To safely hold the lipo battery, we'll create a simple pocket on the back side of the tie.
This pocket will be attached to the tie using heat-activated hem tape, but you could easily recreate it using traditional sewing if you prefer.
Cut a piece of fabric 60mm x 75mm in size.
Cut 4 strips of hem tape; 2 x 75mm, & 2 x 15mm
Arrange the pieces of hem tape in the shape of the pocket near the bottom of the tie’s back seam. Leave a gap in the middle of the pocket's bottom to allow the battery's wiring to pass through.
Carefully place the pocket fabric on top of the hem tape. Make sure the tape is at the outer edges of the pocket – you won't be able to reposition it after ironing.
Gently place a piece of scrap fabric over everything to protect the pocket fabric while ironing.
Apply firm pressure with a hot iron for 10 to 20 seconds. Move the iron back and forth to fix the pocket evenly in place.
Once you’re done, check to make sure the pocket is fully adhered to the tie.