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diy solar

Adding storage to my Enphase system

He had never even taken it out of the box and didn't have oil or gas for it. My son brought over a quart of oil and our gas can. He got the generator powered up for him. I also sent over an old 700 watt inverter. They got a few essentials powered up about midnight. About an hour later the power came back on. OF course, once he had backup power, he no longer needed it. They had originally predicted the power would not be up until 8 am, but it was up before 2.
 
I just put up a post in the battery section. Chevy has issued a recall on the Bolt for battery fires. They have only had 3 incidents, but they are taking it seriously. In short, I am not very concerned, but to be safe, I have lowered my maximum charge voltage. Chevy is to limit to 90% charge until they find the cause as all 3 fires were on a full charge. We all know full charge is a bit stressful on lithium batteries. I lowered my maximum voltage to just 57 even, or 4.071 volts per cell, which works out to about 85% charge. I always have been monitoring temps and have no reason to suspect anything is going on with my pack. But to be safe, I suggest anyone else using the Bolt packs to lower the max charge a bit until we know more.

I am sure I will get some "I Told You So" comments from the LFP guys.
 
My Bolt is still sitting in the garage. Just checked, no fire yet! But, I already had the charge limit set to 85%
 
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This occurred at the bottom of the real estate slump. Leveled the house (turned into toothpicks), carved major chunks out of neighboring houses. Owners of homes at the other end of the block with only minor damage said, "It's totaled!" (insurance more than resale value?)

"...began to suspect something was afoot when he noticed everything that was missing from the house."

“I saw a lot of remote controls, but no TVs,” Garza said.

When you store the TV, board the cat, move the Harley elsewhere, it begins to look suspicions. When you say, "The house burned down and my girlfriend gave me some of the insurance proceeds so I'm buying a new car", that's suspicious. Especially when you say that the week before it happens.
 
I am not aware of any currently factory produced EV that uses LFP type cells at this time. Due to the energy density, NMC and other Cobalt chemistries just give more range and performance. With decent battery management, they have proven to be very safe. The few bad car fires have been the result of crashes that rupture some of the cells and start a chain reaction. I am not worried about that in my garage, even in a bad earthquake. Even if my garage roof collapsed on it, the steel cabinet I have them in will support the flimsy roof structure. At that point, I would be more worried about the snapped off gas line. The big worry about these latest Chevy Bolt fires is that the cars were not crashed right before they burned. The one common thread is that they were just fully charged. And they may have been on a DC fast charger. The car can charge at 53 KW on a DC fast charger. At 96S near absorb voltage, that would be 403.2 volts at 131 amps. The car has 60 AH cells in a 3P configuration. So almost 44 amps per cell. This is about 0.75 C which is still below the rating from LG. I am running the cells in 6P and currently don't exceed 40 amps, or just under 0.12C charge rate. If the car was at 50% charge, and was hit with the full rated 55 KW charge, it could be as high as 150 amps. Still 0.85 C.

At maximum acceleration, the motor can draw upwards of 150 KW. That is close to 400 amps, over a 2.0 C discharge rate. Even if I maxed out my inverter, I can't even come close. 30 second surge is 12,000 watts. That is less than 215 amps. Again, I am at 6P instead of the 3P in the car. So my worst case peak discharge rate is only 0.6 C and I have never come even close to that.

What I am trying to say is that we are so much more gentle on these cells than their original use in the car. Even if there is a flaw or debris in a cell, the slow rates, the reduced charge cycle, not going over 90% etc. there should not be enough thermal or other stress movement to cause the separator to fail like that has happened in other high capacity cells. Assume there is a speck of metal debris inside a cell. If it was bouncing around in a car, and being subjected to rapid high current charge and discharge spikes and thermal swings, it could manage to cut through the separator and short out a cell. That was the result in both the Sony laptop cells and Samsung portable device fire issues.

If it was bad enough to fail at the light loads we use, with no motion involved, it likely would have happened already, and many more cars would be burning.

Let's assume a cell in my bank did short out. The voltage of that cell would drop. The BMS would disconnect, the fuse to the other bank BMS balance lead would pop, so it would be down to a 3 cell group with a short. The cells have aluminum sheets between each pair. They are held under a preload pressure. They would likely melt the tabs so just one cell is still shorted, or the current would be high enough to just burn away the debris causing the short. There is a very small likely hood of it going into thermal runaway to any cells beyond the initial shorted 3. And in most cases, a shorted cells get hot and vents the gases, but rarely actually burns. With my old RC LiPo batteries, I was only able to get a visible fire when I punctured a cell with a decent charge left. And even then, it had to pierce into the cell stack inside and cause a short to draw current. Just letting in air, or just shorting the cell leads never caused a fire. I have tested this on about a dozen old LiPo cells. NMC is much safer than those old RC LiPo packs.

