I don't trust UPSs for critical backup. I don't trust normal gel cells.
On the cheap, solar charge controllers make great rectifiers. They treat
the batts well and maximize your charge after a power outage. They are not
as costly as a carrier grade rectifier.
You can literally power them off of a cheap battery charger.
I am of the camp that you don't need LVDs.
You want to keep the system running until it just quits due to low voltage.
The LVD crowd says you have to save the battery. Well you really should
have a back up generator if the power is so erratic that a LVD might be
called into action more than once a year. And if it is that seldom, let it
run down. A few deep discharges is not going to kill the batt and you may
just stay online long enough for the power to come back on.
If you do want to use carrier grade rectifiers, I would go with eltek/valere
They are modular and can be found on Ebay for reasonable amounts of money.
If you do a rack with a BC-2000 you can even do battery discharge tests
remotely to check for bad cells etc. And you can have redundancy in the
charging.
Right now on Ebay, there is a whole shelf for $400 That is a killer deal.
3 rectifier modules.
-----Original Message-----
From: Nate Burke
Sent: Monday, June 28, 2021 10:57 AM
To: Animal Farm
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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