I have the following discharge tests: + Power-measuring plugs (I use P316M or KP115 mostly) + set of fans with known max wattages + Edison bulbs (I use 300W ones, and never exceed more than half their stated life before replacing) (only when not too hot outside) ~ set of fan heaters (must NOT be oil - those heat up. But then pause power use when the oil is hot )with known max wattages (only in winter, hahaha) - no air conditioners or dehumidifiers or anything else where parts go on and off like compressors, that alters the load.
The keys are using steady power rated-usage devices and measuring that they actually consumed it, compared to what the UPS might say. Outlet (which is also power-measuring, but I haven't used that aspect yet) <~> UPS <~> Power-monitoring plug/strip <~> rated-power device When I use a power-measuring strip, I can use multiple power-consuming devices up to the strip and UPS capacity. Since most UPS support multiple output plugs, I might have multiple plugs/strips. (Plugs usually need short extension chords, like 8 in, because the plugs can't fit side by side in the UPS usually). I had one where I plugged 10 strips in, had 60 light bulbs and fans and heaters, nearly to the maximum 1800 watts per strip, just to see if the UPS could handle it. Yes, also stood at circuit breaker, goggles, electrical fire extinguisher in hand but fortunately not needed, hahaha. Apologies in advance if everybody knew all this, but I wasn't trying to be testy, hahaha.. On Tue, Sep 8, 2026, 07:56 Bill Gee <[email protected]> wrote: > I don't have a way to do a controlled discharge at 25 amps. The best I > can do on my test jig is about 6 amps. This is mainly due to a limit on > the relay contacts which have a max rating of 10 amps DC. > > When I bought the current batteries back in February, I ran them through > my test jig using a 4 ohm load resistor and 11.0 volt cutoff. With that > they ran for a bit over 9 hours and delivered around 31 amp-hours. I > figured with a rating of 35ah that they were at least in the ball park. > Those ratings are not an exact science ... > > How do I change the shutdown to trigger at 22volts? That has to be a > NUT setting. The display on the UPS says it has 15 minutes of runtime. > A query from NUT shows variable runtime numbers in the range of about > 950 to 1100 seconds. Here is a partial dump from NUT: > > battery.charge: 100 > battery.charge.low: 10 > battery.charge.warning: 50 > battery.date: 2001/09/25 > battery.mfr.date: 2026/02/13 > battery.runtime: 1107 > battery.runtime.low: 120 > battery.type: PbAc > battery.voltage: 26.9 > battery.voltage.nominal: 24.0 > ups.beeper.status: disabled > ups.delay.shutdown: 20 > ups.firmware: 865.L5 .D > ups.firmware.aux: L5 > ups.load: 37 > ups.mfr: American Power Conversion > ups.mfr.date: 2015/06/18 > ups.model: Back-UPS RS 1500G > ups.productid: 0002 > ups.realpower.nominal: 865 > ups.serial: 3B1525X12484 > ups.status: OL > ups.test.result: No test initiated > ups.timer.reboot: 0 > ups.timer.shutdown: -1 > ups.vendorid: 051d > > Even if I can figure out a way to get these batteries to really run, the > runtime will still only be in the range of 45 minutes. An > improvement, but nothing like what a 2kwh power bank might offer. My > calculation shows that two 35ah 12 volt lead-acid batteries will store > around 400 watt-hours of energy, and might deliver only a bit more than > half of that. > > Your point about BlueTooth Disease is well taken! I agree completely. > I have an Android tablet but not a smartphone, so running that app might > not work for me anyway. Another person commented that his EcoFlow works > with recent versions of usbhid. > > ========== > Bill Gee > > On 9/8/26 8:13 AM, Greg Troxel wrote: > > Bill Gee <[email protected]> writes: > > > >> I have been getting very frustrated by the short runtime of my main > >> UPS. It is an APC BR1500G. I have a pair of 35ah batteries on it, > >> but even so it runs for only 10 minutes. The batteries are good > >> (independent testing) and the load is only 350 watts. I think the UPS > >> runtime calibration just does not work. > > > > Did the testing do a controlled discharge at 25A and measure the > > capacity to 10.5V? > > > > Change your shutdown to trigger at 22V, instead of remaining lifetime. > > I suggest logging battery voltage and claimed remaining runtime, and > > doing a test with a simulated failure, graphing that, and posting it for > > comment. > > > >> Recently I noticed that some models of Bluetti power bank, such as > >> AC200L and Fridge, have a "UPS" feature. They boast of switching time > >> under 10ms in event of a power failure on the AC mains. The energy > >> capacity is around 2kwh which should run my load for three to four > >> hours. Expansion batteries can be added. And the price is not much > >> different from a brand new 1500 VA traditional UPS. > > > > That's interesting. The first thing I checked was the battery > > technology. Units like this used to have Lithium ion and that would > > seem dangerous. This says it is LiFePO4. It claims listing to UL2743. > > > >> Has anyone used one of these as a computer UPS? > > > > not me :-) > > > >> Is there a way to have NUT monitor it? > > > > It looks like bluetooth/app, the modern disease. I would suggest > > contacting bluetti, exlaining NUT, and asking for protocol details. > > I suspect if you asked a lot the manufacturers of UL listed LiFePO4 > > power banks, one of them might end up being reasonable. > > > _______________________________________________ > Nut-upsuser mailing list > [email protected] > https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsuser >
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