I will keep an eye on the news and if Chevy does end up showing a bad problem, I will look into new cells. I made sure my BMS is capable of handling other chemistries without a problem. My goal is to get at least 5 years out of these cells. And 10 years is possible at my use rates. I want them to live longer than my brother's Chevy Bolt ;-) And with all of the new EV's coming out soon, I should have a wide selection to choose from when the time comes for new batteries.
 
Most people say an LFP cell just will not catch fire or burn. I can't say for sure about an external flame ignition source, but from any kind of over load, overcharge, and even cell rupture, I have never seen an LFP start a fire. They will get hot and make smoke and smell bad, but the basic chemistry is not inherently flammable. If I have found a deal even close to what I got my LG NMC pack for, I would have dome LFP. I almost bought 32 180 AH cells off of AliExpress. That would have been virtually the same capacity as what I have now, but it would have cost about double what I got these for. It also would have taken up over double the volume and nearly double the weight as well. The size and weight are not a huge deal when it is sitting on the garage floor, but the shipping cost and the space may still be a concern. Obviously for an electric car, that is a huge problem. The cost is getting better. They now have 260 AH cells for about what I was seeing the 180's for a few months back. My target was to get over 300 AH at 48 volts for under $4,000 in raw cells. I was quoted $5,200 for the 32 180 AH cells 16S2P for 360 AH at 48 volts (58.4 volts at full charge). I ended up getting the 3 Chevy Bolt pack modules for just $1,600 for 14S6P working out to 360 AH at 48 volts nominal (58.8 at full charge). The only drawback to these cells is that they are NMC which includes some Cobalt which does make them able to go into thermal runaway and catch fire if something goes very wrong.

In the real world, it does take something pretty bad for it to happen, and for the cost difference, I am willing to take the risk. The only way I have gotten a LiPo pouch cell to emit fire was by either a huge overcharge, or puncturing a charged cell and shorting the plates inside. At that point, they do get vey hot and start spewing a torch like fire out of the rupture. If it hits the next cell, it can cause the next one to burst and burn and so on down the pack. If the charge or load current is removed before exceeding voltage limits, and the cell is not torn open, it is very unlikely it will burn. But that recall on the Bolt has got me watching the pack a bit closer. My guess is that not only were the cars recently fast charged to full, they probably drove on a rough surface, or maybe even banged a curb etc. that allowed something in the battery pack to internally short out a cell. Until I know for sure, I will keep my eye on things. I also lowered my high temp cut a bit to give me an earlier warning if anything is getting hot.
 
I assumed the EV crash fires were from a release of energy. So I thought LFP would be just as dangerous in a crash.
But the problem you are describing isn't from a crash.
 
Even in a bad crash, an LFP may release gas and get hot, but it should not actually create any fire.

This new recall from Chevy is a bit concerning as the cars evidently started to smoke and burn while parked. It has only been 3 cars out of almost 95,000 sold world wide, but still, this is odd. I have not found if they were actually plugged in and charging, or just sitting unplugged.

So far the recall is only for the 58,000 cars assembled in the USA using battery modules assembled in South Korea. Chevy has sold over 10,000 cars in South Korea, these do not seem to be on the recall. They are also sold in Mexico, Canada, and Brazil totaling another 12,000 or so cars that are not being recalled either. That may change once they find out what caused the fires.
 
