I made a portable charger thaat has a USB port for any charging source
Battery snap connector
Power switch with wires
Hot glue or tape
Step 1: Wiring
Get Battery snap connector. Connect snap connector to battery. Solder positive end of snap connector to to negative end of the power switch. Connect negative end of snap connector to car charger using electrical tape. Connect negative end of power switch to side of car charger also using electrical tape.
Step 2: Boxing
Use a box made of cardboard or plastic. Cut one rectangular whole in the bottom corner of the box. Cut a small circular whole in the side wall of the box for the power switch.
Step 3: Placement
Electrically tape car charger to bottom corner hole so that USB port is sticking through the whole. Have battery in open area to be replaced. Poke power switch through small circular hole.
Step 4: Add Top of Box
Place top of box on to close in wiring using either hot glue or tape.