5 volt small UPS design (review request)

Question

I'm designing small 5 volts UPS that would allow me to run on battery or 5V source.

If source is unavailable, step-up module takes power from battery.
If this 5V source is restored, then this source is taken for step-up module, but also battery is being charged

There are two diodes, so only one source will be taken to step-up module, by comparing voltages - 5V or from battery (3.7-4.2V),

I've decided to do it semi-DYI, so I used some ready made components,
but I'd like You to review these connections.

Connection and modules in short:

• charger module is a widely available TP4056 module, available for few bucks. It stops charging at 4.22V and resumes charging when battery voltage below 2.8V
• Li-ion battery is a 18650, 3.7V one, scrapped from battery bank (no protection)
• two diodes shown on image below are Schottky 1N5819 1A / 40V
• at the output, I have step-up module that gives me a stable 5V/500mA source for devices connected

Is this module safe to leave it unattended, or maybe you would change something here, like adding extra protection, modules replacement ? I used Schottky diodes, but since this is my first real electronic project (without the ones did for a fun and learn), I didn't want to complicate this design with PNP/NPN transistors. I need to know them more, or learn all theirs weaknesses first.

Answer 1

The TP4056 module is good for charging but it's quite possible the step up module has a 20mAh or so quiescent current and it might drain the battery even when it's not powering something. If you're not using this for a very low power device then it might not matter.

In my opinion, a better option would be to use something based on TPS61090 such as the PowerBoost board.

Otherwise your concept it's clearly cheaper if that is more important here.