This topic

UPS solution for ONT and SH2

philip42h — Fri, 03 Jun 2022 11:23:21 GMT

I appreciate that the topic has been raised before and I am grateful to those who have already posted (including on the Digital Voice FAQs) - I know more now than when I started out! But I would like to clarify my understanding in this space so do please let me know where I have "got it wrong".

I have been on FTTP for the past five years and have recently been moved from Fibre Voice Access (FVA) (supplied via the extension wiring) to Digital Voice (supplied via DECT on the SH2 (and the 'phone socket on the back)). Previously the ONT was supported by a BT supplied Battery Backup Unit (BBU) which upon checking yesterday provided an uptime of around 3 seconds (yes, I know, I could simply change the batteries).

BT advise that in the event of a power cut the Digital Voice service will cease and that subscribers use use a mobile 'phone instead. As with many in rural locations this does not really work for us - we have little to no mobile signal and rely on Wi-Fi calling to use our mobiles at home. No power means no Wi-Fi; no Wi-Fi means no mobile communications. I can, of course, overcome this problem by jumping in the car and driving to somewhere with a strong mobile signal and recharge the 'phone along the way - so that's plan B sorted.

Plan A is to provide a UPS solution that will maintain the ONT and SH2 for the first few hours of a power-cut - I'd like 'days' but doubt that I can afford that; 'minutes' just won't do.

The BT solution appears to be provided by a pair of Cyberpower Back-up for BT Digital Voice service units - one for the ONT and one for the SH2 and, to be honest, this appears to be the best, if not cheapest solution currently available. Each is supplied with a 12V 7Ah lead acid battery. According to the specs of their respective power supply units the ONT requires up to 1.0A (at 12V) while the SH2 requires up to 1.5A (also at 12V) so this solution would be capable of maintaining the ONT for up to 7 hours and the SH2 for up to 4.5 hours. The calculation is likely to be a little more complex than "simple division" but it should, at least, give me an uptime in 'hours'.

Any solution involving a standard UPS - i.e. one providing power via 230V A/C - is likely to provide a much reduced uptime due to inversion and rectification losses along the way. On the face of it the power supplies for the ONT and SH2 appear to be 10% to 26% efficient - by simply dividing the output power by the input power. Again, the that calculation is unlikely to be quite correct but the losses at that stage will still be significant. And that doesn't yet take into account the efficiency of the UPS unit itself. So, I strongly suspect that to get a comparable uptime from a standard UPS I will need a much more capable and expensive unit. Or have I got this wrong?

Is there a better UPS solution for ONT and SH2 to give an uptime measured in hours?

Re: UPS solution for ONT and SH2

jac_95 — Fri, 03 Jun 2022 11:20:25 GMT

Hi philip42h,

Thanks for the post and welcome to the Community.

This is an automated response as I can see you have a question about BT’s Digital Voice service. Rather than waiting for a response from the Community, you may find an answer to your question by using the search bar on the Community homepage. We also have a thread that contains a wealth of info related to BT’s Digital Voice, click this link to take a look, Digital Voice FAQs.

If you have already looked for the answer to your question and have not found anything that can help, then please ignore this message. One of our Community members will be along shortly to help you further.

Re: UPS solution for ONT and SH2

yorkspark — Fri, 03 Jun 2022 19:17:08 GMT

Why do you constantly put these yellow box statements on nearly every thread? They provide little guidance and in this case is totally irrelevant to the questions asked.

Re: UPS solution for ONT and SH2

imjolly — Fri, 03 Jun 2022 19:33:36 GMT

They are automatic when there is mention of digital voice they try and cover the normal questions which are asked about DV and it was getting monotonous replying to the same questions over and over so the FAQ was was composed . I agree it does not cover some of the questions but it does provide basic information for new customers to DV

Re: UPS solution for ONT and SH2

Les-Gibson — Fri, 03 Jun 2022 20:32:15 GMT

As I'm sure you know, FVA is a legacy product, the ONT battery backup is therefore now redundant as it was only there to support telephony (as opposed to full operation of the ONT), you can therefore do as I have done; disconnect it and plug the DC jack from the mains adapter directly into the ONT.

