UPS Back Up During a Power Cut

[#1]

I'm on SoGEA (FTTC), and have a 350VA UPS powering my router and DECT phones (VoIP) in the event of a power failure.

But from experience, this power backup only lasts around 60 minutes supplying the 2 pieces of equipment in the event of power failure.

So even in the scenario of being on FTTP, with backup power at the exchange, and a UPS at home supplying the ONT, Router and DECT Base Unit, you'll be completely reliant on how long your UPS battery lasts.

[#2]

@bgiles 

350VA sounds like an impressive amount of power but in reality it is irrelevant in assessing how long it will keep your router and ONT alive. Assuming that these two bits of kit consume 15W your usable battery capacity will be more like 15Ah for a 12V battery, that is, 180Wh, plus an allowance for conversion inefficiency. This is the important  factor in assessing the usefulness of a battery backed supply.

[#3]

@bgiles 

"you'll be completely reliant on how long your UPS battery lasts"

Yes, but at least that part is within your control - so you could increase the capacity of the UPS battery etc.

Unfortunately, like the rest of us on FTTC, you are still reliant on the back-up capabilities in the cabinet - which obviously are outside your control.

[#4]

@Baldrick1 

Assuming for a moment that "VA" as the same as Watts - I know that it isn't, but let's ignore Power Factor for now - then that capacity at a drain of 15 Watts, should be able to be powered for almost 24 hours, shouldn't it?

@bgiles 's UPS must be incredibly inefficient, (or faulty?), if it is only managing one hour?

[#5]

@Mr_Paul The sole purpose of the UPS is to guarantee power during router firmware upgrades.

It also prevents it rebooting abnormally as a result of a brief power cut, which we all experience.

As the DECT base unit is adjacent, that's also plugged in to the UPS.

I just wanted to point out that I wouldn't want to rely on a small domestic UPS to maintain what is a critical service to some, i.e. those who have poor mobile coverage, or care lines etc.,

Unfortunately those people already on FTTP or SoGEA, currently have no other option available.

[#6]

So even in the scenario of beingnot sure Openreach have on FTTP, with backup power at the exchange, and a UPS at home supplying the ONT, Router and DECT Base Unit, you'll be completely reliant on how long your UPS battery lasts.

and TBH we're making assumptions about FTTP backup power. Yes, we know there is no powered equipment between the customers ONT and the headend in the exchange, but we're making assumptions that there is some reasonable backup in the exchange, mainly because it should be relatively straightforward!. However I'm not sure that OR will tell us what backup is actually available?. Lets face it, they weren't very forthcoming about the lack of backup for FTTC cabinets...

[#7]

@MisterW 

"but we're making assumptions that there is some reasonable backup in the exchange"

From my experience of working in telephone exchanges, albeit 40 years ago, the exchange batteries and generator were sufficient, (assuming that the fuel tank was full, as it usually was), to keep the old Strowger equipment etc going for many days - even weeks!

[#8]

@Mr_Paul

yes, but that's probably all getting a bit long in the tooth now and getting rid of it is all part of the PSTN shutdown.

They'll need new kit for backup of the FTTP network and they (Openreach) may have taken a no need for long term backup approach on the 'no call for it gov' basis!

[#9]

@MisterW 

"but that's probably all getting a bit long in the tooth now"

Maybe, but diesel engines last a very long time, if they are well maintained - and the ones that I remember were very well maintained!

"and getting rid of it is all part of the PSTN shutdown."

Do you know this to be fact, or just your opinion? I know that part of the plan is to close many of the exchange buildings, but my understanding is that the remaining Core Access points would all be in existing exchange/repeater station buildings?

"They'll need new kit for backup of the FTTP network!"

Are you talking about new transmission equipment, or power equipment?

[#10]

Do you know this to be fact, or just your opinion? 

No, I don't know this for a fact but I'd guess that any existing backup is old technology and takes up a significant amount of space and is expensive to maintain.

[#11]

"No, I don't know this for a fact but I'd guess that any existing backup is old technology and takes up a significant amount of space and is expensive to maintain."

Well, yes, diesel engine generators and lead-acid batteries, (as I remember), are an old technology. But that doesn't mean that there is anything wrong with them and they need replacing or scrapping en-masse.

The generators and batteries were often below ground, along with the cable chamber, underneath the main exchange building - so I don't see why "space" should be an issue?

How "expensive" something is can be a matter of opinion. I suppose it depends on how much say the "bean counters" have in the decision. After all, anything that costs even a small amount of money, but doesn't in itself bring in any revenue, could be said to be expensive.

[#12]

I suppose it depends on how much say the "bean counters" have in the decision.

In my experience the 'bean counters' make the decisions, technical experts have very little say!

Its the "we've made our decision, now don't confuse us with facts" scenario

[#13]

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@Mr_Paul wrote:

@Baldrick1 

Assuming for a moment that "VA" as the same as Watts - I know that it isn't, but let's ignore Power Factor for now - then that capacity at a drain of 15 Watts, should be able to be powered for almost 24 hours, shouldn't it?

@bgiles 's UPS must be incredibly inefficient, (or faulty?), if it is only managing one hour

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You can’t ignore power factor. There can be a lot of specmanship at play. What you can derive for certain is that the UPS can deliver about 1.5A  of current at 240V, there’s no mention of how many Wh can be delivered by the battery.
This gets even more complicated when the load is a switched mode device pulling chunks of current. This is reflected as a very low PF It’s in a different league to say an induction motor. If you look at the rating plate on a small PSU you might read something like: Input 240V a.c 1A, I.e. 240VA. Output 12V 1A dc, I.e. 12W. If you treat VA as being the same as watts it ain’t half going to get hot!

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[#14]

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@bgiles wrote:

I'm on SoGEA (FTTC), and have a 350VA UPS powering my router and DECT phones (VoIP) in the event of a power failure.

If your UPS is like mine (an APC unit with the same rating) then you may find as I did that you can fairly cheaply double its run time.  I looked inside mine and found it has a small 4.5Ah battery, fitted in a space made for a very much larger battery.  I spent some time looking around and found a 9Ah battery that was a slot in fit, didn't need to adapt anything, I just unplugged the old battery wires and plugged them to the new battery and put the case back together.  I did this a while ago and it's fine, it actually runs for slightly longer than double the run time of the old battery on the same load.

These things aren't at all efficient, though, they have a lot of losses internally, so although it originally had a 12V 4.5Ah battery, suggesting it had a capacity of 54Wh, the usable capacity was about 2/3rds of this.  With the new battery I think the usable capacity is now a bit more than 2/3rds of the 108Wh capacity, so a worthwhile upgrade.  The new 9Ah battery cost £21.66, so not too expensive.

[#15]

@JSHarris I have several APC Back-UPS350 in the house, serving various pieces of equipment, like CCTV.

I replaced the battery in 2022 with a CSB 12V 7.2Ah, after it failed the a routine battery test.

I did a run test the year before with just the DrayTek router and DECT, and it ran for about 60 minutes. However, as the battery may have been past its best, it probably didn't give an accurate result.

@Baldrick1 I can run a test using a spare APC Back-UPS350, which has a new 12V 7Ah battery, and will be fully charged beforehand, connect a Billion Router, and BT DECT Base, check the draw wattage and current using a plug in monitor, and see how long they run for.

The router will of course NOT be connected to internet, so consumption will probably be less than when connected.

Would this be useful in establishing a realistic estimate of run time in the event of a power failure?