[time-nuts] UPS for my time rack

Poul-Henning Kamp phk at phk.freebsd.dk
Sat Oct 10 10:14:02 EDT 2015

In message <1444483218108.6a07c91c at Nodemailer>, "Chris Waldrup" writes:

>Has anyone had bad experience noise wise with the APC brand units
>like are available on Amazon and at Staples? I'd like to get one
>that doesn't generate lots of RFI. Thank you. 

Then don't.

Instead get 12 or 24 Volt sealed lead-acid batteries and a good
float-charger, and run your stuff from that.

You avoid a lot of conversion losses, and you get to decide what
quality batteries you want (As opposed to "the cheapest we can get
away with") and you get to decide how long hold-up time you want.

The important tricks are:

  1. ATO Fuse *RIGHT NEXT TO THE BATTERY*.  Not a meter away, but
     quite literally bolted right onto the terminal.

  2. Don't buy a shit charger, it will cost you battery life.

  3. Suitably sized fuse/polyfuses on all loads.

  4. Either put 0.010 Ohm current shunts in all over the place
     or buy a 1mA resolution clamp meter and prepare the wiring
     for measurement.

And that's it really...

I run all the always-on stuff in my lab from two 12V/105Ah telco-grade
sealed lead-acid batteries, and I'll never look back.

Presenty the load is 6.7A @ 24V, and that powers my ADSL lines,
firewalls (soekris), home server (ITX with mini-box.com PSU),
emergency lights (LED strips), GPS, GPSDO, HP5065 etc. etc.

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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