As for the UPS, have you seen this? Cyberpower Back-up for BT Digital Voice service (FTTP) (097284)

Re: UPS solution for ONT and SH2

philip42h — Fri, 03 Jun 2022 21:16:15 GMT

@Les-Gibson

I am aware of the Cyberpower backup units - and refer to them in my original post.

As for the ONT BBU, you should be aware that it provides backup power to maintain the functionality of the ONT rather than just the now legacy FVA. It is only 'redundant if you not longer want a backup capability or have replaced it with something else ... 😉

Re: UPS solution for ONT and SH2

gg30340 — Fri, 03 Jun 2022 21:33:29 GMT

There are any number of UPS units on the market.

If you do an Internet search you will no doubt find some that will meet your needs however because you are looking for one that supplies hours of power rather than just minutes you will find that they are relatively expensive.

You obviously know the length of time that you may suffer from power outages better than I do but getting a UPS that lasts for many hours or days may be a bit excessive and it may be a better option to consider getting a "suitcase" generator. Depending on how much you are prepared to spend a generator will be able to power your ONT and hub with ease and will have additional power for other electrical devices if required.

Re: UPS solution for ONT and SH2

spile — Sat, 04 Jun 2022 07:09:57 GMT

I have the Cyberpower BR700ELCD and I use the six outlets to for my ONT, Router and NAS. I have my PC and monitors connected but of course that reduces the uptime before I have to shut down. It’s less than £100 and has proved reliable.

Re: UPS solution for ONT and SH2

philip42h — Sat, 04 Jun 2022 08:35:38 GMT

@gg30340

I have been doing my Internet research, and still am, and my head hurts! 😀

We live in rural Wales. Power (and broadband) comes via overhead cables. We regularly get power cuts when the wind brings down trees etc. and this seems to be getting worse in recent years. In last years storms folk not so far away were without power for several days - we only got cut-off for several hours towards the end of the repair cycle. Next time we might not be 'so lucky'.

I'm really not too bothered about brown-outs and short outages. The sensitive devices are on surge protected sockets and I'm not concerned about any consequent minor data loss - this isn't a mission critical / data sensitive environment here.

When a power cut has gone on beyond five minutes or so I want to ensure that the power company has registered the fact that they have an issue and be able to track its resolution. And in the 21st century that is most easily accomplished via the Internet. So, my target is to have Internet and phone line access for as long as I sensibly can under these circumstances - hence 'hours' rather than minutes though I pretty much accept that I cannot sensibly afford 'days'.

The "suitcase generator" idea certainly warrants investigation as an approach to longer outages and I've been thinking, but not quite doing, anything about it for some time as that would allow me to keep the boiler running, run some emergency lights and recharge 'phones and laptops. But that is, perhaps, a slightly different question to the one posed here ... there must be a "survivalist" forum somewhere for that! 😉

Re: UPS solution for ONT and SH2

philip42h — Sat, 04 Jun 2022 08:34:44 GMT

@spile

Thanks for that - the Cyberpower BRIC systems and APC equivalent seem useful and reliable. Having 230V A/C outlets allows users to simply plug in existing power leads / supplies and maintain a number of devices. They appear mostly aimed at enabling the graceful shutdown of the protected systems after a period of five to ten minutes avoiding equipment damage and loss of data. In this way they can fully protect against cuts of a couple of minutes or so but not that much longer.

Do you know how much uptime your system provides for you? With PC and monitors connected, and with just ONT, router and NAS?

Re: UPS solution for ONT and SH2

stevebrass — Sat, 04 Jun 2022 08:34:52 GMT

I am investigating making my own device. Batteries in series to get to 12v connected via an appropriate jack to ONT and router.

Re: UPS solution for ONT and SH2

philip42h — Sat, 04 Jun 2022 08:54:43 GMT

@stevebrass

I am similarly tempted, but don't want to "get my hands dirty" and rather hope(d) that someone would sell me a solution ...

