Sometimes we have power outages that last about 100 ms that are long enough to discharge capacitors inside router, when that happens we need to wait about 10-15 minutes for DNS, which is pretty annoying. What I'd like to do is have (cheap) UPS only for the router that will withstand 0.5 s power outages. Router specs (I will test them with a multimeter to be sure about amperage) are 12V 1.5A. I think my options are:
SLA battery with a charger and DC boost converter, 4V 4.5Ah (smallest one I can get). I searched for 4V SLA chargers but I can't find any, I would need to make one from standard 12V switching power supply via timing circuit and step down converter. I would need to make further research about charging SLAs.
Capacitors / supercaps. Adding electrolytic caps in parallel between DC barrel jack. Don't know the viability of this solution. Would need to research how to calculate appropriate capacitance.
The solution with capacitors would be much simpler.
Edit: after doing some more research I came up with this setup:
2 × 18650 batteries connected to 2S PCM circuit 2S 5A PCM that go through boost buck converter to give 12V (also with 2S battery indicator). Not sure how to make it only work when there is no power so that the wall wart is still connected. Only minus is that after few discharges/long use time I would need to recharge the batteries, but that won't be a problem.