This is an 18650 'adapter' for 4-gang Zigbee wall buttons.  These button units run off a single CR2430 coin cell battery…for about 2-3 weeks at a time.  They just murder batteries.  This adapter allows them to be run off a much larger, and rechargeable, a 18650 cell.

The adapter fits between the original wall attachment plate and the switch assembly itself.  (I had already attached the switch's original wall plates to my walls and didn't want to disturb them.)  The 18650 battery is accessed through the back, by sliding the adapter+switch off the wall.  The switch can be installed on the adapter once and then left there.  There is a goofy little CR2430 adapter included.  I just stripped the wires from the 18650 holder a little longer and ran them through the CR2430 adapter.  Line up the + wire with one of the spring clips on the original CR2430 holder as you insert it.  Make sure to get the polarity right!  I don't know if these switch units can survive reverse voltage.

I think all the 4-gang button units are roughly the same.  Some of them are Tuya branded, others just don't have a brand.

I've used this model with these two from amazon:

• https://www.amazon.com/gp/product/B099KDS3W9
• https://www.amazon.com/gp/product/B09SPG28KP

Those two have slightly different, though clearly very related, mounting brackets.  The white one has a plastic spring latch mechanism that the black one lacks.  The original wall plates are thus not completely compatible.  But this model doesn't use that latch and so is compatible with both.

I used these battery holders:

• https://www.amazon.com/gp/product/B0BJV7SK5D

Sadly the model needs supports.

I've included the (poorly written) OpenScad model.

I took inspiration from two existing models:

• https://www.printables.com/model/746494-tuya-4-gang-zigbee-18650-upgrade
• https://www.printables.com/model/296184-smart-switch-4gang-tuya-cover-and-base