It's easy enough to get hold of a 100Ah 12V lead acid leisure battery. On paper that would maintain the ONT and SH2 for up to 40 hours, and I really couldn't ask for more. As a backup battery solution that might work quite well - i.e. charge up before the outage event using a standard smart / trickle charger and deploy when needed.

The key benefit of this approach and, indeed, the Cyberpower 'telecoms' solutions, is that it provides the needed 12V supply without inverter and transformer losses.

Speaking of Cyberpower, they do claim to have a 36W equivalent / replacement for the BT badged solutions (DTC36U12V) that might work quite well. Although it has only a single 7Ah battery it should be able to power both the ONT and SH2 for up to 2.8 hours which might be a reasonable compromise. But I can't (yet) find anywhere that might supply one!

Re: UPS solution for ONT and SH2

stevebrass — Sat, 04 Jun 2022 09:00:25 GMT

@philip42h

Yes - I was looking at lead acid battery on a trickle charge, as well as a bunch of alkaline.

Re: UPS solution for ONT and SH2

JB2016 — Sun, 05 Jun 2022 19:04:22 GMT

@philip42h

An inverter circuit to convert voltage up from battery to 230V followed by a power supply, either switched-mode or linear, for the 12V for the Hub or ONT, will introduce additional losses that reduce the runtime available from any given battery. The more efficient solution is float-charging a battery feeding the load (the CyberPower units marketed by BT appear to do this). No doubt there are other commercial products that work on the same principle and provide a longer runtime than the CyberPower units, but they will inevitably be more expensive. I suspect you will just have to get busy with the soldering iron. If you do succeed in finding an off-the-shelf solution, then post a comment at https://bt-digital-voice.blogspot.com/

Re: UPS solution for ONT and SH2

philip42h — Tue, 07 Jun 2022 10:57:41 GMT

The key benefit of this approach and, indeed, the Cyberpower 'telecoms' solutions, is that it provides the needed 12V supply without inverter and transformer losses.
Speaking of Cyberpower, they do claim to have a 36W equivalent / replacement for the BT badged solutions (DTC36U12V) that might work quite well. Although it has only a single 7Ah battery it should be able to power both the ONT and SH2 for up to 2.8 hours which might be a reasonable compromise. But I can't (yet) find anywhere that might supply one!

I contacted Cyberpower and, somewhat to my surprise, they responded ...

The DTC36U12V is the base product we offer to BT and makes up the ONT and SmartHub2 versions. They are currently the only partner we ship this product to, so you will need to purchase the units through them.

So it would appear that BT have a monopoly on that product in the UK - that's never happened before ... 🙄

OK, I'm not sure that Cyberpower's statement is entirely correct but mostly so. The BT Cyberpower unit claim to be 24W units - DTB24U12V-BT1. Given that the ONT and SH2 are nominally 12W and 18W respectively, each DTB24U12V-BT1 would happily power either but a single DTB24U12V-BT1 wouldn't power both. The BT Shop has them flagged as "clearance".

A single DTC36U12V, at 36W would happily power both - so I confidently expect to see a BT2 unit replacing the BT1 units in the not too distant future - probably once the existing stock has been cleared. This is entirely speculation on my part ...

But I am not waiting for that - I want to have a UPS solution in place before the next power outage rather than wishing I'd been more proactive when it inevitably happens. So I've order the required pair of units - one each to support the ONT and SH2. It's only money!

Once they arrive, I'll set them up, allow the batteries to fully charge, conduct a simple experiment to get an idea of the probable uptime and post back ... 😉

Re: UPS solution for ONT and SH2

philip42h — Sat, 11 Jun 2022 19:04:49 GMT

The units arrived on Thursday. One is labelled DTB24U12v-BT1 while the other is labelled DTB24U12v-BT2. They are, identical units - the only differences being the device connector cables and the instruction leaflets: the BT1 applies to the SH2 while the BT2 applies to the ONT. They are not the 36W unit that appears on the CyberPower UK website.

