UPS Configuration

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My web site runs on a Pi and I want it and my laptop to run for as
long as possible during a power failure. I'm looking for a UPS for
about $US100.00. An orderly shutdown of the Pi would be good but
extending the backup period is much more important. My laptop doesn't
need extra battery backup but the Pi and a router do. All interaction
with the Pi is via Microsoft remote desktop. It seems that UPS
software is a significant enhancement to the hardware and I would
prefer to run it on the Pi because my computer is not always on-site.  

Any suggestions would be very welcome and a recommendation of specific
software or a particular UPS would be a bonus.

Re: UPS Configuration
On 31/03/16 13:27, Gordon Levi wrote:
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Mmm. You have to run a router as well?


TBH if the router takes '12VDC' from a wall wart, or whatever, Id  
suggest the simple expedient of a car battery plus flaot charger, plus a  
switching regulator  
http://www.dimensionengineering.com/products/de-sw050 to drop the 12v  
down to 5V and power the pi from that.

Permanently.

You probably have several days of life in the average car leisure battery.



--  
The theory of Communism may be summed up in one sentence: Abolish all  
private property.

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Re: UPS Configuration
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And a suitable charger can easily be built round a Unitrode UC3906

--  
Stuart Winsor

Tools With A Mission
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Re: UPS Configuration
On Tue, 05 Apr 2016 22:07:30 +0100

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It's a very nice chip and even includes temperature compensation but there is
one potentially dangerous condition that can arise (and I've actually seen it).

If the external drive transistor goes into thermal runaway the battery will get
the full uncontrolled supply voltage. This happened in a commercially produced
unit. The retaining bolt had worked loose from the transistor and a 6V battery
was being charged. The incoming supply was a simple transformer/rectifier/cap
that was pumping out about 14V. With no effective heatsink the transistor went
S/C and the battery got *very* hot and swollen. Fortunately this was spotted
before it exploded.

Because of the way this transistor is driven in the reference design, there is
no way to turn it off once internal leakage becomes significant. A more
conventional emitter-follower arrangement would be more stable, and the
transistor would have to get much hotter before leakage became severe enough to
'self-bias'.

--  
W J G

Re: UPS Configuration
On 31/03/2016 15:32, The Natural Philosopher wrote:
<SNIP>
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Choose a cheap UPS which uses a 12v battery (e.g. APC ES550 which uses a
single 12v 7Ah) - tap the battery directly to feed an efficient +5v
regulator (via a 3A fuse), then initially feed the router wall wart from
the mains output.

For an encore, you can then look at feeding the router from the battery.

Note that the battery voltage when on charge could be high as 14v.

If you choose a UPS with any kind of management interface you can plug
this into the Pi and then use Network UPS tools to manage a shutdown.

This method means that the hardware task is reduced to sourcing a DC-DC
converter, rather than sussing out how to float charge a battery







Re: UPS Configuration
On Thu, 31 Mar 2016 23:27:07 +1100, Gordon Levi wrote:

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For just powering the RPi, I'd look at either the Pi Supply UPS PIco or  
the Pimoroni MoPi


time and can also use larger LiPos. They offer a 3000 mAh pack which  
claims 8 hours runtime with the mains off.


battery in the 6v - 20v range, so using a 12v lead-acid battery (or a few  
in parallel) should cover more or less any amount of power outage you're  
prepared to pay for.

However, running a router is a somewhat different story. To power that  
plus your RPi you'll most likely need a UPS with mains level output to  
run the wall-warts for the RPi and router because they may want different  
input voltages. My commodity D-Link router wants 12v, so can't share a  
wall wart with the RPi.

While you can pick up mains UPS for under $100 they're really only  
designed to let you shut down a PC or EPOS system and may assume you'll  
be around to do a manual shutdown when you see the lights go off. That  
said, a 400 VA UPS might run your RPi and router for around 8 hours if  
the UPS and the RPI and router wall warts are 100% efficient. If we say  
that the UPS AC converter is 90% efficient and the wall warts can manage  
80%, make that something under 6 hours runtime as an off-the-head  
guess.    

