Sonoff electric candle
Simple modification of commercial electric candle and installation of very popular Sonoff Basic relay inside candle to make it "smart". Batteries not needed, entire setup is powered from Sonoff!
First you need donor electric candle. Mine is from european supermarket chain "Lidl" but if Isn't available near you, picture of manufacturer and model is shown below text. Probably any battery powered 4.5V candle you can get is suitable for this project.
Next thing you need is Sonoff Basic wifi wireless smart switch. Remove it from original case and prepare for installation in candle like on picture below. Desolder relay from board because entire candle will be powered from Sonoff. Relay output is 5V but no need for further voltage reducing to 4.5V. Desolder LED from Sonoff board because body of candle is transparent and it will be visible when relay output is active. Sonoff can be used with native firmware but mine is flashed with custom Tasmota firmware for integration to Home assistant via MQTT, procedure to do this is wery vell described by DrZzs.
Open the candle and cut battery compartment for mounting Sonoff board. Also drill a hole for installing power cable and cut out opening on candle body also for power cable.
Fix board and power cord to case, i've used hot glue gun, but any method that will hold parts together is suitable.
Desolder wires from battery compartment terminals and solder them to contacts where relay was placed before. Exact position of terminals shown on picture on beginning of the text. Be careful with polarity.
Put everything back together and you are finished. Enjoy using your new smart candle.