Bill Gee <[email protected]> writes: > 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.
Understood it's hard, but battery capacity is very sensitve to discharge, and I'm gueessing at what your UPS is pulling. But the point is that you did do a discharge test. > 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 ... At 3A, you're at about a 10h rate. You can look at spec sheets and find the appropriate end-of-test voltage for that rate. (For the 20h rate, it's 10.5V, almost always.) So 31 Ah for a 10h rate to 11V, means that your batteries are in great shape, probably even meeting specs. > 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 I see low at 10 and 50 warning. I don't really know how nut decides when to shutdown given your config, and I have forgotten how it decides on mine. Still, you can set up logging and get graphs of battery voltage and expected runtime during a power-fail-to-shutdown event. > 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. Just multiplying, I get 840 Wh, but you can't really get all the usable capacity out of lead acid, Between that, very high discharge rate, and <100% efficiency, getting 40 minutes would be great. > 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. Sounds like a better bet. But if others publish their protocols so that one can use BLE to get it, into home assistant, or via some proxy to nut, that's good. It's not really that bluetooth as bad, but proprietary protocols and proprietary (and very likely infested with malware) apps. _______________________________________________ Nut-upsuser mailing list [email protected] https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsuser
