I had a bunch of fake candles that I needed for my new room, The Bayou: Legend of the Midnight Raven, but they all use batteries. In addition, I wanted to be able to control the candles turning on and off. This turned out to be really easy.
Step 1: Replace the batteries
First I measured the height of two AAA batteries, which is what this particular candle used. I then cut a wooden dowel to that same length. I screwed in a metal screw at each end and attached a small wire to each screw.
Step 2: Reassemble the candle
Once that was done I just fed the wires out the base of the candle.
Now it was easy to take the 2 wires and attach them to an Arduino which can produce up to 5V of current. I can then program it to supply voltage whenever I want.
I had to use some resistors to actually get the voltage and amps to the right level, but having them a bit high really just means the LED will burn out faster. You’ll have to figure out the electronics part on your own.