Introducing Pi-Vault a zero sized but fully capable DC UPS and PSU for RPi of any size!
Pi-Vault is designed by myself and uses firmware developed by J.Baumann based on this Attiny-Daemon
https://github.com/jbaumann/attiny_daemon and tailored to Pi-Vault.
You can power Pi-Vault by USB-C (5V3A max) which is not recommended for Pi with more than 2A of current requirements (2A for Pi, 1A for battery charger), It is absolutely fine for Pi zero or zero W or less demanding applications. (limitation applies only while battery is charging)
You can also power Pi-Vault from its DC input with ANYTHING that can supply DC Voltage between 8 and 28V. Power source must be able to supply at least 20W of power... There is input reverse polarity protection and disconnect switch. Can be used with 12V solar panels.
Battery charger will work with 1S Li-Ion/LiPO battery charging at 1A max.
Battery must be able to supply at least 8A (using 2-3 cells in parallel will help with weaker cells).
Battery protection allows handling high currents up to 10A.
Output is capable to deliver 5V3A recommended for RPi and can even reach 4A for short durations without problems but airflow/cooling is required to sustain power above 15W for prolonged periods of time.
Pi-Vault uses an attiny1606 to handle communication with its host Pi over I2C.
There is an addressable rgb led for status indications and a pushbutton to turn system on/off (can use external switch too).
A DS1307 RTC with optional backup battery is also present.
I will place order for pcb/components for an initial small batch which is available as early bird at a lower price.. in about 3 months from now Pi-Vault will be available on groupgets.com and later on on tindie.
If interested on early bird, please send a private message
To answer common questions
I use easyeda for my designs
Design will eventually be open sourced but please do not ask for schematics for few more months.