Generator kicked on

Wed night about 11:30, my backup propane generator kicked on. I went out to the solar shed and the SOC was 81%. The generator is programmed to come on when the batteries get down to 50%. After a half hour or so it turned off. I checked the batteries and they were now 80%, so it wasn't charging the system. The next day while flipping through my read outs, it said "last generator use - April 23". That's the day they tested it. Why did it come on? It has been getting down to 19-20 degrees at night. Does it come on occasionally to charge the generator battery?
12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)
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KID #51B 4s 140W to 24V 900Ah C&D AGM
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West Chilcotin, BC, Canada
Most gensets seem to assume that they are "backup" to AC main power, and use an AC battery charger or expect the genset to be exercised every 1-2 weeks to keep the genset starter battery charged. If your genset still started after 7 months of not running--Sure sounds like it is getting charged somehow.
-Bill
Once while I was gone it got down to 69%. That's the lowest so far.
I am a bit confused that even if this was a monthly exercise, that it did not appear to charge the battery bank during that time. You may have a fault somewhere.
A suggested, fuel efficient, running schedule would be to start the genset at 50% State of Charge and run it up to 80% SOC. That would be the most fuel efficient program and relatively easy on the batteries. Batteries are there to be used.
As always, you should measure the specific gravity once in a while to confirm your SOC estimates (from charge controllers, battery monitors, etc.). SOC readings from meters are not always accurate.
-Bill
Hi, check your AGS setup sometimes my generator will come on because I have reached an amperage setpoint say for instance 30A. Maybe your load had reached that setpoint. My guess, by the way you should exercise your generator every week or so you can set that up at your AGS or on the generator control. The battery gets charged by the feeders you have connected to the generator terminal strip, can't remember the #s now but can look it up. I don't think the generator will charge its own battery while running, it is charged from the house panel.
Still
We've had a few cloudy days and the SOC only got up to 69% today. I'll be surprised if the genny doesn't come on tonight.
-Bill
10% of 740 AH = 74 Amp charge rate
74 amps * 59 volts charging = 4,366 Watts -- fare amount of power (not including AC charger losses, generator deratings and such)
-Bill
Fix driver error with calculator...
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
You are balancing fuel cost and battery life. It is the reason a well designed solar system in a good location will have long battery life without a generator.
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