UPS recommendations?

Hi,
I've used one of those plug-through energy monitors to measure the Pi
and some other equipment that I'd like to protect with a UPS.
networking stuff:
26 W (average over 6 hours)
27 W (instantaneous reading when I checked)
49 VA (" ")
PF 0.54 (" ")
Pi + external hard drive
6 W (average over 14 hours, including some intensive file transfers)
5 W (instantaneous reading when I checked)
13 VA (" ")
PF 0.41 (" ")
So I figure 65 VA + safety margin. I'd prefer a small, quiet UPS (to
go in a cupboard) with surge protection.
It would be a bonus if it can be configured not to shut the Pi down
immediately when the power goes out (in case of brief interruptions) &
to wait a few minutes after the power comes back on before turning the
Pi back on (in case the power flickers before staying on).
I'd be grateful for any recommendations.
Thanks.
Reply to
Adam Funk
Loading thread data ...
APC Back-UPS 500 (500VA)
It has serial and USB interfaces and I think it is compatible with upsd.
The Back-UPS 300 is a little smaller/cheaper but only has the serial output.
I have a few of the 300's.
Most small UPSs have IEC (kettle) sockets, so you might need to make up a standard 4-way 13A extension with an IEC plug on it...
Gordon
Reply to
Gordon Henderson
That, the UPS capacity, pretty much depends on what you want the UPS to do.
I installed a 1000 VA Riello Sentinel Pro, but then again its there to tide my Dual Athlon house server over power glitches and to power it during a controlled shut-down if the power is out for more than 5 minutes (yes, its overkill as things stand - it can run the server for 55 mins (it says), but a basic UPS didn't provide some of the features I wanted - controlled shut-down being one of them and, because it has 4 output sockets, I may yet make it power a few other items, such as the router, if I decide to increase the time it will power the computer to , say 30 mins.
I think you'll find the cheapies just run their loads until the batteries are almost empty and then dump the load.
My UPS has two additional features: it has an Ethernet connection and it includes a Linux daemon to monitor the UPS. You need both if you want your computer to do a controlled shut down if the power doesn't come back in time. The monitor process is what times the power outage and initiates shutdown if its configured timeout period expires. It also logs all UPS status changes, so I wrote an extension to logwatch includes these in the daily log analysis report.
It does not force a server reboot after a long outage, but that wouldn't work anyway: I have an encrypted partition, so the server prompts for an encryption password at boot time and sits at this prompt forever or until the password is entered. And in any case the server has one of those damn soft power switches which defaults to 'OFF' of the power outage is any more than the odd millisecond.
I think any PC with a mechanical power switch and that doesn't use disk encryption will simply restart by default when the power comes back minutes/hours/days after the UPS dies (no shutdown monitor) or after the monitor process (if there is one) has shut your system down.
If you just want the UPS to power an RPi plus a few low power add-ons, you might want to look at something like this:
formatting link

...but note that I have no personal experience of any RPI UPSes. Take this as a hint about the sort of thing you might look for, not a recommendation.
--
martin@   | Martin Gregorie 
gregorie. | Essex, UK 
 Click to see the full signature
Reply to
Martin Gregorie
Pi
Be aware that at low power levels some plugin monitors can be way off and non unity PF's confuses 'em even more.
Are thos figures really W (power) or Whr (energy). For sizing a UPS you really need to know the energy consumption of all the kit for the period of time you wish it to be maintained. You could have a 300 W UPS but a tiddly battery, yes it'll deliver the 300 W but maybe only for a couple of minutes.
Again power not energy is that 500W for 5 mins or 5 hours? Most UPS's of that size have 2 x 12 V, 7 Ahr batteries. Say 65 W load at 80% effciency give 80 W from the batteries. 80 W @ 24 V = 3.3 A. 7 / 3.3 = *about* 2 hours, in practice you don't want to complely drain the batteries, so real maintained time will be shorter.
Also be aware that APC have a reputation for cooking their batteries. The charge voltage is to high for float charging @ 20 C, let alone the 40 C the batteries end up at in the case with the high charge voltage. The high voltage is to shorten the recycle time when the power returns and the UPS has shut down on low battery. Trouble is the charger is "dumb" and doesn't drop back to the lower float voltage when the battery is recharged.
I'm in the middle of a long term trial of my UPS (APC Smart UPS 750) after getting at it to reduce the charge voltage and fit a fan to keep the batteries cool.
--
Cheers 
Dave.
Reply to
Dave Liquorice
Ultimately that is what happens but if the UPS can report it's status to the Pi. The Pi can decide what to do, just use a time out and "on battery" status rather than "low battery" as the shutdown trigger. Will NUT (Network UPS Tools) run on a Pi? That can certainly do that but may be a bit heavy weight.