I have been keeping a close eye on my battery bank since the Chevy recall notice. No issue at all. But since I did lower my top voltage to 57 volts (4.071 volts per cell) I am running them down to about 50 volts (3.571 volts per cell) on each cycle to move my 7 KWH or so each day. This range is causing me to run through the knee in the middle of the discharge curve on the NMC cell chemistry. Here is the battery graph from Dec 5th.XWbat12-5-20.PNG
Below 52.7 volts, the cells have a very distinct curve. It is quite obvious on both the charging and discharging slopes. According to "Battery University" this is a normal character on NMC chemistry and it occurs just above the 50% charge point. That does seem about right. Since I have lowered the max charge voltage to just 57 volts, which works out to about 85% I am now pulling the pack down into this range every day. In a perfect world, my battery bank is rated at 360 AH. On the charge side, it runs a bit over 7 hours at 20.1 amps. That works out to a bit over 140 AH going into the pack to get it up to 85% charge. 360 x 0.85 = 306 AH - 140 AH = about 166 AH remaining. This is very close to what the JK BMS reports as well. 166 / 360 = 0.46 or 46% state of charge. Give or take a few percent. Here is my solar production, and my So Cal Edison power usage for the same Dec 5th day.
Enphase12-5-20.PNG
SCE12-5-20.PNG
The morning clouds did make me use a tiny bit of grid power in the 8 am hour as it started charging, but at 11 am to 1 pm I was still pushing out about 800 watts to the grid. The XW is still not tracking my solar production. With the shorter winter days, I also started to buy grid power again in the 2PM and 3PM hours, but that is basically just what the house uses, the solar was charging the battery still. The 5 hour "Mid Peak" time was the battery discharge. The battery powered everything in my home and was still exporting about 500 watts out to the grid all the way to 9 PM. After 8PM, the furnace was running as it dipped below 45 degrees outside. The blower and burner draft fans pull an extra 500 watts or so. My 3.4 sun hours on my solar panels is not quite enough to run my home off grid. To zero out the other 8.1 KWH I used, I would need about 8 more 300 watt panels. 50% more than I have now. And then I would need about 50 to 100% more battery as well, if I was to keep running that 850 watts all night to 8 am the next day. That is another 11 KWH of energy from battery during the cheapest time of use rate. At the current electric rates, I just don't see it as cost effective. The SCE web site is predicting my bill is only going to be $31 for the entire month of December. It may creep up a little, as we have a few cloudy days coming. At this point it has been pretty sunny for a cool December. My worst day this week still produced over 16 KWH's.

If I do this same calculations for the summer, my air conditioner just blows it all away. I do make close to 30 KWH a day with my same solar array, but my usage is more than double. I was pulling close to 55 KWH's a day back in June. Even with the solar doing great, I was having to buy 26 KWH a day from SCE. If I had the extra 8 solar panels.... That would theoretically drop to buying just 11 KWH a day. Saving 15 KWH a day in summer, and 8 KWH a day in winter. That is almost $1,000 a year in savings. Hmmm. 8 x 300 watt panels, racking, and 8 iQ8 inverters. What will that actually cost? As long as the extra power is all going to my sub panel and charging the battery bank, I won't be pushing more than my allowed 16 amps back to the main panel still. This might be a project for next year. Too bad the solar rebate keeps falling.
 
So far the recall is only for the 58,000 cars assembled in the USA using battery modules assembled in South Korea
LG definitely has a problem but since they have so many installations out there statistically it may be a small percentage. My ex wife leased a Hyundai Kona which also has an issue. She took it in for the recall maintenance and the next day it would not start. If and when she gets it back I suggested she only charge to 60 to 70 percent.
 
My brother and his wife both have Chevy Bolts. A 2017 and a 2019. They only got a recall notice on the 2017. It has the Gen 1 batteries. The 2019 and my 2018 dated packs are labeled as Gen 2 packs. They did set it to not exceed 90% charge but they are only parking the 2019 in the garage for now. My packs are running stone cold and working perfectly. With only 3 fires out of 58,000 sold, I would say the odds are pretty good I won't have an issue. Especially when you consider how low of power I am running, and it is not being bounced around on the road.
 
LG has come a long ways since their Lucky Goldstar days. I think they doubled their capacity from 2019 t0 2020. I think it is now over 100 GWhs. They also have a diverse product mix.
 
What a wealth of information in this thread! Just wanted to say thank you

After much research I also purchased the XW pro with the idea of self consumption/no export. All the marketing online leads you to believe this inverter along with the Conext gateway is capable of pretty much any scenario. Within minutes of setting it up, I knew it wasn't going to work out. First was the noise, anything above 3kw I could hear throughout my house (inverter in basement). Second, was inability to limit export to the grid. While I should have known better, since I knew it didn't come with CT clamps, the marketing led me to believe it somehow had the ability to monitor the grid and throttle its output accordingly.

Also went though the same issues with settings/glitches/voltage irregularities. I like the fact its firmware upgradable, but it was also frustrating as tech support seemed totally unaware of any recent changes. I felt as though I was explaining to them how it actually worked. After spending a lot of time with tech support I get the feeling this inverter was really only intended to be used as backup power in the event of a power failure. At least that's were they have put their efforts thus far.

