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[roseway]

How can you "try" it? What happened to me wasn't planned, I didn't plan the power cut.

You recommended that anyone using a UPS should manually force a restart during a mains power cut.

http://forum.kitz.co.uk/index.php/topic,18069.msg327732.html#msg327732

[William Grimsley]

Yes, I did. But, you can't try this out unless you get a power cut that affects most if not all of the cabinets' area.

[NewtronStar]

SLA battery to provide 12V DC to the device and employing a sufficiently capable PSU to keep the SLA battery trickle-charged.

Yes I used a Car jump starter pack which also has a 12v DC cigarette style socket which supplied the HG612 with power for 3 days it could have gone on longer but my testing was complete and used the PSU to keep the starter pack topped up.

Cheap and cheerful ups for only one device 

[PhilipD]

Hi

I have always considered the conversion of 240V AC to 12V DC (incoming mains supply to the UPS battery), then 12V DC to 240V AC (UPS battery to a "protected" AC output), then 240V AC to 12V DC (typical switching mode PSU for a typical modem/router) to be both inefficient and convoluted! 

If I should ever have a need for an interruptible power supply for a modem/router I would probably consider using a SLA battery to provide 12V DC to the device and employing a sufficiently capable PSU to keep the SLA battery trickle-charged. When the mains input is absent, the SLA battery supplies the load. Essentially the SLA battery is floated across the PSU output (and due to the low impedance of such a battery it would also provide smoothing of the PSU output).

This is a really good idea, however we would need to supply around 13.8 volts to keep the battery float charged at typical room temperatures, and if the modem/router is powered directly from the battery whilst being charged it will be receiving too much voltage although may be okay.  Another problem though is a lead acid battery charger usually has at least two modes of charging, bulk and a trickle charge at 13.8 volt, so using an off the self charger and powering the modem/router directly from the charging battery will draw enough current for the charger to stick in bulk charging at a much higher voltage, damaging the battery and the modem/router.  You could buy just a dumb trickle charger that only outputs 13.8 volt, but chances are it will be rated at too low a current to drive a modem/router.  So it isn't a good idea to run the modem/router direct from the battery whilst charging.

Some routers/modems need 15 volts so a 12 volt battery may not work at all.

In addition to the charging issues above, during a prolonged power outage we need to disconnect the battery at around 10 volts to prevent damaging it, however the modem/router might have stopped working before then anyway as the voltage is too low.  When power comes back on with a flat battery, the current drawn may keep the voltage too low to power back up the router/modem, and a worse case is the modem continually syncs then crashes due to a low voltage, syncs again and crashes, which of course will make the DLM a bit excited!

So to do this properly then at least two power supplies are required, perhaps a boost DC-DC convertor to keep the battery voltage at 12 volts minimum when online and running the modem, then some monitoring circuitry to switch off the battery at 10 volt to prevent damage, plus the charging circuitry to bulk then float charge. 

You can probably find something from Ebay that will do all the above, I've seen DIY solder kits before, or it could be built using a micro-controller and relays.  Of course with a full blown UPS you can also run other things during a power cut.

Here we are, something like this: http://www.batteryspace.com/12VDC-Micro-UPS-battery-backup-board-for-12.8V-LiFePO4-/-12V-SLA-battery.aspx

Regards

Phil

[Weaver]

@PhilipD I defer to your clearly greater expertise. :-) Seriously.

Re: Snake oil. I don't know what the quality of the output of these commercial small UPS's is like, I haven't measured it, hence the "if" in my earlier post. So if the output happens to be clean anyway, then obviously there's no issue.

A second point is that the signal voltage I get is really really low, <= ~ -65dB d/s attn., so any noise, if present, would be a big deal, whereas for normal users with shorter lines, the same noise input would not be significant. So aside from your good points about the filtering capabilities in modems' cheap PSUs, I should have qualified my earlier post with a comment concerning long lines.

So lots of caveats need to be appended to my earlier, hasty, post.

It may be that the improvements I saw when fitting filtering devices were a red herring, non-reproducible, and were just down to the vagaries of what sometimes happens to your sync rate when you power down and up again. For reasons poorly understood, I do occasionally seem to get an improvement in downstream sync rate just by forcing a resync when a link has been up for many days.

The link to that controller for an SLA battery is very interesting, seeing as I don't get a run time that is anywhere near long enough from my current inexpensive UPSs. Many thanks for that.

[sevenlayermuddle]

Inspired by this thread I did a few searches for devices with battery backup, found this...

http://www.powerinspired.com/ipower-12vdc-ups-2100ma-p-1904.html

Or for Home Hubs...

http://www.powerinspired.com/ipower-12vdc-ups-2100ma-bt-home-hub-p-1905.html

It's quite an elegant solution, if a few tens of minutes back up is sufficient?

Note I would always exercise caution in selecting manufacturers and quality for any such 'always-on' devices, on the basis of fire-safety.   I have no reason to think that one is n any way unsafe but as I'm not familiar with it, I'd want to do more research on its pedigree first.

