How to make a 9V battery with USB charging

9V batteries are not often used, but are still used in various toys, radios, and measuring instruments. Their resource is not very durable. In order not to constantly buy these batteries, you can make such a battery yourself with USB charging. Everything is made from a ready-made module and a lithium battery.

Will need

Old crown.
Mini switch.
Charging converter module -
Lithium battery 3.7 V -

How to make a Krona type battery with charging from 5 V

Remove the braid from the old battery.

We carefully open the case using a sharp scalpel.

We recycle the insides. We need the plastic case itself with the block.

We mark the housing for the board connector.

We cut out the window: first we burn it with a soldering iron, then we shape it with a sharp scalpel.

Solder the wires to the board. It has all the symbols. We solder the output of the converter directly to the block, and solder the contacts from the battery to the battery only through a switch.

We check the operation with a multimeter. When the switch is on, 9 Volts should come out at the block.

We glue the light guide to the LEDs on the board with super glue.

We glue the board into the case.

In the block we make a cutout for the switch and a hole for the light guide. Glue in the switch.

Glue the block to the body. We bite off the light guide.

Our 9V Krona battery is ready.

Can be put on charge.

Red Light-emitting diode lights up when charging is in progress, green when charging is complete.
Now you can check it in practice.

The switch serves to disconnect the converter from the battery, since it consumes little current even in idle mode. And if the device where the battery is installed is idle for a long time, it must be turned off.