Convert 5VDC USB to 9VDC

Thread Starter


Joined Feb 2, 2018
I need to convert from 5VDC (either 1A or 2.1A) on a 20,000mAh battery to 9VDC 750mAh hollow post. Will someone help? I've done web searches and found 12VDC to 5VDC, 12VDC to 9VDC, 9VDC to 5VDC, just about anythingVDC to (anythingVDC except 9VDC).

My project is to replace my wall-wart supplied power with a battery for my 9-band equalizer, which will have my Free Lossless Audio Codec (FLAC) player connected to its input and my headphone amplifier connected to it's output. I'm nearly deaf in the 8KHz+ frequency ranges, and this little equalizer works wonders in boosting the upper-mid range and high range tones.

I think this may work:

Whaddya think?

Thanks in advance for you assistance.
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Joined Aug 23, 2012
How to calculate the values which do they enough for your application?
Input voltages : 5V
Input current : 20A
Input Watts = V*I = 5V*20A = 100W

Convert Rate: 80%-90%
Output voltages = 9V
Output Watts = Input Watts*Convert Rate = 100W*(80%-90%) = 80~90W
Output current = Output Watts/Output voltages = (80~90)W/9V = 8.9A~10A

Products Noted : Max output :9V or 12V 600-800Amh(differs form the devices)
So the current of converter could converts over 9V/750 mA then it will be enough to apply for your load needed.


Joined Jan 8, 2017
I think that would do what you want. You will probably find many step up converters such as this one on Ebay which will also do what you want.. Those sold by sellers in China are normally the cheapest.



Joined Dec 23, 2017
hi duncster , i am curious about your 5V/ 20AH battery . what type of cells? , can you put them in series to get 10volts
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