Backup psu for router - Page 1
Forum section: electronics / general

author: thyristor44
author_rank: Newbie
timestamp: October 07, 2025, 12:19:42 pm
content: HelloAfter a power cut for a few hours I would like to buy or make a backup supply. My router takes 12v ay 0.8a and sometimes I have been off for 6 days.The phone is voip so no phone and the phone network also goes down so no emergency.I thought on the idea of 100ah lithium battery but not sure about charging and automatic operation so any help would be appreciated.Thanksthyristor44

author: rteodor
author_rank: Frequent Contributor
timestamp: October 07, 2025, 01:03:33 pm
content: Most, maybe all routers would take in without any problems higher voltage. I powered a few such routers (one rated 7.5V and another rated at 9V) without problems from 12V VLRA batteries for a few months. But because I also have other stuff (like HDD) I settled to powering everything via a MeanWell RSD-60G-12 DC/DC converter. It takes any 9 to 36V input and outputs 12V.You could try to power the router directly from the battery if you are brave or use such a converter. Then you need only a suitable charger. And a BMS for the battery if one isn't already in there.

author: thyristor44
author_rank: Newbie
timestamp: October 07, 2025, 02:12:13 pm
content: Quote from: rteodor on October 07, 2025, 01:03:33 pmThanks rteodor but what is a BMS

author: rteodor
author_rank: Frequent Contributor
timestamp: October 07, 2025, 04:08:42 pm
content: Quote from: thyristor44 on October 07, 2025, 02:12:13 pmBattery Management System. At the most basic it's a switch in series with the battery and some ADC measuring each cell with the purpose of protecting the battery against over-charge or over-discharge. Most often these days a BMS is also a shunt measuring state of charge (SoC), a balancer and and sometimes there is some Bluetooth interface for a smartphone app so you can check the battery. That is what you will most likely get if you get one of those LFP (LiFePO) batteries all packaged in a single case.As for the charger it depends on what type and capacity of battery you get and how fast you need it recharged. In the most simple case, with LFP you could use a power supply set to 13.6V (floating at 3.4V / cell) and leave it always connected. Not the ideal way to do it but it will work.

author: thyristor44
author_rank: Newbie
timestamp: October 07, 2025, 04:58:46 pm
content: The router is 12v and the battery I am thinking of is 12v lithium 100AH should give me about a week backup.I can get an auto swich for if power goes down. Next thing to look at is a battery charger.

author: rteodor
author_rank: Frequent Contributor
timestamp: October 07, 2025, 05:16:52 pm
content: Quote from: thyristor44 on October 07, 2025, 04:58:46 pmIf you look for a charger then look for one that can charge the exact type of Li chemistry battery you will have. LFP would be the most appropriate nowdays. In any case pay attention to this detail.As for the auto switch it could be as easy as two diodes. In this case you will need a power supply that has at least about 0.5...1V more than the maximum voltage of the battery so not to drain energy from the battery while the router is supposed to be powered from the power grid.

author: Someone
author_rank: Super Contributor
timestamp: October 07, 2025, 10:28:22 pm
content: Quote from: thyristor44 on October 07, 2025, 02:12:13 pmRather than building your own system it would probably be quicker/cheaper/easier to buy a "portable power station" (or whatever other stupid name a company picks to use) that already includes all the interfaces and electronics:https://www.cnet.com/home/energy-and-utilities/best-portable-power-stations/Use DC outputs or a USB-C to barrel connector cable.

author: makebit
author_rank: Unknown
timestamp: October 16, 2025, 02:24:53 pm
content: I would get yourself a battery pack of say 6S lithium.Drop a divider off each cell top.Then when discharging, whenever any cell gets to 3.5V, stop discharging the battery. Have a comparator to stop your converter from working when any cell goes down to 3.5V.For the converter....download free kicad, get yourself a nice easy SEPIC design with cheap UCC28C45. Two uncoupled inductors....12V 0.8AFor the charger, use what you like and just remember, stop charging soon as any cell gets up to 4.2V. So get your comparator circuits back in there and shut off charging when any cell is >4.2V.Again.....the free kicad and lay out a nice ucc28c43 current regulated boost SMPS from say a 12V meanwell supply to your battery.For the SEPIC...if you want more capacity....just have more charged 6S batterys and swap 'em in when your first battery goes flat.

author: coromonadalix
author_rank: Super Contributor
timestamp: October 16, 2025, 02:42:43 pm
content: not sure if that thing can helphttps://www.ebay.ca/itm/315550939393?https://www.ebay.ca/itm/405347370566?