At this point its a very expensive paperweight. I may cut my losses and sell it or use it to power my shop/charge cars with a separate solar array. If so, I will still need the ability for it to monitor the "grid" which which is my feed from the house and not feed back into it. I'm hopeful they come out with their own xanbus CT clamps. Otherwise I may go down the route you trailblazed!

My main solar array is Enphase as well, 21kw.
 
The export limiting actually will work if you put your loads on the output side of the XW-Pro. Turn on Grid Support and Load Shave. With the Solar also on the output side. While inverting, it will throttle down all the way to no output if the max Grid Sell current is set to 0 amps. Set the Load Shave to about 3 amps or so, as solar drops off, it will then only pull 3 amps, and power any additional load from the battery bank. The only real hassle is it will stop exporting when the battery drops to 0.5 volts above the recharge volts. So then it sits and won't recharge. My programmable logic controller is going to keep changing the Recharge Volts and Grid Support Volts to make it charge while the sun is up and export/invert during the peak rate time. I hope to get that working soon, learning a new programming language has been a bit slow for my 54 year old brain.
 
@GXMnow, I've been working on using the SMA Sunny Islands with 14kw Enphase for an offgrid install. Without an external grid, the SMAs don't like to keep synced beyond about 3kw and then go haywire. I've tried about a dozen enphase grid profiles, but there is something about them that the SMA doesn't like. If I use a dumb H bridge inverter, the Enphase come up fine and will produce at full amount. Have you had any issues with the XW-Pro being consistent or dropping/flickering leds?
 
Honestly, I have not run the system off grid for any real length of time. I have it connected to my main panel off of a 20 amp 240 volt split phase circuit. The output is feeding a sub panel for my "essential loads" that will get backup power. The Enphase solar is also connected in that sub panel to keep the solar operating in a power failure. I currently only have about 150 watts running on the sub panel. During the sunshine, I have it charging the battery bank up to 57 volts, 58.8 would be 100% on 14S NMC, so this is about 85% full. Then from 4pm to 9pm I have it run in "Grid Sell" mode to push 6 amps back to my main breaker panel. My power meter runs backwards, slowly, just like it does off the Enphase inverters at 1pm. For about the first hour, it is only pulling 300 watts from the battery, and it ramps up as the solar output falls to about 1,400 watts as it is limiting the "Grid Sell" power, so if the solar is pushing back more than 1,400 watts, it actually goes into shut down. That part works great. I can't notice any change or flicker in my LED lights during any phase of operation. From grid power only, Grid + Enphase, Grid + XW-Pro.

I have done 3 short "Off Grid" power fail tests. The longest was maybe 15 minutes. In all 3 tests, a couple of the Enphase iQ7's would drop offline, but the rest were running fine with no error. At one point I did have the Enphase solar producing over 2,500 watts and it was charging the battery bank at over 50 amps. I then turned on 1,000 watts of load, and saw the charge current fall to about 30 amps as expected. I did not have any LED lights connected, so I can't say how stable the power was, but my fan running and meter were not noticeably fluctuating. The frequency output was dead solid on 60.0 Hz and the voltage was holding steady at about 122 volts per leg. At that point, 3 of the iQ7 inverters were offline, which is why I was only making 2,500 watts. I top out over 3,500 watts on a good day near solar noon. The microinverters would not come back online until the light was blocked from hitting the solar panels. I was able to get to two of them and cover with a piece of hardboard. My other tests were done close to sunset, so total production was much lower, and as many as 7 panels went offline from the switchover. I was only getting 500 watts from solar. I turned on my roughly 1,000 watts of load, and saw the battery go from charging to discharging to make up the other 400 watts. Even in that mode, it was all working fine. The next morning, all of the panels came up again no problem. Enphase is looking into the issue. It seems to be a problem with the California Rule 21 frequency/watt profile. Even thought the power was completely stable, the inverters were showing "grid frequency out of range". Even after well over the 5 minute lockout, they would not come back on. Enphase said they have also been seeing this on Tesla Power Wall systems. The very odd part, is that even shutting off the AC disconnect so that the microinverters have to go to full grid fault shut off, and then connecting them back to a solid grid, the locked out inverters would still not come back. The DC input from the solar panel had to go away to reset it. That is a problem.