PC's haven't had a "proper" power switch since the ATX power supply came in what 15 years ago...
"Soft switched" PCs are a bit of PITA. You can configure them to shutdown and power off and have them power up on power return. Seems OK but if the UPS doesn't drop the power to the PC it'll stay shutdown. This is a minor niggle here. I have the server switch itself off if the UPS is on battery for more than two mins, this is to extend the maintained period for the VOIP phones as much as possible. This can be the best part of an hour, if the mains comes back in that hour the UPS doesn't drop the power to the server and it doesn't restart.
There is a hardware work around involving the +5 V SB rail the normal +5 V rail and a relay. The result of me asking how to automagically resolve the problem years ago, probably over in uk.d-i-y, I've yet to impliment it as unexpected power outages are very rare so the tuit takes even longer to arrive.
--
Cheers 
Dave.
Reply to
Dave Liquorice
FWIW my Riello UPS has, AFAIK, a pair of 7Ah 21v SLAs (Sealed Leadacid Accumulators) installed. and I'm using it to run a Dual Athlon desktop PC, for which I don't have any good power consumption figures. The Riello says the batteries are reading 27v, that the UPS is supplying 0.3A at 230v and that the available run-time from the batteries is 52 minutes. That seems to show that its usable capacity is about 60 W.hours, which is in rough agreement with your battery capacity estimate.
I'm currently running it with the batteries permanently in circuit - it can be run two selectable modes (a) with the batteries continuously in circuit or (b) with the batteries kept charged on standby, ready to be switched on of the mains drops.
Interesting.
At least the Riello has a fan in it. Its currently reporting an internal temp of 35C for an internal temp in my house of 26C.
--
martin@   | Martin Gregorie 
gregorie. | Essex, UK 
 Click to see the full signature
Reply to
Martin Gregorie
To me the obvious mod would be to buy a mechanical switch (rocker or push on/push off) from Maplins, Farnell or wherever that fits in the hole left when you remove the soft switch. Use a bit of acrylic or epoxy-glass sheet to block the hole/form a mount for the switch and Bob's your auntie. Get the plastic or epoxy-board from your local friendly model shop (if you're lucky enough to have one in these degenerate times) or off eBay.
--
martin@   | Martin Gregorie 
gregorie. | Essex, UK 
 Click to see the full signature
Reply to
Martin Gregorie
normal
automagically
to
But that requires some one to be present to operate said switch. This is no different to the UPS not toggling the power if mains comes back before the UPS shuts down on low battery. Without the mains toggle the server stays shutdown rather than restarting automagically.
--
Cheers 
Dave.
Reply to
Dave Liquorice
21 V @ a nominal 2 V/cell? B-)
SLA = Sealed Lead Acid
(a) = on line (b) = off line
(a) means that the invertor etc is running all the time. Possibly not the most effcient mode with mains available but the supply from the UPS will be clean.
(b) means that the mains power is routed through the UPS, it might go via the invertors transformer with automatic tap switching to reduce or increase the mains voltage back to where it should be for the UPS output. This does mean that glitches on the mains may get through and there will be a glitch when the mains fails and the invertor has to start up. Probably more effcient and if your kit isn't bothered by the switching glitch less stress on the elecronics.
26 C *inside*. Glad I'm not there! *Far* too hot. 13 C outside and 22 inside ATM. Inside rarely gets above 23 C.
My APC UPS 750 VA is saying 45% load and 35 C internal temp. That's for two PC's and the VOIP/Router/Switch etc
--
Cheers 
Dave.
Reply to
Dave Liquorice
Said switch could just as well be the relay referred to above :) Besides, it would still need the availability of the tuit.
--
W J G
Reply to
Folderol
If you're going the D.I.Y. route have you considered pulse charging (or whatever the term is these days).
I read about it it in Wireless World in 19 mmfty mmmf.
You maintain a constant *current* charge in the region of the battery's self discharge rate, then hit it with maximum charge voltage pulses. Between these you measure the terminal voltage. As you reach the correct charged voltage you make the pulses narrower and eventually switch to a float charge.
It's supposed to give you rapid charging, less risk of gassing and an accurate measure of the actual charge state.
I think this only works for lead/acid batteries.
--
W J G
Reply to
Folderol
Sounds like a failed trial. You're doing a lot of work to retrofit product to work as it should in the first place. Time to try another brand. Just because they're popular doesn't equate to being good. I swore off APC products after I found out the hard way that their failure mode for old/dead batteries was to power off without warning. I've been using Minuteman for a while now with good success.
Reply to
Joe Beanfish
Sounds good, but way more power than I need. I'm also a bit concerned about noise, i.e., being allowed to put it in the wardrobe.
