Review on 🔌 Reliable and Versatile Liebert PSI5 UPS - 1500VA 1350W 120V 1U: Rack Mount Line Interactive AVR Sine Wave UPS with Surge Protection and 0.9 Power Factor by Keith Aluguvelli

I have installed this UPS in a rack and so far it is working fine. I was expecting to be able to just plug it into my Linux system via USB and control it with NUT (Network UPS Tools). However, this UPS is not supported by NUT. Argh. In case you're wondering, it uses a removable 48V, 5Ah/240Wh LiFePO battery. Big, but not that big: my $150 "solar generator" (which can be used as a UPS in a pinch) has a capacity of 333Wh (it's LiFePO if you're wondering), it's still going to be heavy . AVR functions work, However, allow the voltage to vary widely (at least +/- 15V) before changing the windings of the transformer to compensate. My old AVR UPS had much more precise control (keeping voltage within +/- 10V). Don't be fooled by the name "PSI5" and the expansion port on the back, this device cannot be configured with runtime expansion. Battery pack (not that it was ever advertised as supporting it). I fell for this train of thought, although I thought I had done enough research beforehand (read wrong datasheet). It turns out that none of the lithium-ion versions of the PSI5 series support external batteries (which makes sense, but I was still hoping). If you remove the expansion port cover, you will see that there is no connector inside. My UPS was shipped to me with the battery attached, which struck me as odd. But everything works. It arrived with 60% charge. Was it really worth the extra cost? May be. I'm still a little annoyed that it's not supported by the UPS Network Tools (NUT), but maybe that's about to change.