Backup/Emergency Power Options
The Scenario
B4RN fibre has arrived at your property and now you are enjoying all the benefits of great broadband speeds with practically no data cap. As a consequence you have added lots of new tech to your home and cancelled your old copper landline along with the linked phone service. Perhaps you have adopted one of the VoIP options described in the Telephony section, or alternatively you've started using Wi-Fi Calling. The one thing all these Smart devices, VoIP and Wi-Fi Calling, have in common is a reliance on your router's connection to the Internet.
So, what happens when there's a mains power outage and your routers connection to the Internet stops? Do you break out the camping stove and a book, or more likely try to phone or go online to report the problem? For those with even moderate mobile coverage that's an easy task. However, for those with poor or no mobile coverage it’s not so straightforward. Then once you have contacted the power company, you may find out the power will be off for many hours. So, what can you do to protect your access to the internet and the devices that rely upon it when the power fails? read on and you'll find out.
Perhaps you already have an auto-start generator and change over switch wired into the electrical system of your house, in which case you’ve probably got every eventuality covered. For those less well prepared one possible answer is a battery-based emergency power supply. These are often referred to as an Uninterruptible Power Supply and can take many forms, at the simplest level it can just protect a single device e.g. the router, but they can be designed to support multiple devices. It's also worth knowing that B4RN already has battery backups and generator hook-up points in all their network cabinets; provided your router is powered you will be available to access their service during a power outage.
A SAFETY NOTE as with all things electrical and battery related it’s really important to source devices that meet the regulatory standards, this is still indicated through the CE mark. Purchasing recognised makes through an established UK based retailer, perhaps with a UK extended warranty, is to be recommended. Be wary of purchasing unknown brands from online marketplaces, a UPS should be designed to safely run 24/365 and you will be leaving them powered and unattended in your property. The need to follow manufacturers guidelines and specifically battery safety advice should not be underestimated.
What you should consider before investing in a UPS
When a power cut occurs how prepared do you want, or really need, to be? ask yourself the following set of questions.
What powered items/services are really essential to you in your day to day life? How much power do they consume?
How long, and how often, do power outages occur in your area?
How much are you prepared to pay to avoid the inconvenience of a power outage?
When power is restored after an outage how long does it take to get your system/equipment to be operating normally?
Are there any items you really want to protect from power surges and spikes?
Do you already have alternatives to your mains powered service/devices, e.g. Mobile Phone, Battery Powered radio
If you consider just one or two low power devices as essential then in most instances a DC UPS solution will offer the most convenient and typically more cost effective solution e.g. more minutes runtime for a given cost. If however you wish to protect multiple mains powered devices, e.g. Printer, network switch, Monitor, PC etc then an AC UPS is more likely to be a better option. Note: Laser printers have particularly high peak current ratings and a UPS has to be very carefully sized for this special use case.
Backup Power Options
Micro DC Uninterruptible Power Supplies- Expandable Section
DC Uninterruptible Power Supplies are widely used in a commercial context, but they also come in a form more suitable for the domestic or Small Office/Home Office. Micro DC Uninterruptible Power Supplies are designed to typically power between one and four small DC devices. They are connected between an external source of power e.g. Mains 240VAC and the protected device, in many cases they simply connect between the "Wall Wart" and the associated device.
They contain. a rechargeable battery pack and supply in most instances a few 10's of Watts; perfectly suitable for powering things like Routers, network switches, cameras and VOIP Analogue Telephone Adaptors. A typical Micro DC UPS costing less than £80 will power a standard domestic Router for a few hours. For a given run time Micro DC UPS are considerably smaller and cheaper than the equivalent AC UPS.
A DC UPS must be matched with the device it is directly powering, i.e. the same DC Voltage and capable of supplying sufficient power. In turn, the power input to the DC UPS must be sufficient to power both the device and the power required to recharge the UPS battery. e.g. 24 Watt Router requires a 24 Watt UPS requires a 30Watt AC/DC power supply. In normal operation the AC/DC supply powers both the UPS and the protected device. They can generally be described as an online UPS in that there is no delay in switching between the AC derived input power and the battery power.