On further reflection, that's pointless; the UPS ought to keep the devices powered thorugh the flickers.
I've seen that, but AFAICT it won't power the external hard drive too.
--
Nam Sibbyllam quidem Cumis ego ipse oculis meis vidi in ampulla  
pendere, et cum illi pueri dicerent: beable beable beable; respondebat  
 Click to see the full signature
Reply to
Adam Funk
OK, obviously I'd need USB output for a Pi. 500 VA sounds way over what I need, & I'm a bit concerned about the 40 dB noise --- that's supposedly the same as a fridge, & I'm aiming to get it in the back of a wardrobe (an irregularly shaped one with plenty of air space around the equipment, not with clothes pressed up).
Not a problem!
--
They do (play, that is), and nobody gets killed, but Metallic K.O. is 
the only rock album I know where you can actually hear hurled beer 
 Click to see the full signature
Reply to
Adam Funk
Ah Ha - so its not just an RPi you want the UPS to drive. That being the case, you had best put everything on hold while you work out exactly what you need in the way of a UPS. There are several things to consider.
- the total power requirement to run everything that *has* to be operating whenever the RPi is working. This might include keyboards, mice, displays/LEDs, routers, sensors etc. as well as that external disk. MEASURE the consumption of each item so you have an accurate total power requirment.
- decide exactly how long the UPS needs to run them using only its internal batteries. This, combined with the power requirment gives the amp-hours of storage capacity you must provide. Then double it to allow for UPS efficiency and battery deterioration.
- last but not least, decide whether the RPi and associated kit needs to know if/when the mains power goes off and when it returns. If it does need to know instead of simply falling over when the UPS is drained, you need to work out exactly what it needs to be told and how you are going to pass this information to it.
Then, and only then, when you know the UPS power output requirement, its required storage capacity and the way it will tell the RPi about changes to its status, you'll be able to select a UPS that can do the job.
=====
I did exactly what I outlined above: the reason I ended up with a larger and more expensive UPS than I initially thought I needed was because I decided that a controlled shutdown was an essential, but that passing state information to the system it protects isn't something that the lesser UPSes can do.
--
martin@   | Martin Gregorie 
gregorie. | Essex, UK 
 Click to see the full signature
Reply to
Martin Gregorie
Measuring is OK as a check, but if want reliability you have to know the worst case, which might not be easy find out.
With small systems it might be possible to run everything directly from batteries and chargers. (When I ran my VCR on 500W (nominal) UPS system with built in battery I found that the 3 to 15 Watt load was dominated by the load of the inverter in the UPS, so 45 minutes was the max run time, even though 6 hours of recording over a few days would have been possible with a 10 times as expensive low load inverter made for off the grid living.)
On the other hand, Verizon FiOS used to turn off internet after a few minutes when running off its internal battery, so you would need a UPS for situations like that.
Reply to
Mark F
His original post was clear about that.
Reply to
Rob Morley
There is another (completely different) approach you can take if you like messing about with electronics (which presumably you do if you're playing with a RasPi).
Use an Arduino to monitor the battery state via one of it's analogue inputs and then perform charge/discharge management. With the addition of a very a low value series resistor or two and CMOS op-amps you could also do current monitoring.
Power it from the battery via a modern small DC-DC converter and you'll only draw about 10mA in 'standby'. The RasPi and all the other kit can be driven by a combination of such converters thus avoiding the inefficiency (and danger) of a mains voltage inverter.
This will be more expensive than an off-the-shelf unit, but probably not by a great amount, and far more satisfying to build :)
--
W J G
Reply to
Folderol
I guess the thing that bugs me the most about UPSs is that they all (AFAICT) assume you want 230 V AC, so they have an inverter. All the devices I'm interested in protecting are powered by wall warts with DC output. (I haven't checked that they all have the same output, but I suspect that all of them are 5 V DC.) Some power & a lot of components & cost are wasted in running an inverter to supply a bunch of transformers & rectifiers.
Why hasn't anyone responded to the market for this sort of set-up?
--
All crime is due to incorrect breathing. 
                 --- Sir Henry Rawlinson
Reply to
Adam Funk
They have: you'll find them on the specialist RPi vendor websites, e.g. ModMyPi.
I suspect the reason you won't find what you want anywhere else is that UPS aren't common anyway (where do you find 240v ones outside data centres and places running specialist fault-tolerant kit.
Now consider that the RPi and other small systems such as the Beagleboard are a tiny market compared with mains powered kit. Of these, the RPi has the lion's share of the market, so it follows that about the only place you'll find a UPS suitable for an RPi-based system is in an RPi accessory shop.
--
martin@   | Martin Gregorie 
gregorie. | Essex, UK 
 Click to see the full signature
Reply to
Martin Gregorie

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.