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Will It Work? · Guide

Keeping Wi-Fi on in a power cut: router, fibre box and a battery

By Bulan Sarkar, founder of ElectronicsInfoline (since 2000)

A home fibre connection needs two boxes powered: the fibre box (ONT) where the line comes in, and the Wi-Fi router. Both run from small DC adapters, which makes them easy to keep on a battery through a power cut or outage. This works through the three steps with the makers' own figures.

Read the OUTPUT line on both adapters, add up volts × amps, and choose a battery with at least that many watts × the hours you need, plus the converter's loss. Example from maker spec pages: a 7.65 W router and a 5.4 W fibre box draw at most 13.05 W, so 4 hours needs more than 52.2 Wh of battery.

Step 1: find the watts

Each adapter's OUTPUT line gives volts and amps; multiplied, that is the most the device can draw.

Reading the output line on an adapter labelAn example adapter label. The OUTPUT line reads 9 V and 0.85 A; multiplied, 7.65 W is the most the device can draw through it.SWITCHING ADAPTERINPUT: 100-240V~ 50/60HzOUTPUT: 9.0V ⎓ 0.8A⊖-◐-⊕ centre positive9 V × 0.85 A= 7.65 Wthe mostit can drawINPUT is the wall side. Only OUTPUT matters here.
Figure 1. Read the OUTPUT line, not INPUT. Volts × amps gives the most the device can draw through that adapter: 9 V × 0.85 A = 7.65 W. Example label; yours will differ.

Figures from makers' own spec pages (India and US models listed separately; the same name can be a different model):

ModelMarketMaker's figure
TP-Link Archer C6 (TP-Link)Indiaadapter 12 V × 1 A = 12 W (most it can draw)
TP-Link Archer C64 (TP-Link)Indiaadapter 12 V × 1 A = 12 W (most it can draw)
TP-Link Archer AX10 (TP-Link)Indiaadapter 12 V × 1 A = 12 W (most it can draw)
TP-Link Archer AX23 (TP-Link)Indiaadapter 12 V × 1.5 A = 18 W (most it can draw)
TP-Link Archer C50 (TP-Link)Indiaadapter 9 V × 0.85 A = 7.65 W (most it can draw)
TP-Link Archer AX55 (TP-Link)USadapter 12 V × 2 A = 24 W (most it can draw)
TP-Link Archer AX21 (TP-Link)USadapter 12 V × 1.5 A = 18 W (most it can draw)
TP-Link Archer AX3000 (TP-Link)USadapter 12 V × 1.5 A = 18 W (most it can draw)
TP-Link Archer A8 (TP-Link)USadapter 12 V × 1.5 A = 18 W (most it can draw)
NETGEAR RAX10 (Nighthawk AX4) (NETGEAR)USadapter 12 V × 1.5 A = 18 W (most it can draw)
NETGEAR RAX50 (Nighthawk AX6) (NETGEAR)USadapter 12 V × 2.5 A = 30 W (most it can draw)
NETGEAR R7000 (Nighthawk AC1900) (NETGEAR)USadapter 12 V × 3.5 A = 42 W (most it can draw)
ASUS RT-AX1800S (ASUS)USadapter 12 V × 1.5 A = 18 W (most it can draw)
TP-Link XN020-G3 (GPON/XPON ONT router) (TP-Link)Indiaadapter 12 V × 0.6 A = 7.2 W (most it can draw)
TP-Link XC220-G3v (XPON ONT router) (TP-Link)Indiaadapter 12 V × 1 A = 12 W (most it can draw)
TP-Link XX230v (GPON ONT router) (TP-Link)Indiaadapter 12 V × 1.5 A = 18 W (most it can draw)
TP-Link XZ000-G3 (1-port GPON terminal) (TP-Link)Indiaadapter 9 V × 0.6 A = 5.4 W (most it can draw)
Huawei EchoLife EG8145V5 (GPON ONT) (Huawei)globalmaker: maximum 12 W

Step 2: size the battery

Battery Wh needed = watts × hours ÷ efficiency. With 13.05 W, every hour takes 13.05 Wh before losses. The curve shows hours against load for a battery that delivers 50 Wh after losses:

Runtime against load for 50 Wh of usable energyHours = 50 Wh ÷ watts. At 5 W: 10 h; 10 W: 5 h; 20 W: 2 h 30 min; 40 W: 1 h 15 min. Marked: 13.05 W gives 3 h 50 min.5 W10 h10 W5 h20 W2 h 30 min40 W1 h 15 minhoursload
Figure 2. Runtime falls as the load grows: double the watts, half the hours. Curve for 50 Wh of usable energy.

At 13.05 W, 50 Wh lasts 3 h 50 min. The power-cut backup calculator does this for your own devices and battery, and works out the efficiency from a power bank's rated-capacity line.

Step 3: connect on the low-voltage side

The battery unit takes the place of each adapter. Each output has to match the voltage on that device's adapter label, and the plug has to fit with the same polarity. Nothing in this setup touches the mains wiring.

A DC mini-UPS or power bank feeding the router, fibre box and phoneThe battery unit has a 9 V output to the router, a 9 V output to the fibre box and a USB output for the phone. Each output voltage must match the device's own adapter label.Battery unitpower bank orDC mini-UPSWh on the label9 V DCWi-Fi router9 V DCFibre box (ONT)USB 5 VPhone
Figure 3. Low-voltage side only: the battery unit replaces each device's adapter. Match each output to the voltage on that device's own adapter label, and check the plug size and polarity.

