I am currently working on a DIY project, and I am using a Raspberry Pi 5 as the central brain of my system (I do not have them now but I am thinking at some point to add the HAT AI module and some SSD Storage to give an idea of the power usage and intensity requirement). I would like to put in place a DIY UPS system that would allow the raspberry Pi5 to shutdown properly in the case of system power cut detection. My power input is coming from the main power supply of my system with a step-down converter from 12V to 5V (DC-DC Converter XL4016). I made some research on readily available system on the market but found them expensive, over spec or hard to integrate in my overall system. I came up with the following proposal, as I am unexperienced in electronic I would like to seek for some advice or correction, improvements and optimization ideas

Here are the components list:
Components | Details | Link |
---|---|---|
Battery charger module | TP4506 | Amazon |
Battery holder | 2x slots 18650, parallel wiring | Amazon |
2x Battery | 18650 ≥2600mAh | |
Battery protection board | 1S 3.7V – Min 5A for spike if possible | Amazon |
Boost converter | MP3429 | Aliexpress |
Schottky Diode | 1N5820 / 1N5822 | Amazon |
Resistance | 100kΩ | Amazon |
Zener diode | 1N4728A – 3.3V | Amazon |
Ceramic capacitor | 0.1μF | Amazon |
Analog to Digital Convertor (ADC) | ADS1115 | Amazon |
* Links for reference only
Thank you in advance for any comments