It is important to understand the different ratings of a Micro DC UPS.
Max Output Power in Watts
DC Output Voltage, e.g. 12Volts
Input Voltage e.g. 12 Volts DC
Storage/Usable capacity WattHours, or sometimes quoted in milliAmphours*
*If the UPS capacity is quoted in mAh, then it is possible to work out the WattHours but it will depend on the battery cell technology used and how it's connected. Lead Acid batteries have a nominal 12V, so for a single battery simply multiply the figure given in mAh or Ah by12 to get the nominal Wh capacity. Lithium-Ion cells can be connected in a variety of configurations and can have different nominal voltages but as a general guide multiply the mAh quoted capacity by 3.7 .
To work out how long a DC UPS will keep a device like a router running, you need to know how many Watts of power the router typically uses and how many Watt Hours capacity the UPS has. The usable capacity of the batteries will be less than the quoted capacity and will vary depending on the cell type used , it will typically be around 60-70% for Lead acid and 80-90% for lithium-ion.
The best way of measuring the typical power usage of a particular device, is to connect it via a simple power meter/monitor plug, see Link... Note this typical power figure is not the same as the maximum rated power of the power supply, which should be used to determine maximum power that the UPS should be capable of delivering.
Example
Lithium-Ion based UPS, quoted Capacity is 36 WattHours. Router typically uses 6Watts . Nominal runtime is (36/6) * (80/100) or 4.8 Hours. The other real variable is the router's actual power consumption will vary depending on the model but also on how "busy" it is. So the nominal 6Watts demand may easily fluctuate between 4 and 12watts.
Some examples of Micro DC UPS that can supply 36 Watts
AC Uninterruptible Power Supplies - Expandable Section
Uninterruptible Power Supplies that deliver AC ( Alternating Current) power are widely used in commercial, domestic and SOHO environments. They are designed to provide power in a standard 240VAC 50Hz form and when correctly power rated are compatible with a wide variety of mains powered electronic devices. They consist of a battery pack, a battery charging circuit, a DC to AC inverter circuit and supply sensing and control circuits. In most cases an AC UPS will have multiple output sockets, thus allowing it to provide emergency standby power to many devices.
AC UPS output performance is normally quoted in a VA (VoltAmperes) figure, this is the Apparent Power and it is related to True Power measured in the more widely recognised unit of Watts; the relationship between the two measurements is referred to as the PowerFactor (PF). Power calculations in AC systems are slightly more complex than the equivalent in DC systems as capacitive and inductive loads vary the PF. For the purposes of simplicity a nominal PF of 0.8 can be used when considering an AC UPS e.g. a 800VA UPS can supply a maximum of 640Watts, some manufacturers do quote the PF for their units, it can be as low as 0.6.
The anticipated run time of an AC UPS is difficult to estimate accurately and is best found by referring to the performance graphs and tables of the manufacturer. In most cases an output efficiency Vs load current or actually run time vs load current graph is available. However, if it is not, then a general rule of thumb is that ~60% of the battery's Watthour capacity will be accessible. e.g. an AC UPS with a 5Ah 12V lead acid battery will have 0.6*5*12 ~36Watthours usable capacity Eaton provide this useful page for their products EATON UPS Runtime . Schneider/APC usually have a performance page associated with each model, here's an example APC UPS example runtime graph
When choosing an AC UPS it is important to understand what devices(loads) you are going to connect and how much power they use. Selecting a UPS with a VA figure much greater than your set up requires will mean you run the UPS inefficiently, better to get a correctly sized UPS but have additional battery packs.
