Building my own pseudo(Powerwall)

[L-P-G]

Alright, it's been a while I have done lots of stuff but have been slacking on updating the thread. So here's almost a month of updates

Since I switched to using the pack chassis as my "shelf" to mount the packs I had to figure out a way to mount the bus bars to the chassis itself. I bought some battery standoffs but for the life of me I couldn't find any M6 threaded rod locally. Luckily the bolts on the pack are pretty long so that gave me an idea.

Put the bolt on a vise, add a couple nuts (you'll see why later) then cut off the head and ta-da, instant threaded rod.

The reason for the nuts (other than to hold the bolt on the vise without damaging the threads, is to unscrew one over the area where the head was cut to fix any damaged threads during the cut.

Add some red thread locker and they're all done.

Back on the AC side I got the ATS wired and the loads panel connected to it.

Then came time to wire up the Inverter, since the ATS in the inverter can handle 19kW I calculated a #3 THHN (@60C) but the connectors on the inverter not only were too small but also didn't allow proper torque, So I ended up removing them and connecting directly to the breakers where the connectors were attached to.

This makes me glad I re-wired the thing. This is how the neutral output came from factory.

Then came time to run the wires to the inverter, 7 runs of #3, I thought it was going to be a pain, but with a little pull lube it went like a glove. (you can also see the bus bars temporarily mounted, I didn't take any pictures of marking the holes and drilling them out)

Finally here's all the wiring connected to the inverter through the knockout I made on the side of the inverter.

Since the AC side was all done I needed to get the DC buttoned up, the negative side wasn't getting a fuse I decided to mount the bar directly to the batteries by fabricating some Z bends out of the left over bus bars I had (I had purchased some stacking battery straps from EVTV to wire the modules together but since switching over to using the chassis I couldn't use those anymore. On a side note getting a return from them is a PITA but that's another story)

I had to mount my vise to the garage floor because I was literally tipping over my workbench.

All done Z bars bent, just needed to drill some holes in them.

For the positive side, I wanted the ability to disconnect a module from the pack without removing the whole bus bar. So I reused from of the EXRAD 2/0 cable that I ripped out of the pack since it's apparently rated to over 1000A.

What do you do when your hydraulic crimper takes a *sugar* on you and no one locally sells lug crimpers? You improvise.

It took a bit longer longer using the vise but I got them all done.

Here are the bus bars all cleaned up and heat shrunk to prevent accidental shorts.

Here's how the negatives are connected to the bus bar (this may change since I noticed that a module could easily be shorted while connecting the opposite module, I may add fuses on the negative as well just in case)

On the positive the fuse holder is attached to the bus bar, then a 200A bussman fuse is in the between them protecting each module. The other benefit to mounting the modules to the busbars with a double layer of material is that I get to maintain the electrical capacity of the bar since now the material is thicker, this makes up for the mounting holes in the busbar.

For the past couple days I've been testing the pack/inverter and it's capability to sustain the house loads and I'm happy to report that I haven't ran into any major issues.

The first day I turned on the system and failed the house over to the pack I thought I had caused a brown out that damaged the AC compressor capacitor. In the end I just had to have patience since the manual failover caused the compressor to shut off inadvertently the Ecobee was doing a 300 second delay to allow cool down before starting it.
I've ran the house on the battery from the moment I got up to night time (I work from home) and I used about 25% and I didn't even have all 14 modules connected (only 8). So I think when I AC couple battery capacity won't be a problem, It looks like it would take a few days of no sunlight whatsoever to fully drain the pack.

Here's where the battery sat that evening. kWh is on the green side because the battery is charging back up using the internal charger from the grid. (I still need to AC couple my solar into the ATS panel, it's rained every damn day this month)

I also modified some of the Grafana dashboards to display the most relevant information in a prettier format.

Although the inverter can handle the LRA of my compressor it does cause the lights to blip and my UPSs to beep. Call me crazy but I'd rather not induce brown outs when possible. This led me down the hell hole that I call HVAC companies.
I must have called at least 6 HVAC local suppliers who all told me:

"Sorry we can't sell to home owners"

That *sugar* annoys the ever living *sugar* out of me, even more when I call a contractor to get it done since they're running this nice little monopoly and they don't even know what I'm talking about.
I finally got fed up and ended up buying it online from a marine distributor in Miami, Since soft starts are used in RVs and boats it seems they carry them and don't mind actually selling the products they carry, go figure.

