18650 2P piggyback case with charger

Update 02/2022: V2 design added. Its now taller but without wide part for the charging board, which now sits in the bottom. Intended for usb-c charging board with protection:
https://www.aliexpress.com/item/32971075877.html (make sure to select usb-c version)
You will have to round the corners with a file/dremel/some cutters
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So when the battery in the babyphone died I did not want to replace it with the expensive proprietary battery that had way to small capacity and I designed this part.

It houses 2 18650 cells connected in parallel and a small charging + protection circuit with usb connector

2 parts have to be glued together and the charger board has to be glued in as well. I used transparent epoxy for this, since it allows the charging status leds to shine through the hole.

I would not advise to use glue gun since the charging boards can be quite warm when charging cells from empty state

Please make the hole for the wires in desired location of the bottom plate, since it can differ from device to device.
Can be attached with decent double sided foam pad to the device

micro usb and usb-c versions available

I used following charging board:
https://aliexpress.com/item/33014407576.html