I've also seen inverter systems that are designed for stand by power use in service at commercial sites in third world countries.  Within reason they basically let you run what ever reasonable arrangement of rechargeable lead acid based batteries you want that will supply the required voltage and current.  They handle the conversion of dc to ac and the switch over from commercial to inverter power.  They usually also feature a basic battery charger with settings to charge various types of batteries (ie, gel or conventional lead acid.)

Typically I've seen them used with a number of automotive style batteries.

The users would need to sort out the necessary cables, fuses, batteries, deal with safety considerations etc.

I've never seen these devices in Canada or the U.S.  Sort of a value engineered UPS system for price conscious markets.  Might be a nice starting point for those who want to role their own system and can deal with the safety aspects of this.  I'm not sure what the transfer time from utility to inverter power would be.

In the U.S. and Canada the typical practice seems to be to use packaged UPS systems that include their own batteries.

Sent from my iPhone

I'm fortunate that several of pieces of my time nuts gear (including two of my ocxo's) feature backup 24 volt dc power inputs.  They were the only things in my house that stayed running during a recent 2 day power outage while I was away.

I have two large 12 volt gel cells in series that I re charge from time to time with a power supply via a blocking diode.

I agree about the importance of the fusing.  I've also found it's easy to buy fuses rated to work on 12 and 24 volt dc systems, fuses for 48 volt and higher dc systems are harder to find.

I also bolt the fuses directly to the battery terminals.

Sent from my iPhone

On Sat, Oct 10, 2015 at 9:20 AM, Chris Waldrup kd4pbj@gmail.com wrote:

I have an inexpensive CyberPower 825 AVR UPS, The UPS does the job of
keeping my computer and time-nuts gear running, but it causes an annoying
amount of RFI in the AM broadcast band. The noise is radiated from the
circuit that feeds the UPS. I found that plugging the UPS into a Belkin
outlet strip, which presumably includes some line filtering,reduced the
interference significantly.

--

--Jim Harman

Yes this is a complex topic.  At one point in my career when I was responsible for the up time of several data centres for a high tech firm I had an Electrical Engineer on my team to (amongst other roles) work thru the various issues pertaining to UPS systems.  I recall there were significant differences between the various UPS designs.

Getting out of high tech and into an industry where data centres were out sourced was a nice change for me (:

To relate this to time nuts, those of us looking at making significant investments in this type of equipment would do well to seek out the advice of those who are knowledgable.

Sent from my iPhone

Hi

In the US, you dig those systems up either via R/V outfits or from the guys who set up big boats
(think water borne RVs rather than super tankers). The other source are the off grid solar guys.
A lot depends on just how fancy a system you are after. With reasonable effort you can pick up systems
up into the several 100 KW range.

Bob

HA! That was good. I started working at Tektronix in September 1987 and
we used VAX computers in our major field offices for order processing in
the late 80's and early 90s. They batched their daily results to our
headquarters in Oregon every night on "high speed" modems on special
phone lines. We had daily and weekly backups at each office onto open
reel tape.

The UPS horror story I can relate was at a major airline underground
computer center in the 90's. I was waiting to train a group on a high
power curve tracer they had purchased to test SCR's every time one of
their UPS inverters blew up (which must have been moderately often). I
was waiting in the supervisor's office, which had two telephones. One of
the was fire engine red, which I thought was reserved for the Hot Line
with Russia in Washington. The supervisor told me that if the red phone
rang it would be a call directly from the well-known CEO of the airline.
It seems that sometime before a worker was using a large wrench (which
was not conformally coated) directly above the critical location where
the switch between the UPS output nd city power was located. When the
wrench fell it shorted the single point of failure in their system,
stopping their reservation and flight system operation systems. So the
maintenance department suddenly received a red hotline phone for the CEO
to call when the UPS failed.

Anything can (and will) fail, and as your story about the VAX improper
manual reboot shows good intentions can turn into epic fails. When I
owned a small business in the mid-80's I was contacted by a local
company in central Texas with a small VAX and CDC disk drive who had a
major failure at his data entry company. He knew he wasn't perfroming
backups so thought it was a good time to perform preventative
maintenance on the physically large CDC removable disk pack drive (with
a huge magnet and large voice coil actuator). The company owner decided
to clean the "sock" disk drive air filter, so he removed it and vacuumed
it off.

