Wiring battery fairy lights to usb power

[taa800]

I have a set of fairy lights that use 2 2032 batteries to power them. That's a total of 6 volts. I'm trying to wire them so I can plug them into the wall and since usb puts out 5v, I thought that would work. When I wire it up and plug it in, the lights are much brighter than they are with new batteries, and they are slightly warm to the touch. I would have thought with having 1 volt less going through them, they'd be dimmer, not brighter. What am I missing here? Everything I read online talks about voltage and never mentions amperage. Is that something I need to be considering?
Thanks

 

[Pommie]

It could be that the batteries are in parallel or the load causes a voltage drop. Try adding a 1n4001 (diode) in series with the LEDs. If it doesn't work, turn the diode around as they only conduct one way.

Mike.

 

[Visitor]

The current from 2032 batteries is limited, so a USB power supply will supply much more current. You'll need a series resistor to use a USB supply.

Big Clive on YouTube has modified a number of LED strings and fairy light strings to run from USB battery packs. He explains the brightness/battery life tradeoff well and goes over what value of resistors to use. Highly recommended watching.

 

[audioguru]

Measure the "6V" from the two weak little 2032 batteries when the LEDs are lighted. It might be 3V to 4V, not 6V.
Look at an Energizer datasheet for a CR2032 weak little battery cell. It is designed for a load of only 0.19mA which is close to nothing. Fairy lights overload it.