken.
>> I also want to collect the *efficiency* of the charger backed up
>> with some measured data.

The charger itself internally has two 3.7V Li-Ion battery parallel connected.
There is an internal circuit with some DC-DC converter to deliver the
correct 5V output.

The problem is, that FreeRunner's battery is 3.7V 1200mAh(4.44Wh),
that charger's battery is 3.7V 3500mAh(12.95Wh), so no matter
how efficient the internal DC-DC converter it should charge at
least once the freerunner. (with 50% efficiency we still
have 3.7*3.5*0.5 = 6.48Wh power what the Freerunner get at the end).

So if it cant charge the Freerunner at least once, something is
seriously fucked up design-wise.

Best regards,
 Laszlo