UPS and Generators sometimes don't play well together

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Dave V

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Neighbor
Joined
Dec 22, 2020
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270
Location
Florida
Before when we had inconsistent power, all computers were on UPSs.
We learned the hard way that during power outages, even though the UPSs were in place to keep the computers up until the generators kicked in, the generator harmonics would trick the UPSs into thinking there was STILL no power, so they would remain on (and beeping!) until the batteries died and then the computers would shut off anyway! This is WITH the generator supplying power!

We solved this problem by getting "better" UPSs (we had to test them all with a generator to find the brands/models that worked!) Then we went to all Double Conversion UPSs that filter and convert incoming utility generator power to DC, then invert the DC to sinewave AC for our equipment. (WAY more expensive but less expensive than cleaning up the generator outputs.)
Now-a-days, with laptops so much more powerful, we have no more "tower" workstations. The laptop batteries protect control room computers just fine without a UPS. The servers still use big UPSs, and they are all Double Conversion.

Really though, no UPS has ever been activated since we went 100% solar powered (for several years now)...i.e. all power is inverted except grid power, which we haven't used in quite a while. Even power from the generators is run through the inverters. We still have grid as a back-up, and duel fuel generators: piped natural gas (more reliable and unlimited while avalable!) and tanked propane (cheaper, on-site, but limited.) Testing it all each month is a pain, but not my pain!

Speaking of batteries (UPSs,) we've replaced all of our AGM battery banks and now use only LiFePo4.
Their life is supposed to be 15 to 20 years, but we keep one rolly cabinet of them (literally weighs 1000 pounds) in storage. The point of one rack in storage is that in case one of our 48V batteries fails, the whole bank could be replaced and then we'd immediately order replacements for our back-up set.
I am told the back-up set has really held their charges well. On Oct 1st, after two whole years in storage, the back-up LiFePo4s are at 74% (down from 100%) after 2 years in storage. I think they were brought back up to 100% at that point, but it's good to know they keep their charge so well in storage. The idea in storage is that they are not being cycled at all, so they get older, but aren't being cycled. We already have a waiting list of members who want a "bad bank" of batteries for their home solar set ups if/when we rotate a set. Chances are, removing the one bad battery from the bank will give them a fully functional bank minus only a couple of KW-Hours. Yes, we could just replace the bad battery at the facility, but supposedly each battery in a bank should have the same "wear" else it causes some problem...now I should just shut up and find out why rather say something out of ignorance. Anyway, it's interesting stuff and I'm pleased to still be around to see it!
 

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