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Usb battery bank help and questions ? Answered

well i want to add like a battery pack instead of the 9 volt batteries i have now and this a ruff model i made today, but i will make a better case but back to my question is would this work? http://www.amazon.com/Tenergy-2000mAh-Capacity-Battery-Security/dp/B001BA292A/ref=sr_1_11?ie=UTF8&qid=1347244925&sr=8-11&keywords=9-Volt+Rechargeable  or do you recommend something else it has to be rechargeable,  



5 years ago

To do what ?
Run an RC car or a copter or a keyboard ?

How much current then ?


a cell phone charger, just a back up usb battery bank

USB is 5vdc capable of  up to 1 amp.

Cell Phone batteries are 3.3v to 7v what is yours ?

Now what ?

See the circuit uses two 1N5819 Schottky diodes ( 14¢ ) in series to
drop the 5V USB supply on the left side by 1.2 volts resulting
in 3.8 volts on the right for your battery.

The 47 ohm resistor limits the charging current to 80 ma.

If you need more current use a lower resistance.

I didn't use a 317 regulator because it needs a 2 volt difference to
regulate and that would make it impossible to output 3.8 volts..

Don't use another diode because these were selected to provide
the necessary voltage drop...


USB DiodeReg.jpg