My first experience running off batteries during power outage:

[Delmar]

My attempts to talk neighbors and friends into buying at least a SMALL solar/battery power box, like a Jackery or Bluetti, or even a cheap generator, have been mostly useless.

I hate using anything with an ICE. I have a plugin electric mower and battery string trimmer. Not because I am green, but because I am lazy to maintain and fight to get started after not using for months.

I could easily purchase a small generator to recharge the golf cart batteries that power my inverter. However is difficult to justify something you may never use. Plus find space to store, and listen to during an outage.

I even designed portable generators for Generac in the mid 80’s. Sacrilege.

 

[GXMnow]

My Coleman 5000 watt generator is probably 25 years old now. Back north of Chicago it saved us through several power failures. A few times it was running as many as 4 homes refrigerators. Just this past winter I had to put a new carb on it because I forgot to put StaBil in the gas and it varnished up. I tried to clean it out, but the new one on Amazon was just $12. The new gasket set was abut the same. It is back to starting in one pull again. It was a pretty loud beast, but I added a muffler from a Dodge Omni so the exhaust is silent. The mechanical noise is not quiet, but it's not too bad. I am installing an outlet for it to connect to the GEN input on my new Schneider XW=Pro. So if we do run the batteries down without enough sun, it can charge the batteries. In theory, I could set it to charge at up to 100 amps and then gen should take it. That would fully charge my pack in about 3 hours. It claims 5 hours of run time, so it would not even use a full tank. At about 2,000 watts it ran for over 8 hours. I had the neighbors who were running off of it fill the tank so my power was free during a 5 day outage. Gasoline is still one of the best ways to store a lot of energy. And if an engine is running right, it really is not that bad on the environment. Maybe I will add a catalytic converter. They have small ones for motorcycles now.

 

[Hedges]

I've been on batteries and PV all day today.
Noticed the lights didn't come on in garage this morning and investigated. Inverter putting out 5 kW (plus whatever PV on an overcast day.)
Must have just happened; I was running electric furnace off batteries and they were still at a high SoC. I flipped the switch to gas heat.

Afternoon, PG&E showed up and said the transformer in vault had gone bad. They had the new one with them but encountered something they wanted to deal with before installing it (mention of mud in the bottom.)
So I'm still running on batteries. Turned off excess loads (yard lighting) for the night. I should make it to sunup no problem and batteries will recharge again.

 

[GXMnow]

Glad to hear your system worked as intended. You certainly came out better than what my system did on the power shut off last week. I am thinking about trying another power fail test, but I should probably wait until I get the Enphase firmware update. I am running on a different grid profile now, but still nervous that my microinverters will go offline from the switch over. The Schneider worked great, and did power my loads from the battery bank without a problem, but even with good sun, I only had one panel helping to power the house, the other 15 were locked out. That under 200 watts was not even noticeable as I was watching my battery drain. Had to turn off a lot to ensure it would make it through the night. Used the generator for a bit to run the fridge and a 600 watt charger directly into the battery bank. Trying to feed the Schneider XW-Pro from the generator was a problem that I did not expect.

I recently had to overhaul my old Coleman generator and installed new new carb. The linkage on the new carburetor is a little different, and it was not holding RPM steady enough for the Schneider inverter to stay connected. Without load, I got it fairly steady at 60.5 hz. With the 600 watt charger, it was still pretty steady at 59-60 hz and it would qualify as good power. Then the XW would connect the load to it, and it would flutter a bit, the frequency moved around too much and it would disconnect and go back to battery power. After the fact, I did find settings to adjust the frequency window while on generator. It is currently set to 55 hz to 63 hz. I think it was falling to 52 or so by the sound of it. My frequency counter updates a little too slow so I don't think I saw the limits. It may have dipped even lower. The short arm on the carb was making it slam the throttle plate nearly full open, then back to the idle stop. Hoping I can figure that one out.

 

[Hedges]

Mechanical control loop of the governor. Tuning of the engine. How rapid a transition of load by XW. How quickly XW disconnects when volts or Hz out of spec. I've had engines surge, and got better behavior after playing with idle and main jet. Maybe dampener on throttle would help (alter those PID terms)

DC coupling with a battery charger is one brute-force solution.

I would like generator fed through a GT inverter, so it is integrated like my PV sources. Would want a soft-connect so rectified AC doesn't see inverter's input capacitors as zero impedance. Normally the caps charge up at constant current from PV.

 

[Hedges]

I've been on batteries and PV all day today.

