[time-nuts] UPS for my time rack

[Tim Shoppa]

A winning way to do 12v and 24v wiring up to 45Amps are Anderson Powerpole
connectors. Many sources sell fused distribution panels.

For larger currents (up to 350A) the SB "Storage Battery" series is broadly
used in Forklifts and solar applications

Tim N3QE

On Tuesday, October 13, 2015, Poul-Henning Kamp <phk at phk.freebsd.dk
<javascript:_e(%7B%7D,'cvml','phk at phk.freebsd.dk');>> wrote:

> --------
> In message <4FD0F30EBAEF49609DF207E3EE61C15B at pc52>, "Tom Van Baak" writes:
>
>
> >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.
>
> 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 at 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.
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