How do you distribute the 48/24v power? A row of fused links? circuit
breakers? That's always been the part that looks cobbled together. I
see Windstream rectifier racks with wire nuts, and wire just hanging out
in the open, and an autozone inverter sitting on a shelf, so apparently
even the Telco's don't always have good solutions.
On 6/28/2021 12:35 PM, dmmoff...@gmail.com wrote:
You already pointed out the major plus to A/C power: It's simple. Any joker
can come along and plug something in. Almost every device has a 110VAC
option.
UPS's are looking cheaper because you're getting used/refurb. You'll come
out more comparable with a new DC system compared to a new UPS with similar
runtime and capacity.
I've never had a UPS as reliable as a rectifier. A handful of failures out
of dozens over several years does not actually sound reliable at all. It's
obviously tolerable to you in your scenario, but it's not telecom
reliability. Scale that up to 100's of deployments and you'll be chasing
dead UPS's more often than you'll want to.
The good rectifier systems will be -48v because that's the standard for
telecom power. If you're in Ubiquiti/Mikrotik land you'll have to use
converters to +24V. If you're in Cisco/Juniper/Arista land then it can all
be -48v and then you don't need the converters.
I absolutely have been where you are now. If you're on a budget where what
you can afford is the used APC XL then maybe you just stick with that. DC
plant is better, but you will pay more for it and you'll pay more for the
routers and switches designed for it.
These are all statements of opinion, but it's opinion informed by 22 years
of playing this game.
-Adam
-----Original Message-----
From: AF <af-boun...@af.afmug.com> On Behalf Of Nate Burke
Sent: Monday, June 28, 2021 12:58 PM
To: Animal Farm <af@af.afmug.com>
Subject: [AFMUG] Tower UPS's (again)
We've been using the APC SmartUPS 750XL as a Tower UPS for several years.
Put 2-8 100+AH AGM Batteries on them, and they've been rock solid for us. I
can think of only a handful of failures in the dozens deployed over the last
several years. I used to source them off ebay for $50-$70 each, but they're
becoming more and more scarce. Anybody have a recommendation for a simple
UPS that will do all the monitoring that the APC does and accept big
batteries?
We're a Metro-Rural Area, our power outages are usually measured in Hours,
not days. So I'm not as concerned with the inefficiency of doing the
DC/AC/DC Conversion for Runtime, just power stability during
outages/fluctuations. I like the ease of connecting the external
batteries to the APC, since the XL line has an Anderson plug on the back for
them, and has a larger charger than the normal UPS, so recharge times are
very quick.
When the boss goes to the WISPA Shows, his head is filled with all kids of
ideas, so he want's me to investigate doing everything as a DC Plant, When I
price that out, with chargers, voltage converters (24/48), inverters, fuse
protection, LVD, Monitoring, etc, it always seems like the price is a couple
hundred dollars of parts and it would be cobbled together.
Am I missing something with doing a DC Plant? I see the telco's at the
sites using a rackmount rectifier with power supply modules, but those are a
several hundred by themselves, and they are only 48V, they don't have to
worry about 24v radios. When I build a site now, I drop in 2 batteries, and
the APC, and the site is up and running in a couple minutes. A DIN rail
with a couple power supplies and the box is done, and has fully monitored
power, and I can plug in whatever I want without any equipment
modifications.
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