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# What is the best way to power a usb device with 2 batteries? Answered

My project is to make a walking stick with a tesla ball at the top.

I wish to power a plasma ball ( like this one http://www.amazon.com/USB-Plasma-Ball/dp/B0052GSQ8A ) with just two batteries. The whole minty usb charger seems like overkill and meant for smartphones. This is a simple device that runs on 5v and 350ma. But I could not find any instructables anywhere for this.

I do not mind using 3 or 4 batteries if need be. Any link or suggestion would be greatly appreciated.

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## Discussions

For something like that, you could probably just run it on a stack of 4 AA batteries. The nominal voltage for 4 AA batteries in a series is 4*1.5 V = 6.0 V, but I don't think the plasma globe circuit will mind whether it is getting 5V or 6V, or any voltage in that range.

By the way, I think I have the parts for this.  If you are not convinced what I have described will work, I'll slap one together, and take a picture of it for you.

https://www.instructables.com/file/FCE4OB5H0OJ0NLV/
https://www.instructables.com/file/FUZFD2YH0OIYYV5/

I put an ammeter in series with the battery so that I could see how much current was being drawn.  The numbers were bouncing around quite a bit, so I am going to guess the actual current was in the range from 250 to 350 mA.

I did not bother to measure the voltage.

Guessing that this setup could power the plasma globe for maybe 2 or 3 hours, but that's just a guess.  You could of course get more run time by using larger batteries; i.e size C, or D, instead of AA.

More voltage isn't a bad thing. I've ran my USB plasma ball off a 9V wall wart that actually puts out close to 15V. Now at that voltage the whole globe is just pink from the plasma. Gets interesting when you cover it in foil or try to place a coin on top. If you have good ruff hand you may not feel the arch's of electricity but you will smell your burning flesh and see nice black pin sized burns on your skin.

Mintyboost is pretty much a really easy and nice solution for USB powered things, where you NEED to use 2 batteries. If you can use 3 or 4 batteries, just hook up 3 AA batteries in series and hook it up (it should power on). If it doesnt turn on, go up to 4 batteries and a LM7805 regulator.

When in doubt, look to the right. Meaning the related bar. Or more specifically the last item in the related bar.