He then made a command decision that he should use the clean side of the
filter now (since one side had been filthy) and inverted the sock filter
before reinstalling it. Gasp!! Shortly after the drive spun up a large
dust particle was sucked off the dirty side of the filter (now in the
previously clean drive chamber) and he heard a disk head bouncing around
the inside of the drive. It was (of course) the servo head. Remember
that they had no backups.

The drive was transported to CDC headquarters and they declared it a
lost cause. The small company owner asked me (and probably others) if I
would help him strap a good drive to the bad one and fabricate an arm
between the good and bad drive head acuators so the good drive servo
track would move the bad drive heads (with other required rewiring to
get the drives to work "together"). I told him NO and walked out without
wasting my time explaining how servo tracks really worked and the
mechanical and electrical engineering fallacies in this crazy scheme.
No, I would not take a penny of his money to try any portion any of that
scheme! His company soon went bankrupt, I believe.

--
Bill Byrom N5BB

On Mon, Oct 12, 2015, at 01:28 AM, Bill Hawkins wrote:

In message 1444701906.379459.408467601.5676DFA5@webmail.messagingengine.com,
Bill Byrom writes:

The interesting thing is that several sources in that business have
reported to me that about 30-40% of all power related downtime is
caused by Battery, generator and UPS failure, in that order.

Many sites simply have lower uptime after they install UPS systems.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

I found this UPS article fascinating, because it echoed what I eventually found in my own lab:

http://www.theplatform.net/2015/03/13/how-this-battery-cut-microsoft-datacenter-costs-by-a-quarter/

I used to rely on one massive UPS (along with natural gas generator) for my entire lab. Eventually I found it more reliable and convenient to have localized power backup. By local I mean backup for a single shelf, or even a single instrument.

Consider that many Rb/Cs standards and even some Qz standards have internal batteries. Even if one chooses not to use their internal batteries, most of these instruments still feature dual power inputs. In addition to power redundancy it also makes it easy to move equipment or cables around without power loss. Most importantly, local backup like this avoids the possibility of single-point lab-wide power failures.

Recently, as some of my gear works from 5 VDC, those ~2600 mAh mobile phone USB backup power bricks make an excellent mini-UPS. The ideal models are those without LEDs or on/off buttons so they discharge and charge/float seamlessly without manual intervention, even if fully drained.

Multiple units can be placed in series for additional, if slightly inefficient, capacity. A good self-test is:

http://leapsecond.com/images/perpetual-USB-power.jpg

/tvb

----- Original Message -----
From: "Poul-Henning Kamp" phk@phk.freebsd.dk
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com; "Bill Byrom" time@radio.sent.com
Sent: Monday, October 12, 2015 11:44 PM
Subject: Re: [time-nuts] UPS for my time rack

In message 4FD0F30EBAEF49609DF207E3EE61C15B@pc52, "Tom Van Baak" writes:

The big gain is avoiding the DC->AC conversions.

AC->DC conversions are covered under EnergyStar and similar programmes,
so they're generally 90% efficient or better.

But DC->AC conversions, for instance in inverters and UPS's are not
covered, the argument going that they are only run very seldomly,
and therefore capital cost would be wasted.

In the professional segment, UPS's which require a forklift,
efficiencies are good, in some cases very good, because power costs
money at that scale.

But anyting you can fit into a rack will typically have horrible
losses, the smaller the UPS the worse.  I've personally measured
sub 50% efficiency in one case.

The argument against running stuff on 12 or 24V DC is the short
circuit currents, and the absense of an affordable standarized
connector.

For the short circuit currents the only cure is fuses and caution,
and for connectors there seems to be no hope of a standard - ever.

China forced USB through as the standard for mobile phones, but
despite several valiant attempts nobody has ever managed to get
anything above 5V/5W standardized.

Here's the website of the IEEE WG which came out with a standard
(IEEE 1823:2015) this May:

http://grouper.ieee.org/groups/msc/upamd/

It will cost you $160 to see the full standard, which is a very
good and strong reason why adoption will be slow, and nobody
I've talked to expects it to go anywhere ever.

At the same time USB has come up with 100W power concept
which is not compatible, since IEEE uses CANbus and different
connectors.

I've not heard any rumours that China man nail this one.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.