ZDNET’s key takeaways
- A USB-C power bank and a trigger cable can keep a router running during an outage.
- Your power bank needs to support 12V output, or you’ll need a cable with a step-down converter.
- Do a test run while the power is still on by following the steps below.
Storms, cold snaps, unexpected grid failures, and the risk of cyberattacks mean many of us will experience a power outage at some point.
Also: The best power banks: Expert and lab tested
When you live in a rural area with intermittent, patchy, or non-existent cellular coverage, losing your home internet access without warning can prevent you from contacting family and friends, reaching emergency services, maintaining your normal routine, or working.
However, with the right preparation, you can create an inexpensive backup system to keep your home router and internet running a little longer.
While a portable backup generator or Uninterruptible Power Supply (UPS) device is great to have, a DIY approach can use the power bank — the one stashed away in your home office for travel — to keep you connected until the power comes back on.
Will powering my router keep me online during an outage?
Power failures happen for a reason. Extreme weather events and storms can knock out power lines and damage telecom services and junction boxes. While your internet service provider (ISP) usually has backup power at its own facilities, there’s not much you can do if an outage cuts the connection between the ISP’s service and your home.
It’s also important to know the difference between a home power outage and a service interruption at your ISP. You can restore power and keep your router going, but if there’s an outage at your ISP, you still won’t be able to get online.
Also: The best home portable power stations
So if your internet goes down, the first thing to do is grab your smartphone and check whether your ISP is having issues in your area.
What about Starlink?
Many rural homes rely on Starlink, a satellite-based internet service provided by SpaceX that targets consumers who have little to no existing broadband coverage, including in rural and remote areas.
A standard power bank probably won’t be enough to keep Starlink running, since it needs more power than the average router and modem setup, and you’ll likely need to invest in a portable power station or generator.
Also: How I turned my Starlink Mini into the ultimate off-grid internet device
However, the Starlink Mini needs less, and so a reasonably powerful backup battery or power bank will likely suffice. Dedicated Starlink Mini power banks are also available online.
What a power bank can and can’t do
Power banks vary in size and battery capacity, measured in mAh (milliampere-hours) and, more usefully, in watt-hours (Wh).
Some energy is always lost as heat during conversion, so — as Anker notes — a power bank typically provides around 60% to 75% of its rated mAh as usable output.
Also: I’ve owned 50+ portable power stations – one number matters most
Many of us overestimate how much a power bank can deliver during an outage by looking at the mAh rating rather than the power we can realistically expect. A typical 10,000mAh power bank might charge your smartphone once or twice, while larger power banks with higher mAh ratings and dedicated fast chargers may keep your laptop going for several hours.
They won’t, however, power larger, AC-powered appliances such as your refrigerator, and you should seek a specialist’s assistance for backups intended to keep medical devices running during a power outage.
How does a power bank run a router?
Your router’s power adapter takes AC from the wall and converts it to low-voltage DC, usually 12V. Instead, we need to safely recreate this supply at the right voltage level from a power bank.
We do this with a power bank that supports Power Delivery (PD) over USB-C and a trigger cable that can switch the power bank’s default 5V to a higher voltage, which then powers your router through a barrel plug.
Search online for a 12v trigger cable. If you’re not sure what voltage your router requires, type your router’s name and “voltage” into a search engine. Keep in mind that trigger cables don’t generate voltage, so if your power bank can’t supply 12V, the cable won’t work.
What gear do I need?
- A power bank: The higher the capacity, the better. It needs a USB-C PD port that lists 12V among its outputs or a dedicated 12V DC output. The majority of ZDNET’s favorite power banks will do the job.
- 12V trigger cable: Use one with the correct barrel for your router, or a higher voltage cable with a step-down converter.
- DC splitter: You may need one if a single 12V output has to run two devices
- Power/voltage measuring device: Optional but highly recommended, this device is used to check output and reduce the risk of causing electrical damage.
Your existing router setup and Ethernet cables can stay where they are.
How to set up your power bank rig
1. Check voltage and wattage
First, check your router’s voltage. As a home networking device, it’s likely 12V. You’ll find this information on a sticker, either underneath your router or on its side. If it’s not there, check your router’s power adapter.
The router I used for this guide requires 12 volts (3A), and I found this information on a sticker underneath it, which also listed the make, model, and default credentials.
It’s also important to know how much power (or consumption) you can expect from your router, since your power bank needs to keep up.
As a rough rule of thumb, voltage (V) x amperage (A) = maximum power capacity (watts); in my router’s case, that’s 36 watts. However, this is the maximum ceiling, so it draws less during normal use because the maximum wattage includes a safety buffer.
According to independent tests on my router model, its actual power draw is between 13.5 and 15.5 watts. You can search online for accurate figures. Alternatively, you can use a plug-in or USB-C power-measuring device to record day-to-day draw rates in advance.
2. Charge your power bank
You don’t need a huge power bank to make this work, but the larger the battery capacity, the better, since it will power your devices longer.
Next, check which voltages your power bank can output. For example, if your power bank defaults to 5V (as mine does), we will need to create 12V, the rate my router needs. Look for optional outputs on the casing or in the guide, such as 9V or 12V. If 12V is missing, unfortunately, your power bank won’t be suitable for devices that run on 12V, including many home routers.
Ensure your power bank is fully charged, and top it up every so often. Power outages don’t tend to announce themselves in advance, and a power bank with 20% remaining is no good to anyone during a blackout.
