Battery Power for TG585

[#1]

We had a power cut yesterday just as I sat down to check my e-mails at the iMac. I only have a PAYG dumb phone and my iPad is WiFi only, so we were cut off from the internet. It occurred to me that, since the router works from an external power brick, it should be easy to make up a suitable battery pack and lead to power the router so that the iPad would be fully functional during power cuts.
Before I set about re-inventing the wheel, has anybody already done this?
Trevor

[#2]

Will you remember to keep a charged battery available 
Alternatively, a low cost UPS  would run your iMac as well for a short period (if they are near each other  ).

[#3]

I fly electric RC planes so yes, I always have loads of charged batteries around - just waiting for that rare weather window when it isn't raining or blowing a gale!
I was just wondering what sort of battery box people might have come up with, or even if there is anything available commercially?

[#4]

May be worth getting a TG582n for this project. You'll need less battery cells, it's only 12 volt, IIRC the TG585 is 22 volt.

[#5]

I just looked at The TG582n PSU & can confirm it is 12v with polarity + Inner & - Outer

0.35A Max
Output 12v 1.0A
Therefore possibly a motorcycle / Alarm system battery may be ok to use
Not sure about the RC plane batteries as not enough knowledge in their voltage etc
The TG585 v7
0.5A
22v 545mA
See image for polarity

[#6]

Not sure if the Technicolor is expecting a regulated supply or would be happy with a 11.5 - 14v source which you'll get from a sealed lead acid battery.
You could always bung a couple of 1N4001 diodes in series with it to drop it by 1.4 volts.
In fact a schottky diode in line with the existing PN PSU and a few  diodes in series with a SLA battery could make a reasonable effective UPS. As long as your mains supply > SLA voltage plus the diodes you should be ok.

[#7]

Thanks guys. I do have 5 cell LiPo batteries, nominal voltage 5 x 3.7v = 18.5v, fresh off charge voltage more like 5 x 4.15v = 20.75v I wonder whether this would be enough? If so, all I need to do is check on the power plug size and make up a suitable lead - or splice one of my usual battery connectors into the lead from the existing brick!

[#8]

I suspect this could be trickier than it looks.  The modem is drawing around 10 Watts of  power from the figures given, so the capacity of the batteries would need to be adequate for a sustained discharge.  The router you mention has a switch mode supply IIRC and output voltages are usually quite accurate, generally within 0.25 volt, so I wouldn't risk trying it with anything too far away from nominal.  I was considering this job myself fairly recently and concluded that 2 x 12V 10Ah sealed lead acid batteries would probably work quite well.  I believe that the answer is to "float charge" the batteries at about 26.5 Volts and regulate the output down to the required 22.5V.  These figures provide about 4Volts of headroom on the regulator.  This would allow the use of linear regulators rather than switching types, with their attendant noise issues.  The dissipation at the regulator is therefore:  4Volts x 0.5 Amps = 2 Watts.  A small heatsink would suffice to maintain the regulator temperature within tolerable limits.  Keeping the batteries charged presents similar issues and is somewhat more complex.  The supply has to drive the router as well as trickle charge the batteries in normal operation, so would need to be about 25 Watts.  A 25 VA transformer would probably be adequate, but regulation figures for transformers are somewhat flexible and you'd be likely to end up with about 45 Volts if you use a dual 15Volt type in series.  The dissipation for this input regulator would then be (45-26.5) Volts x (modem current 0.5A + trickle charge current 0.2A )Amps.  This gives 13 Watts dissipation.  It'll get hot!!  If you add all the numbers together, Modem power (10 Watts) + input regulator dissipation (13 Watts) + output regulator dissipation (2 Watts) plus a small margin for other losses, it all comes to a tad over 25 Watts.  Not impossible, but tricky and power hungry as well as costing a fair amount to implement.