Most AC UPS use IEC C14 sockets ( Incorrectly called Kettle sockets) and require an IEC C13 terminated power lead to be used. These are often seen on desktop PCs and on mains powered monitors. In a domestic or SOHO situation it is possible to use a C13 to BS1363 (3 pin socket ) multiway extension block to allow the more widely used 3 pin mains plug and 3 pin AC/DC adapters to be connected. There are a few smaller AC UPS that do use the BS1363 3pin socket, but they have integrated batteries and no option of extending duration through secondary battery packs.
Some Examples of AC UPS with 3Pin BS1363 Sockets
Some Examples of AC UPS with C14 Sockets
DC and AC UPS Pros and Cons
DC Pros
High efficiency i.e. DC to DC conversion
Simplicity of operation
Physical size compared to equivalent AC UPS
Runtime/Cost ratio is typically better than AC
Supplementary battery capacity cheaper to add
Low Voltage <48VDC intrinsically safer than AC 230V
DC UPS better suited for protection of individual devices in a distributed system
DC Cons
No universal DC Voltage standard for small devices. 5,9,12,24,48 VDC widely used.
No universal DC connector standard for small devices
Remote management and control not typically integrated in small systems
Very limited number of UK certified products for domestic SOHO use.
Typically support low power devices only and not multiple devices simultaneously.
Supply side surge protection often not included on micro DC
AC Pros
Universal 240VAC supply standard used
Simplicity of physical connection
Modular systems and expansion packs widely available
AC devices as well as AC/DC Wallwart supported simultaneously
Often include AC Surge/Spike protection built in
Maximum power ratings supported typically much higher than equivalent DC system
Remote management and control often integrated in even entry level systems.
Typically designed to support multiple devices simultaneously
AC Cons
Battery DC to AC inverters efficiency varies depending on load
When powering DC devices from an AC/DC Wallwarts effectively a second power conversion process is necessary
Physically larger than equivalent DC only system
Overall efficiency and usable capacity of a given battery is lower in an AC UPS compared to an equivalent DC UPS
Weight is higher compared to equivalent DC UPS
No AC UPS are designed for powering a single low power device, smallest system is typically minimum 4.
Standby Battery Packs - Expandable section
If you don't want to go down the dedicated UPS route and don't mind manually connecting your router to an alternative power source when a power cut occurs, then a sufficiently sized and specified Lithium-ion power bank ( Like those used to recharge a phone or tablet) or even a portable leisure "power station" (becoming popular for camping and outdoor activities) could be a viable option.
As most domestic routers use a 12Volt DC input then one approach is to simply use a portable power bank with a 12V DC output that can satisfy the maximum power requirements of the connected device. A 75Wh capacity device will cost from £120, Two established manufacturers producing powerbanks with a dedicated 12V DC output are Krisdonia and Omni. It is also possible to use a power bank with a USB C-PD port as long as its used in conjunction with a dedicated 12 V DC trigger/converter cable and importantly the PD output includes a 12v Output in its specification, many don't. The EasyLonger EL240 has both options.
The other approach is to look at the portable power stations, like those from EcoFlow, Bluetti and Anker for example. They have a greater capacity typically starting at 200Wh+ capacity and along with 12Volt DC output they often include features like a 240VAC output so you can plug in mains powered devices directly, the nominal guide price measure of £1/Wh capacity. Its worth knowing that by using a compatible DC output, e.g. 12V, rather than simply plugging into an AC output on the power station the internal batteries will last longer, that's because converting DC to AC is inherently lossy.
Some examples of Power Banks with 12VDC Output or USBC-PD-12
Some Examples of Leisure Power Stations, with multiple output voltage options
Power over Ethernet:- Backup Power options Expandable Section
Before describing how a UPS can be employed its worth briefly summarising what Power over Ethernet (POE) is, it is a technology that allows both power and data to be transmitted over a single Ethernet cable. It eliminates the need for separate power cables, simplifying installations and providing flexibility in powering network devices.