I took a pretty bad power glitch 2 days ago. The UPS on my PC kicked over, and the lights went full off and back on. Still less than a full second, but I would say the power was dead close to 1/2 second. 14 of my 16 Enphase inverters showed "Grid Instability" but they all continued to make power. They did not even do the 5 minute reset. The Schneider XW-Pro did not even store an error in the log. I totally expected it to do a 5 minute anti islanding, but it didn't. We had a huge rainstorm yesterday, and had no glitches at all, even with some huge lightning not too far away.

The Schneider XW series is essentially a basic dumb H bridge inverter. Over the years, the + and now the Pro versions have just added capability to the control board driving the H bridge. It measures the voltage and current at the two inputs and the inverter output. I have a socket for my generator connected to the second input, so it shows zero now. It has a 60 amp contactor to connect the input to the output, but the inverter bridge, is always connected to the output terminals. The input to the H bridge is directly connected to the battery bank terminals. The output side of the H bridge goes to the primary winding of a HUGE toroid transformer. The transformer is fully isolated so the core has to handle the full 6,800 watts of the inverter. I would not be shocked if the transformer alone is a solid 80 pounds, or more than half the weight of the entire inverter. The secondary windings are 2 separate coils. Default mode has them in series to make the split phase, but they can be changed to a parallel config for 120 volt only output. It is very well built with very solid components. My only complaint now is the software not allowing it to switch back to charge from AC on it's own. The high pitched wind out of it seems to have gone down quite a bit, but maybe it's because I am running a little less current and getting used to it. But I remember the whine being real bad, even at fairly low current. Oh well. I no longer cringe going into my garage.
 
What a wealth of information in this thread! Just wanted to say thank you

After much research I also purchased the XW pro with the idea of self consumption/no export. All the marketing online leads you to believe this inverter along with the Conext gateway is capable of pretty much any scenario. Within minutes of setting it up, I knew it wasn't going to work out. First was the noise, anything above 3kw I could hear throughout my house (inverter in basement). Second, was inability to limit export to the grid. While I should have known better, since I knew it didn't come with CT clamps, the marketing led me to believe it somehow had the ability to monitor the grid and throttle its output accordingly.

Also went though the same issues with settings/glitches/voltage irregularities. I like the fact its firmware upgradable, but it was also frustrating as tech support seemed totally unaware of any recent changes. I felt as though I was explaining to them how it actually worked. After spending a lot of time with tech support I get the feeling this inverter was really only intended to be used as backup power in the event of a power failure. At least that's were they have put their efforts thus far.

At this point its a very expensive paperweight. I may cut my losses and sell it or use it to power my shop/charge cars with a separate solar array. If so, I will still need the ability for it to monitor the "grid" which which is my feed from the house and not feed back into it. I'm hopeful they come out with their own xanbus CT clamps. Otherwise I may go down the route you trailblazed!

My main solar array is Enphase as well, 21kw.
I purchased the Elgris zero export controller from Germany for $240 US plus shipping ($286 total) this past September.... I like the features advertised (power source 120v, plug and play after installing CT'S)
I have tried WLAN, LAN router- repeater and even ran a 200 ft Ethernet cable to my SMA Sunny Boy 5kw-US-41 inverter from grid where the controller is mounted in a NEMA box.
The controller is talking to my inverter but I cannot get it to zero export or throttle production at all. Elgris answered one email and my 2nd one was never answered. If you look at their website (Elgrispower.com) they do large commercial productions. So tech service, probably you are on your own or should be at least skilled like GXMnow.
Their WUI has been difficult to bring up and I had an IT guy on phone walk me through Static IP to get there. I left all configuration in tact and now again I cannot bring up the imbedded web page. Maybe somehow it now has another address? 192.168.x.xxx? I will figure it out.
They sent 3 CT's (YHDC-SCT013) because most of their sales are in Europe (3 phase). We are single phase? (Split phase- 120/240) here. So I tried 2 CT's and now just one on L1 from grid. Their manual says "When the controller is used in a single-phase system the grid parameters comes from L1". Seems to be close but needs to be adjusted 2-300 watts to read properly. Again, can't view their webpage.
Lastly their instruction manual is from an older version of the energy meter which is missing some specific items to configure for the USA.
After contacting SMA tech for info regarding Zero Export, they emailed me 2 year old WattNode info. I already had that. So. no help there.
SMA Sunny Boy storage is what they want you to do. Not excited about this option.

So, that's my 2 cents for someone wanting an energy meter to view and control PV energy production...
There is WattNode (Colorado), Zed Advance (India), Elgris (Germany), Elkor WattsON (Canada) and various others by Amazon, eBay and also googling...
 
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