Late at night PG&E was working under portable lights.
I left garage fridge loads and yard lights off. Remembered to turn of tube amp in the evening.
Neighbor's lights came on during the night. I let my system run as a test.
Gas furnace ran its fan in the evening, and from about 4:00 AM. Coffee maker warmed up around 6:00 AM.
After sun came up I checked state of system. Sunny Island said batteries 33% SoC (67% DoD, 3% away from load-shed of the house).
PV panels were starting to deliver about 1.5kW on an overcast morning. Battery showed 50.4V with 2kW charge (PV output fluctuating with clouds)

I checked line voltage and reconnected garage loads to grid. Just for fun I'm leaving the house off-grid, will let PV recharge batteries rather than grid and observe how it behaves. Weather isn't bad, expect batteries to reach 0.2C charge rate before long, enter absorption after 3 hours of that.
PV production will be getting curtailed. Maybe I'll switch to electric heat from PV when I estimate that's covered by surplus production.
(SI frequency between 61 Hz and 62 Hz indicates how much curtailed, and Sunny Boy display shows how much output at that % or Hz. Except one of them, SWR2500, which doesn't curtail.)

Looks like I came within 3% of not having espresso this morning, and would have had to use a spark lighter for my new/old stove with electronic ignitor.

Eventual plan is system state controlling selection of electric vs. gas heat and shedding loads such as A/C, refrigeration, laundry, water heater depending on time of day, state of charge, grid/offgrid. Also a status indicator so I'm aware. Yesterday I was using electric heat from battery power for a while until I tried to turn on a light in the garage and realized grid was down.

 

[Hedges]

Sun's out at 10:30 AM.
SI reports 5.0 kW charge at 57.2V, 58% SoC (of 20 kWh bank)
That's 87A, about what I programmed (85A, I think, for about 0.2C)
Frequency is 61.72 Hz, indicating 72% curtailment, 28% of available PV being delivered.
Sunny Boys report 5800W, so 5kW to battery and 800W to house.
? I don't have quite that much PV! ? 5.8kW is 28% of 20.7kW

I turned on electric heat.
Frequency dropped to 59 Hz (request full power from PV, also correct accumulated error in any electric clocks)
Sunny Boys show 7.2 kW (SWR2500 will remain offline due to low frequency)
SI reports 2.8 kW output at 50.4V, 58% SoC, boost phase, 2 hours remaining for charge (maybe that's 2 hours absorption after boost complete?)

Looks like PV + battery are putting out 10 kW for electric heat.
That 72% curtailment of PV estimate is way off. More like 72% of available production. Maybe the linear ramp from 61 Hz to 62 Hz isn't accurately implemented by SB. But the functionality works fine, even if not linear.

Turned thermostat down so electric heat is off for a while. After battery gets full it can kick on.

Optimum system would ramp up discretionary loads from 60.5 Hz to 61 Hz, so battery charging first, then loads are enabled first before PV gets curtailed by SB. For that I would like a PF corrected (1.0 PF) controller that delivers variable voltage sine wave output depending on frequency of line, for resistive loads. Variable speed of pumps and A/C or heatpump can be achieved with VFD. Someone with a mini-split might be able to make a PID control of thermostat setting so it consumes only surplus PV generation. I don't know if any of those are PF corrected.

 

[EricBarbour]

running central electric heat from inverters? either you're crazy or you're severe-duty-testing them.....i would not do this unless someone paid me

 

[Hedges]

running central electric heat from inverters? either you're crazy or you're severe-duty-testing them.....i would not do this unless someone paid me

I am crazy ? , but that's another story. I have a 10kW electric duct heater and my 4x SI 6048US can deliver 23kW continuous, so they weren't even breaking a sweat.

An annoyance with the US model Sunny Island is that the 56A relay at 120V doesn't let much more power through from the grid (or from Sunny Boy to the grid) than the inverter's power rating. It was developed for Europe, where at 230V the same relay could carry 12.8 kW.

When I bought my first one retail for $5000, I was going to use a 120/240V transformer and a transfer switch. Thanks to Warren Buffet (and others) providing $1 Billion to DC Solar, I picked up several SI 6048US for cheap, and have configured them 2s2p. More for the higher current transfer switch than for the wattage output. My battery can run them full load for just 20 minutes.

My intention is to have Sunny Island and Sunny Boy pick up the house load when grid fails, but not power electric heat, just the gas furnace fan. Laundry and A/C can run so long as PV is charging, SoC is high. If I pulled more wires so duct heater went direct to grid, that part would be taken care of. I need to pull data cable to control relays switching the other loads based on SoC and other status signals. But for the time being, duct heater is wired through the Sunny Island relays. If I hadn't caught it, after an hour or so the house would have disconnected and I'd have had to wait for an hour or two of sunshine to get batteries back to 50% SoC.

Once my batteries were full and PV production was up to about the consumption of the electric heater, I switched it back on to observe operation for a while before reconnecting to grid.

I want to get all these things working automatically, for instance shedding dryer heating element (but not control/motor) and A/C at perhaps 80% SoC. Ideally, loads would be continuously varied based on frequency shift to maintain 100% SoC.