There are 3 main standards commonly used 802.3af (POE), 802.3at (POE+) and 802.3bt (4PPOe or POE++). Each standard increases the level of power that can be delivered, 15.4Watts, 30Watts and 60/90Watts, in each instance a DC voltage of ~48V is applied to the data lines of the ethernet cable.
A typical system where POE might be used is one involving multiple security cameras. The cameras are capable of extracting power directly from the ethernet cables as well as receiving and transmitting data across it. A POE network switch acts as the power source and "injects" the power on to its dedicated POE ethernet ports and in turn into the cables and onto the cameras. In such an example a UPS could be connected to the Network Switch thus protecting the operation of the cameras in a power outage. In a domestic or SOHO this standby power would most typically be provided by an AC UPS that is already protecting multiple devices in the home office. However, as POE system complexity increases the UPS is more typically going to be a rack-mountable 48V DC UPS
In smaller domestic and SOHO systems it might not be necessary or appropriate to have a dedicated POE Source network switch; in which case a dedicated POE Injector may be more suitable. This small device is connected into the relevant leg of the ethernet cables and the POE powered device is connected to just that section of the network. POE Injector devices typically require an input supply of 24-48V DC supply.
It is also possible to power non-POE devices from a POE enabled cable; a POE Splitter is a simple device that strips out the DC Power from the data lines and provides it to a dedicated DC socket/line thus allowing the non-POE device to be connected to a DC supply. POE splitters can be specified to deliver common DC voltages like 48/24/12 and 9V.
A POE Splitter could be used to provide power to a 12VDC device like a router (15Wmax) with the POE Injector connected to a UPS.
Example of POE Injector and Splitter based on TP-Link information.
Worked example system 1
Device(s) to be protected
Case 1 B4RN Router Zyxel VMG 8825 B50, Budget <£100, Required standby duration minimum 5.5Hours, Permanently wired solution.
Max rated router power = 36Watts, Typical consumption 8Watts.
UPS solution must be capable of delivering ~8 watts for 5-6 Hours = 48Watthours.
Solution 1 Mini DC LI-ion Power Solve PB600-12 PowerSolve PB600
Solution 2 Mini DC LeadAcid Cell PowerSolve PPD60 PowerSolve Datasheet
Zyxel VMG8825-B50
Worked example system 2
Device(s) to be protected
Case 2 B4RN Router Zyxel DX5301, Budget <£70, Rated power supply 12V3A, Required standby duration minimum 90minutes, Permanently wired solution
Max rated power = 36Watts, Measured Typical consumption 8Watts. Budget <£75
Solution 1 Mini DC Lithium Cell, Powersolve PS036-10A
Solution 2 Mini DC Lithium Cell, Eaton 3S Mini
Solution 3 Small AC Lead Acid Cell, APC Easy UPS BV650a (MRP£100+ but often Discounted) APC Webpage for datasheets
Zyxel VMG DX5301
Worked example system 3
Device(s) to be protected
Case 3 B4RN Router Zyxel DX5301 (36W), Vonage ATA (18W), DeCT Phone Master (12W) Netgear Switch (12W) Budget <£150, Required standby maximium for available budget, Permanently wired solution
Max rated power = 78Watts, Estimated Typical consumption 25Watts.
Solution 1 APC BE850G Lead Acid Cell, Estimated Runtime 80Minutes APC Website
Worked example system 4
Device(s) to be protected
Case 4 B4RN Router Genexis DRG7820/739/718(24W), Budget <£65, Required standby maximium for available budget, Permanently wired solution
Max rated power = 24Watts, Estimated Typical consumption 6Watts.
Solution 1 Mini DC Lithium Cell, Powersolve PUPS44 est ~6 Hours Powersolve Datasheet
Solution 2 Mini DC Lithium Cell, Powersolve PMU68W / est ~6Hours Powersolve Datasheet
Solution 3 Mini DC Lithium Cell, PowerInspired DC2 est ~5 Hours PowerInspired Datasheet
24Watt Micro DC UPS with 37-44WattHour capacity compatible with Genexis Routers