======
If you want to go much beyond that in UPS capability, the costs go up. I  
didn't see anything on the low cost range that could tell my computer  
about power outages. We go through periods where the mains 'flick': the  
power drops for a few mS, enough to cause a PC's electronic mains switch  
to turn off and I decided that a UPS would be a good way to stop that  
happening and that it would be a good idea if it could let the computer  
know when the mains was off.  

So, I did a fair bit of research before buying a UPS and ended up getting  
a Riello Sentinel Pro 700, which gives an off-mains runtime for my house  
server (Dual Athlon @3.2 GHz) of 55 mins and provides a serial link for  
notifying the server of prolonged power outages etc so it can shut down  
cleanly.  

I could also run my router off it (4 mains outlets) but decided not to  
since there's no easy method of powering off the router at the same time  
as the server and leaving it sucking on a fully drained battery is a good  
way of wrecking it.

HTH


--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
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Re: UPS Configuration
On Thu, 31 Mar 2016 14:44:21 -0000 (UTC), Martin Gregorie wrote:

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Some do have USB ports for connection to a host PC but not all.

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Surely the UPS shuts itself down when the battery gets towards flat?
After signalling "low batt" to the host equipment a minute or two
earlier. Mine does.

As for makes, I'd be a bit wary of APC units. They have a habit of
cooking the batteries. The charge rate is set for quick recovery and
restart after an outage but doesn't switch to a trickle/float level
when the batteries are fully charged. Don't know if the buget models
are any better mind.

--  
Cheers
Dave.




Re: UPS Configuration
On Thu, 31 Mar 2016 16:21:00 +0000 (GMT)

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    I have seen this, the flatteries on mine were so cooked there was
no way they were ever coming out again the plastic was bulged round the
metal of the case. Lbooyd hot it were TAAAW.

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    WHAATTT!! REAALLLY! Oh ye gods that's insane.

--  
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:>WIN                                      | A better way to focus the sun
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Re: UPS Configuration
On Thu, 31 Mar 2016 19:25:19 +0100, Ahem A Rivet's Shot wrote:

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and

Seen that in a rack mount unit. Would have required serious metal
surgery to get them out. Last example was my Smart UPS 700, they
almost caught fire:

https://www.flickr.com/photos/allsorts-60/16591022171/

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But it sells battery packs, that and the routine testing unless you
turn that feature off.

I've "got at" my APC UPS and it now charges at a float rate much
closer to what Yusa say is the float rate for 12 V 7 AHr batteries.
Takes much longer to reach the 15% charge level before it'll restart
but WTH the unit now sits at just over 30 C and doesn't feel warm
instead of over 40 C and decidedly warm. I've also added a speed
controlled fan in the slot that would have taken an SNMP card.

--  
Cheers
Dave.




Re: UPS Configuration
On Thu, 31 Mar 2016 16:21:00 +0000, Dave Liquorice wrote:

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Good point, and one that I missed.  

FWIW I'm running my Riello in 'online' mode, i.e. the battery is  
continuously in circuit and being charged at the same rate as the  
external load is pulling power from it. All surfaces are cool to the  
touch and its reporting an internal temp of 30C.  

So, going upmarket a bit at least got me decent battery management.  
IIRC it uses a pair of 2.7 Ah 12v SLAs.


--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
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Re: UPS Configuration
On Thu, 31 Mar 2016 21:14:17 -0000 (UTC), Martin Gregorie wrote:

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Must be quite a low output to manage the normal "10 mins, full chat"
specification of most small UPS's. IIRC the 2 x 12 V, 7 AHr,
batteries in my UPS can only manage 10 mins or so at the full 700 VA.
If I'm quick to shut down my (greedy) PC and monitor it'll keep the
essential modem (itegral switch) and VOIP/DECT phones up for the best
part of 6 hours. The server auto shutdowns 2 mins after the power
goes out.

--  
Cheers
Dave.