Tips and tricks

  • Photograph both adapter labels before you shop. The voltage, current and plug matter more than the brand.
  • Some fibre boxes and routers use different voltages. Count the outputs you need at each voltage.
  • A phone hotspot is the other backup: it needs no extra box, but uses mobile data and the phone’s battery.
  • Check your fibre box’s own label rather than a list: providers supply many models, and the same name can be a different unit.

What we would do

Add the two adapter ratings, multiply by your usual cut, and pick a DC mini-UPS or power bank with outputs at both voltages and enough Wh after its losses. If the maker gives no efficiency or rated capacity, size up rather than down, since the calculator's ceiling assumes no losses at all.

Questions people ask

How much power does a Wi-Fi router use? The adapter label sets the ceiling. The makers’ own spec pages give, for example, TP-Link Archer C50: adapter 9 V × 0.85 A = 7.65 W (most it can draw); and for a fibre box, TP-Link XZ000-G3 (1-port GPON terminal): adapter 9 V × 0.6 A = 5.4 W (most it can draw). Real use can only be the same or lower.

What size of battery keeps Wi-Fi on for 4 hours? Multiply the total watts by 4 and divide by the converter efficiency. A 7.65 W router and a 5.4 W fibre box (adapter ratings) need 52.2 Wh even at 100 % efficiency, and more for real losses.

Do the router and the fibre box both need battery power? Yes. The fibre box brings the internet in and the router shares it. With either one off, the Wi-Fi has no internet.

Sources

Each figure on this page is quoted from the source below or worked out from them. Sources checked , each quote read again against the source in a second pass.

  1. TP-Link, TP-Link Archer C6: Power 12 V ⎓ 1 A tp-link.com/in/home-networking/wifi-router/archer-c6/
  2. TP-Link, TP-Link Archer C64: Power 12V = 1A tp-link.com/in/home-networking/wifi-router/archer-c64/
  3. TP-Link, TP-Link Archer AX10: Power 12 V ⎓ 1 A tp-link.com/in/home-networking/wifi-router/archer-ax10/
  4. TP-Link, TP-Link Archer AX23: Power 12 V ⎓ 1.5 A tp-link.com/in/home-networking/wifi-router/archer-ax23/
  5. TP-Link, TP-Link Archer C50: Power 9 V ⎓ 0.85 A tp-link.com/in/home-networking/wifi-router/archer-c50/
  6. TP-Link, TP-Link Archer AX55: Power 12 V ⎓ 2 A tp-link.com/us/home-networking/wifi-router/archer-ax55/
  7. TP-Link, TP-Link Archer AX21: Power 12 V ⎓ 1.5 A tp-link.com/us/home-networking/wifi-router/archer-ax21/
  8. TP-Link, TP-Link Archer AX3000: Power 12 V ⎓ 1.5 A tp-link.com/us/home-networking/wifi-router/archer-ax3000/
  9. TP-Link, TP-Link Archer A8: Power US Version: 12 V ⎓ 1.5 A EU Version: 12 V ⎓ 1 A tp-link.com/us/home-networking/wifi-router/archer-a8/
  10. NETGEAR, NETGEAR RAX10 (Nighthawk AX4): RAX10 12V 1.5A kb.netgear.com/23003/How-much-power-does-my-NETGEAR-router-u…
  11. NETGEAR, NETGEAR RAX50 (Nighthawk AX6): RAX50 12V 2.5A kb.netgear.com/23003/How-much-power-does-my-NETGEAR-router-u…
  12. NETGEAR, NETGEAR R7000 (Nighthawk AC1900): R7000 12V 3.5A kb.netgear.com/23003/How-much-power-does-my-NETGEAR-router-u…
  13. ASUS, ASUS RT-AX1800S: Power Supply AC Input : 100V~240V(50~60Hz) DC Output : 12 V with max. 1.5A current asus.com/us/networking-iot-servers/wifi-routers/asus-wifi-ro…
  14. TP-Link, TP-Link XN020-G3 (GPON/XPON ONT router): External Power Supply 12V/0.6A tp-link.com/in/service-provider/gpon/xn020-g3/
  15. TP-Link, TP-Link XC220-G3v (XPON ONT router): External Power Supply 12V/1.0A tp-link.com/in/service-provider/gpon/xc220-g3v/
  16. TP-Link, TP-Link XX230v (GPON ONT router): External Power Supply 12V/1.5A tp-link.com/in/service-provider/gpon/xx230v/
  17. TP-Link, TP-Link XZ000-G3 (1-port GPON terminal): External Power Supply 9VDC/0.6A tp-link.com/in/service-provider/gpon/xz000-g3/
  18. Huawei, Huawei EchoLife EG8145V5 (GPON ONT): System power supply 12 V DC, 1.5 A Static power consumption 5 W Maximum power consumption 12 W e.huawei.com/eu/products/optical-terminal/echolife-eg8145v5

Author: Bulan Sarkar · Report an error

Numbers here are quoted from standards bodies and makers, or worked out from them. Nothing on this page was measured or tested by us.