3. Purchase a suitable trigger cable
When you buy your trigger cable, the easiest thing to get wrong is choosing the wrong barrel tip. My router uses a standard 5.5mm x 2.1mm barrel plug. If you’re unsure, the easiest way to find out is to search for “router name, model, plug.”
I picked up a 12V (3A) 36-watt cable. Keep in mind that the cable’s rating doesn’t add power, since your power bank’s 12V output is the real limit.
If you need to run two devices off your power bank, such as your router and a fiber ONT or separate modem, you’ll also need a splitter. A splitter shares one port’s output between both devices, so add their power draw together and check the total against what your power bank can supply at 12V.
12V isn’t supported by every PD power bank, so check which voltages yours is compatible with. A trigger cable that requests 15V or 20V and has a built-in step-down converter that outputs 12V could work, but be careful: a standard 15V or 20V cable without a step-down converter could fry your router.
4. Test and assemble your rig
With your power bank charged and your cables ready, switch off and unplug your router and, if it’s a separate device, your modem.
Before connecting anything to your router, however, plug the trigger cable into your power bank and check the output at the barrel end with your power meter. You want to see around 12V, and if you see anything else — like 5V or 15V — it’s safest not to continue with that cable and power bank.
Plug the USB-C end of your trigger cable into your power bank’s USB-C PD port. Give it a few seconds to negotiate the right voltage, then push the barrel plug into the router’s power socket. If your modem is a separate box, repeat this with a second cable and a free PD port, splitter, or with a second power bank.
You don’t need to touch your Ethernet or coax cables.
5. Wait for your router to reboot
If your router is anything like mine, it will take around 4 to 5 minutes to boot and reconnect. In my case, the light flashes green once it’s online, and red when it’s struggling to connect. Be patient before deciding your setup has failed, as it took mine a minute or two longer than usual to resume normal service.
6. Check you’re online
You can now check to see whether your internet access has been restored.
At this point, be patient before deciding your kit has failed. You can also run a speed test, such as the one found at speedtest.net, to make sure everything is working normally.
7. Keep an eye on your battery
Once you’re online, keep an eye on your power bank and battery capacity. If it has one, check the battery display on the screen; alternatively, you may be able to see the remaining percentage by pressing the power button.
How long will my router stay on?
We suggest a trial run while you have power, but you can also use your power bank’s rating to roughly estimate how long you may have internet access during an outage.
First, convert mAh to watt-hours: multiply the mAh rating by 3.7V (the nominal voltage of the lithium-ion cells inside), then divide by 1,000. Many power banks also print a Wh figure on the label; if yours does, use that instead.
So, my 26,800mAh power bank equates to about 99 watt-hours.
Assuming around 30% is lost to conversion, that leaves about 69 usable watt-hours (99 x 0.70).
Next, divide that by your hardware’s power draw. At my router’s idle draw of 13.5 watts, that’s about five hours. Under heavier use at 15.5 watts, it’s closer to 4.5 hours.
During my test, my power bank kept me online for about two hours and 20 minutes. It’s not all day, and it’s below the estimates, but it’s far better than nothing in a power outage.
Problems you might encounter
There’s no cut-and-dried answer to how long your modem and router will stay on when you’re relying on a power bank and a cable or two.
To set this system up, you will need to check, and double-check, that you have the right kit — it’s easy to purchase a cable with the wrong tip or barrel. This goes for voltage, too, as rigging up a kit with the wrong voltage in mind could cause electrical damage.
As I found with my test power bank, it won’t act like a UPS. When you build your own, keep in mind it is an inexpensive alternative to a UPS that won’t automatically switch over during a sudden power blackout. As a result, you will have to wait for your router to reboot to restore your connection.
If you keep your power bank connected at all times, you also risk wearing down its battery, reducing its capacity and increasing the risk of failure.
Other options to keep your internet on during a power outage
A power bank and cable rig is not your only option to keep your internet on during a power outage. Other options include:
- Portable power stations: Portable power stations from companies including Jackery and EcoFlow are one of the most reliable ways to keep the lights on during a power outage, but they are a significant investment.
- UPS devices: Uninterruptible power supply devices are ideal for keeping hardware, including routers, on during an outage, as they switch over as soon as a power failure is detected. They come in a range of sizes, capacities, and voltages.
- Mini DC UPS devices: You can pick up smaller, cheaper UPS devices produced especially for routers. While limited in power, they can keep you online without requiring a DIY solution.
- Solar power: If you have solar panels and battery storage, a solar rig may see you through the worst of a power blackout under the right conditions.
- Mobile cellular dongles and hotspots: A mobile dongle or smartphone hotspot with 4G or 5G connectivity can work in some cases.
- Generators: An expensive but solid option, especially for those in rural areas, a home generator can keep power flowing even if the grid is experiencing disruption.
How to prepare for the next outage
Power blackouts rarely come with a warning and countdown timer, so being prepared now can give you peace of mind that you can stay connected, even if one occurs at the most inconvenient moment.
We recommend taking half an hour to audit your devices, check whether you have a spare power bank or two, and jot down the power ratings and needs of the devices you will want to keep running most during a power outage.
Also: The best home battery and backup systems: Expert tested
At this stage, we also recommend comparing your power bank’s capacity with the needs of your router and other crucial devices, then ordering the kit you need.
Ideally, do a trial run with a battery backup for your internet connection. Once you know how long you will stay online, you can decide whether the power bank you’ve scavenged from your office and a few cables are enough, or whether you need a UPS or portable power station.