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we have a few LED string lights that use 3 AA batteries and eat through batteries about once a week. I would like to replace the AA batteries with a USB battery pack I have which has about 8,000 MAH. Since AA batteries are 1.5v and standard USB is 5v, is this as simple as cutting an old USB cord and finding the correct positive / negative cables to wire to the empty AA battery enclosure? I am not sure if the +/- .5v would make a difference? Is there an easy way to find out which wire from the old USB cord is + and -? Am I nuts or will this work?

Thank you!

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It will probably be as easy as you are hoping.

Chances are, the red wire is positive and the black wire is negative.

Can't say for certain without knowing more about the LED string, but chances are if it could be powered with 3 AA batteries, a USB will have more than enough capacity. Hopefully there is an inline current limiting resistor to the LED's, and therefore the additional 0.5 V will be dissipated over that. A little more wasted power, but nothing to worry about.

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  • \$\begingroup\$ Thank you Jim! Now just need to find a USB cable to cut :) \$\endgroup\$ – AAA Dec 28 '17 at 0:45

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