I am currently making a router backup supply as stated in the title, i just wanted to run this through you people so I don't accidentally burn down the house.. you know, i case i missed anything :o
The basic is simple. I have 13 18650 batteries connected in parallel ( ofc scavenged batteries, but tested and curated of bad cells) as a simple enough battery pack. The 2 things i need to drive is First, The Optical Network Unit, ONU and second the wifi router itself. The router needs 5 Volts 500 mA , pretty harmless, and the ONU needs 12V and 1A, although it never uses more than 10 watts.
I have a separate and dedicated 10-watt charging unit for the battery WITH 5V 2A Output, scavenged from a power Bank, The router is going to be powered by those ports.
The attiny45 is going to control the logic level MOSFET in A boost converter configuration to provide 12V, which will then be fed directly to the ONU.
The attiny will also measure the voltage of the battery pack and stop driving the boost converter circuit when the voltage drops to 3 Volts.
The system will start as soon as a power outage occurs by using a relay in NO or NC ( haven't decided yet) config, meaning the relay stays On/off when there is power. I might even use another MOSFET instead of the relay.
That's it, Am i missing something? Also, Is the attiny capable of driving the MOSFET for getting 12V?
And lastly, one more thing, I am fairly limited with my inductor choice, a 470uH 200mA one, I can't find any other one near me, and the option of making one also is like throwing stones in the dark as I don't have an LCR meter to check the value,( i do have ferrite cores) . But the values i get from online calculators is nowhere near standard values and also require quite big peak current rating around 5A. What do i do about this?