Re: UPS Configuration
On Sun, 03 Apr 2016 20:06:37 +0100, Dave Liquorice wrote:

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The UPS thinks it can sustain the load it sees (i.e. my house server),  
which averages around 30w (125 mA at 240v), for 55 mins. The continuous  
load factor is 9% of the UPS capacity.

Yes, its not huge - 700 VA isn't a lot of capacity. As I think I said,  
what I bought was its ability to tell the computer it supports when power  
goes off and comes back on rather than sheer capacity. What it was always  
intended to do was to tell the computer when power is lost or restored so  
the UPS monitoring process on the computer can say "OK, power was lost x  
minutes ago and hasn't come back, so shutdown NOW" to the kernel.
    

--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
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Re: UPS Configuration
On 03/04/2016 20:06, Dave Liquorice wrote:
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That 7AHr capacity is at the 20 hr rate. i.e. The current can you draw  
for 20hrs before the cell is discharged.

That gives 20 x 0.35A = 7AHr (20hr).

If you draw more current the AHr rate is lower. I'd expect the same  
cells to be nearer 5Ahr if you draw a large current.

If they are in parallel you have 12V and (5 + 5)AHr = 12v at 10Ahr =  
120WHrs. If the UPS is rated at 700VA then you'll get

120/700 = 0.17Hrs = 10.2 minutes. +/- depending on load, temperature,  
battery age, phase of the moon etc.



Re: UPS Configuration
On Mon, 04 Apr 2016 21:40:51 +0100, mm0fmf wrote:

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Aye.
  
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Series, but it makes no difference, the amount of stored energy is
the same. But of course the current required at 24 V for 700 VA is
half that at 12 V, a mere 30 A against 60 for 12 V...
  
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Which is about what it can do.

--  
Cheers
Dave.




Re: UPS Configuration
On 31/03/2016 15:44, Martin Gregorie wrote:
[UPS]
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Fit a relay on the 12V line to the router coming off a GPIO line on the Pi.

---druck


Re: UPS Configuration
On Thu, 31 Mar 2016 21:00:52 +0100, druck wrote:

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That assumes my RPi is on the UPS. It isn't at present and, even if it  
was, its most unlikely that I'd ever need to run it 24x7.


--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
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Re: UPS Configuration
On 31/03/2016 22:00, Martin Gregorie wrote:
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Well if you are going to leave any system running 24x7, the RPi will  
cost almost nothing to do so, so why not?

---druck


Re: UPS Configuration
On Fri, 01 Apr 2016 06:22:18 +0100, druck wrote:

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If it was doing a 24x7 job it would probably be on some sort of UPS, but  
as it is doing almost nothing apart from being kept up to date and backed  
up, so keeping it powered would just waste power.  

My main development activity is currently on the UPS supported house  
server and, as it is mainly Java programming and web page maintenance, is  
not suitable for transfer elsewhere.


--  
martin@   | Martin Gregorie
gregorie. | Essex, UK
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Re: UPS Configuration
On Thu, 31 Mar 2016 23:27:07 +1100, Gordon Levi wrote:

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NUT - Network UPS Tools http://networkupstools.org appears to be
available for Raspbian. Supports most if not all UPS's out there.
It's a client/server model. Server on the Pi with the UPS connected
to the Pi (probably by USB these days). Server monitors the UPS and
can shutdown the Pi on battery low.  Client on laptop networked to Pi
could shut the laptop down when the power goes or a minute or two
after.

--  
Cheers
Dave.




Re: UPS Configuration
On 31/03/2016 13:27, Gordon Levi wrote:
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$100 would buy a lot of internet hosting for your web site. Maintaining  
power during failures is no longer your problem.

I used to run various internet services from a low power Linux machine  
at home. The more users I had the more I'd worry about power fails. I  
was working away from home more and that meant having to explain to my  
wife and family about restarting stuff if the mains failed.

Then one day I got a cheap VPS and moved everything from home to the VPS  
and haven't looked back. Running servers from home is, IMHO, a mugs  
game. Stick them in a data centre and pay a few pence a day for someone  
else to worry.

YMMV.

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