They arrive with the positive lead from the battery disconnected. I assume that battery is pre-charged and that measure ensures that it stays that way in storage. Nevertheless, I plugged them in, connected the ONT and SH2 and left the system for over 24 hours to ensure that the batteries were as fully charged as they were likely to get.

Each unit has a light to show when the battery is supplying power rather than the mains. According to the leaflet, an alert sounds and this light starts to flash when the battery is down to 45% - i.e. 55% used. So first thing this morning I simulated a power-cut by simply pulling the mains plugs and waiting for the 45% alerts.

Based on the output figures for their respective power supplies I expected the SH2 to draw up to 1.5A and the ONT up to 1.0A. The CyberPower units contain 7Ah batteries so I was expecting an "on battery alert" from the SH2 side after about 2.5 hrs and from the ONT side after about 3.8 hours.

In practice I didn't get an alert from the SH2 until 3.2 hours into the test (I was actively monitoring the test at that time); the ONT alerted after about 10.7 hours (approximately since I was doing other things by then). These alerts occur at the 55% used / 45% left mark. If you believe these figures, then the CyberPower UPS will maintain:

the SH2 for around 5 hours 50 minutes
the ONT for around 19 hours 30 minutes

So that's the first few hours of the next power cut sorted as far as communications goes.

The extended runtime of the ONT is rather wasted and I suspect that I could extend the total maintenance time to around 9 hours by swapping the units over after 4h30. Either way, this gives me an uptime measured in hours which is what I wanted.

I'm sure that the actual uptime will depend on the condition of the lead acid batteries and the actual load placed on the ONT and SH2 - well SH2 largely. During the test we used the Internet as we would normally so the SH2 was providing Wi-Fi for a few devices as well as maintaining its DECT hub for 4 DV handsets.

Re: UPS solution for ONT and SH2

Mancmonkey — Tue, 28 Mar 2023 22:56:55 GMT

Thanks Philip!
An absolutely confusing mess from Cyberpower and BT, so unclear that u u need both.

Re: UPS solution for ONT and SH2

oldbuffer1 — Tue, 11 Jul 2023 09:07:22 GMT

Been reading the conversation regarding UPS for ONTs and Home Hub 2. I'm awaiting delivery of the Cyberpower UPS which presumably is being supplied to power up the ONT (or the Home Hub) since there's only one 12v output. Not much use if one device works with a power cut and the other doesn't. Looking at the specs for the ONT and the Hub I think there may be an outside chance that the single unit might power both Hub and ONT - if I make up a suitable splitter cable. Question is, is the power draw sufficient to handle both, is it bad practice to modify the supply in this way, or should I be using two separate UPS devices? I have the Eaton Mini UPS on order in case I need to use both, but I'm trying to reduce the number of devices clogging up wall space.

Re: UPS solution for ONT and SH2

philip42h — Tue, 11 Jul 2023 09:35:36 GMT

As of a year ago, you needed two devices as per my earlier post. One to power the ONT and another to power the SH2. The devices themselves are identical apart from the cables and connectors - one fits the ONT, while the other fits the SH2. At the time I purchased mine, the only source for the devices with connectors was the BT shop - I couldn't get them directly from CyberPower.

So, I use two devices with different model numbers, and, unless things have moved on, suspect that you should be doing the same.

(The BT Shop is 'down' right now so I am unable to check what is available today)

Our most recent power-cut was last week - 16-00 hours to 03-00 - and the backup solution worked perfectly (at least until I went to bed!)

Re: UPS solution for ONT and SH2

oldbuffer1 — Tue, 11 Jul 2023 10:09:31 GMT

Thanks for that. As a matter of interest is there any official ruling from BT on what accessories are available, at no cost, once full fibre is installed in your property. In particular I'm looking at Battery Backup devices and Digital Voice handsets. I had two separate online chat conversations and both persons stated that the BBU plus a couple of standard DV handsets were available f.o.c. When it came to ordering them, the third one told me I had to pay for all of them. Fortunately I retained the transcripts and was able to place the orders for phones and BBU with no charge. Would a second BBU to power either the Hub or the ONT also be available at no cost. (Battery backup to only one device would be as good as none at all).