[#9]

Are you suggesting that the power brick contains a switched mode PSU? Somehow I  would have expected it to supply a fairly rough and ready DC feed and the real regulation and conditioning to be inside the router itself. Is there an easy way to find out?
On the power consumption question, my LiPo batteries are around 3Ah capacity and 10w at 22v equates to less than half an amp so I could expect 5 to 6 hrs from a five cell pack. I would normally have at least two packs fully charged at any given time so that would probably keep me going long enough to begin to worry about re- charging the iPad!
I must admit that nobody has come forward having already done this so maybe, as you say, there is more to it than just plugging a battery into the back of the router.
Trevor

[#10]

Found this link you may find interesting.
http://homemadecircuitsandschematics.blogspot.co.uk/2013/03/simple-dc-ups-circuit-for-modemrouter.ht...
As I said before, things may be easier with a 12v router. 

[#11]

I use a cheap UPS I got from Scan (this looks like the current version of it) for my modem, PC based router and RouterBoard primary switch (which can also be a router).
We had  a 30 minute outage earlier tonight, I powered down the PC router and used the RouterBoard + NetGear modem and that UPS was enough to keep me on line for the duration.
If I'd have left the PC Router on I'd probably have only got 5 minutes...

[#12]

Possibly depends on the type of 585 router.  My TG585v7 is definitely a switch mode supply job.  Output voltage 22.7 Volts.  Looking at a popular online auction site, the ST585v6 appears to have the more normal power brick type supply.  I'm guessing that newer modem/routers will almost all have switch mode supplies.  Probably cheaper to supply in bulk.  The older linear transformer units contain a fair amount of metal, so more costly to make and have higher shipping costs due to greater weight, plus SMPSUs will operate across a range of input voltages and that means not needing different units for different markets.  Sure, the external plug casing and pins may be different, but the giblets are the same.  If you're working in millions, all this stuff matters.  If you select a modem with a linear supply, it should be more tolerant of higher input voltages.  I own an old Linksys WAG54GS which has a 12 Volt supply and the off-load voltage there is around 18 Volts.  Looks like your best option is a modem designed to operate from a 12 Volt linear supply which should be tolerant of the higher input voltage from a float charged lead acid battery.  I'm not sure what effect supplying under voltage would have.  The internal digital electronics will almost certainly be using 3.3 or 5 Volt supplies, but maybe the ADSL output stage needs something higher.  I've never bothered to find out.  You'll also need to check on the discharge profile of LiPo batteries.  I suspect they may hold for a reasonable time and then the voltage will plummet suddenly.  Generally, 3AH doesn't mean you can obtain 3 Amps for 1 hour, or even 1 Amp for 3 hours.  Usually, capacity figures are quoted at a 10 or 20 hour rate.

[#13]

Thanks again for the info and links - very interesting. If we were subject to frequent power interruptions I would definitely be looking at the UPS solutions. However this weeks was the first for many years and I fear that any dedicated backup battery would die of old age before it was ever called upon, hence the idea of working something out that uses the regularly recharged and renewed stock of model flying batteries.
To be honest, the interruption isn't a big issue, it's just that it would be nice to be able to get on the internet during the power cut, for example to check whether our problem was already known to the electricity supplier.
Our router is a v7 so it sounds like it does have a switch mode PSU. I'll try to get around to checking the off load voltage of the supply brick some time (and seeing how heavy it is!) just to make sure. We do have an old Speedtouch router which might be a better bet. It's not wireless though so not much use for the iPad but could at least be used with a laptop - always assuming of course that it will work with ADSL2+. . . .
The real question of course is will I ever get around to doing any of this? And if I do, will I have succumbed to the lure of fibre before we get another power cut anyway!

[#14]

Maybe this would be a good suggestion to router manufacturers.
With so many things run on batteries these days, mobile phones, tablets, laptops etc, it seems a big oversight that the main piece of equipment for connecting to the internet is mains powered only.
UPS is one solution but with the router in one room, multiple pc's, smart tv's in other rooms it would be expensive to power all, but battery backup would be a great idea.

[#15]

Quote from: avatastic

I use a cheap UPS I got from Scan (this looks like the current version of it) for my modem

You can get an APC Back-UPS ES 400 for £54 including VAT and free delivery from eBuyer.
Edit: Liebert PSP 500MT UPS 500VA 300W 230V USB 4 Output Connectors £49.98inc. vat (free delivery)