diy 12V ups questions

[Diyaudio_enthusiast]

Good day members

I'm making a small 12V ups for routers,modems etc..
Main power supply is a 12V 2A wall power adaptor.
Secondary power supply is a single 18650 connected to tp4056+voltage boost module.
I'm planning to use IRF9530N p channel mosfet for switching.
I've attached a rough schematic to show the connection.
Please let me know about possible issues with this arrangement.
Thanks

[Vovk_Z]

Why do you need a switch?

[Diyaudio_enthusiast]

Why do you need a switch?

to switch between wall adaptor & battery (when mains power down)

[ogden]

You can buy that thing instead:

https://www.meanwell-web.com/en-gb/ac-dc-industrial-din-rail-with-ups-function-output-drc--40a

[Vovk_Z]

The switch can be eliminated choosing the right voltage for the charger.
Doy you reaaly need to switch between them if you have protective Shottky (or other type) diodes?

[JohanH]

I've had a stupid charger/powersupply adjusted to 13 V connected to a small 12V lead battery for 6 years now, driving router, wifi access point, network switch, modem and a raspberry pi (using a 12V to 5V DC converter) for 6 years. Foolproof and no circuitry needed.

[Vovk_Z]

I'm talking about the same.

[Diyaudio_enthusiast]

Thanks all for the input
Mains supply is quite unstable here.
When there is repair, we wont be having any power for 8 hours.
I'm using this as a learning experience too.

[HB9EVI]

like the others said, the easiest way is to build an adjustable power supply, set it on ~13-13,8V (which is no problem for common 12V devices) and hold a Pb battery in parallel on float charge.

Calculate the current drain from your devices and choose an appropriate Ah rated Pb-battery and you're fine to go also for longer than 8h