[Weaver]

I saw that powerinspired.com device. It's a shame it only gives you ten minutes or so of runtime. But that's all they can reasonably do in such a physically small, convenient package. I would need four of them (three modems and a WAP) plus another UPS for LAN switch and router, and I would need at least five hours runtime, on the basis of the infrequent power outages overnight during the last decade or two. I'm afraid ten minutes won't really do. The idea is to not have to ever get up in the night to fire up the 2kW Honda generator.

[sevenlayermuddle]

Looking at the runtime table in the spec sheet, and without researching old threads to remind myself of Weaver's hardware, I think most domestic routers would probably survive more like 30-60 minutes. 

http://www.powerinspired.com/brochures/BR-UPS-IP.pdf

But I completely agree, it is a non-starter as solution for longer duration power cuts, as are undoubtably common in places.

[Weaver]

I have three Dlink DSL-320B-Z1 modems and a Zyxel WAP that all need UPS support so the number of these mains plug-type 12 V devices that would be required means that it's starting to get expensive. And that doesn't cover my router, A Firebrick FB2700 plus an HP LAN switch which take 230 V AC mains straight in, not the cylindrical 12 V barrel plugs this device caters for. So basically I've got too much kit and kit that doesn't fit the scenario.

[sevenlayermuddle]

I wasn't trying to twist your arm Weaver, I know these devices are not appropriate to you.

I'm actually becoming a little but more tempted myself... One for the modem and one for the router would at least keep WiFi up and running for a while when the power goes off.   My ethernet switch takes 240V, but keeping  WiFi without wired LAN would be an acceptable compromise.

I probably won't though as I do worry (maybe too much) about the safety issues, these devices contain Li-Ion batteries which have a dubious fire-safety reputation.   Or at least as I understand, they are somewhat dependent on the charging electronics being 'just right', the price for design-faults being  fire.  As stated, I have no reason to doubt these specific devices' safety but still I'd worry, being connected 24/7.

[roseway]

these devices contain Li-Ion batteries which have a dubious fire-safety reputation.

Lithium-ion batteries are used all over the place these days, including heavy duty uses in professional power tools, for example. I haven't done any research, but I'd guess that what you say is probably a relic of the early days with this technology, before charging requirements were properly understood.

[PhilipD]

Lithium-ion batteries are used all over the place these days, including heavy duty uses in professional power tools, for example. I haven't done any research, but I'd guess that what you say is probably a relic of the early days with this technology, before charging requirements were properly understood.

Those charging requirements though eluded hover board manufacturers http://www.bbc.co.uk/news/technology-36727652 and not long before that another famous recall was the EE power bar http://ee.co.uk/power-bar-recall

I think caution is needed with anything left on 24/7 and unattended where lithium batteries are concerned, and especially if the manufacturer is largely unknown, as these things are often made cheap and cheerful in China with fake safety marks and can lack any sort of safety features or rigorous testing.

I UPS from someone like APC is probably the safest and most flexible solution.

Regards

Phil

[sevenlayermuddle]

Lithium-ion batteries are used all over the place these days, including heavy duty uses in professional power tools, for example. I haven't done any research, but I'd guess that what you say is probably a relic of the early days with this technology, before charging requirements were properly understood.

Several useful links already provided by Philip, and let's not forget the aircraft fires that grounded the 787 fleet...

https://en.m.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems

A good article in the Economist outlines the problem...

From http://www.economist.com/blogs/economist-explains/2014/01/economist-explains-19

Catching fire if something goes wrong, then, is in their nature.

I would agree that the fire risk from Li-Ion, at an individual level is really quite low.   For that reason I'm happy to use a mobile phone or tablet - the benefits of convenience far outweigh the risk.

I also tend to trust that the big names in consumer electronics, Samsung Apple etc have done their homework, and employed trustworthy designers and manufacturers, further reducing the risk.  And even if something goes wrong, the big-names are likely to recall, as with the EE & Hoverboard Li-Ion recalls linked by Philip, and as Sony did over Li-Ion laptop batteries a few years ago. 

I'm less inclined to trust Li-Ion device a manufacturer I've not heard of, also less inclined to trust a Li-Ion device that is always connected.   

[currytop]

There are several lithium battery technologies, some more fire prone when abused than others. Lithium polymer in soft cases can burn fiercely if severely provoked. Lithium-ion is a term often used vaguely by marketeers and may mean various chemistries. Lithium iron phosphate which is that typically used in power tools is generally considered extremely robust and safe, but with a lower terminal voltage.

Any battery charged erroneously can overheat as can the charger. For example the old nickel cadmium batteries which we've used for decades can rupture explosively if dramatically overcharged. Properly designed systems especially using LiFePO4 chemistries are really very safe.

[Weaver]

@Sevenlayermuddle - :-) No, I wasn't being arm-twisted. I myself just rather fancied these plug-type devices initially, until I read about the unimpressive run-time.