This X-Mas in Ukraine was ... not perfect. But we still wanted to have holiday so we had IKEA battery powered fairy lights. Those were both festive decoration and backup light for hours when there were power cuts.

But amount of AA batteries those lights were chewing through was annnoying me. And I hate using recharagble AA cells since those are taking ages to charge and you manually need to pull them out of the device, charge, put back.

So I decided to make a device that would power fairy light from LiPo battery if power is not available and switch to grid power when it is back up(also to charge LiPo battery).

Resistor R51 is optional and 100Ohm value selected based on fairy lights sting I using. You can jump it if you doin't need current limiting or choose another value based on your target use.

R52 is a through hole footprint for connecting potentiometer and/or switch to fine-tune output voltage/turn-off output.

Ecnlosure can be found here: https://www.pcbway.com/project/shareproject/Enclosure_for_12V_LED_Fairy_lights_PSU_with_backup_power_source_842a3eee.html