Since I'm currently not AC coupled, and sometimes (like at night) I won't be I wanted to be able to control the internal charger on the inverter, I can use the EVTV BMS controller control the bottom end and disconnect the battery if it gets below my set threshold but the top end I can't do since the BMS controller disconnects the battery from the inverter and won't reconnect it without a human touch it means it would leave the pack disconnected if I had the BMS controller not set to the same top end SOC as the inverter.
Secondly the inverter seems to want to use fully charge (4.2V per cell) and discharge (3V per cell) the pack which is not what I want since lithium doesn't like to fully charge and fully discharge.

So knowing I could control the bottom end with the BMS and the AC coupled charging using the BMS, all I had left was to control the grid tied charger built into the inverter. Here's when I had to get custom, since the inverter doesn't have an interface I had to go poking to see what I could find. Luckily I found that if i set the battery type rotary knob to 0 it would disable the grid tied charger (9 is lithium).

Once I had the board out of the inverter I proceeded to map the rotary dip switch contacts when set to 0 or 9.

Since it had to visible part numbers I couldn't pull up a spec sheet so I used a trusty multi meter in diode mode to figure out the connections, after scratching off some of the comformal coating I found out that connecting 2 pins to the common was the equivalent of setting the dial to 9. This means I can leave the dial always on 0 and use a micro controller and relay to turn on and off the charger according to the battery SOC.

I used some shielded cable I had to solder some connections to the board

This also opens the door to StormWatch mode when using the NOAA API

API Web Service

So after a very long post that's where I stand. The pack works, the inverter switches to battery mode fine, I have plenty of capacity (way more than 2 PWs would have given me), I can run just about every load (except large concurrent loads like my S charging at full amps and the dryer but I can move my 14-50 to grid only or lower the charging amps on the car and who runs the dryer during a power outage anyways).

Now it's just final details on controllers and some custom software to control it all, oh and AC coupling my solar which isn't a big deal.

I'll post some more as I get more stuff finished.

 

[rebel1996]

Ok, this is an awesome build. I bought the 15kW version from EVTV and have planned to build something similar. Would you be able to share a rough budget? I only have a <1000 watt solar setup and a $550/month Duke Energy power bill. I was going to buy a 22kVa propane generator but decided to go the solar+power wall with a small generator to charge the batteries in an extended outage.

 

[L-P-G]

Ok, this is an awesome build. I bought the 15kW version from EVTV and have planned to build something similar. Would you be able to share a rough budget? I only have a <1000 watt solar setup and a $550/month Duke Energy power bill. I was going to buy a 22kVa propane generator but decided to go the solar+power wall with a small generator to charge the batteries in an extended outage.

I put a few redundancies into my system to ensure if something went wrong I could easily switch sources and get power back, I'm also putting extra hardware in to use a web dashboard to control the hardware so my cost is a bit higher.

But for core costs:
-The battery itself was about $11k. You can buy just a few modules off ebay and keep this cost down.

-The inverter was $2500

-The evtv bms controller and cables for the bms modules was about $2800 (you don't exactly need this as the inverter has a lithium profile BUT if you want your pack as it's healthiest for things like balancing and safety cut offs you're going to need something to balance the cells and cut off power to the pack in case of over or under voltage, you couke remove the Tesla bms modules and use a cheap bms instead along with a victron protect (keep in mind this won't get you stats on the battery unless you get a bms with uart port but even then you'll have to write some custom software to capture stats as the evtv controller does all of the above and comes with control software already)

-Depending on your setup you can skip the ats panel and save about $500, everything else will vary based on your setup since it's mostly cabling and accessories like line splices and conduit.

-I wanted the pack to use as little space as possible since I only have a 2 car garage, so there was some cost on this as well to reuse the pack chassis, fabricate some custom busbars and get them mounted but if you just stacked your modules and used some pre-made stacking busbars to keep the tooling cost down as well.

Let me me know if you have any more questions.

 

[L-P-G]

@dennis_d Have you tried out the serial port on the Sigineer? I'm getting no communication on mine when I plug a a DB9 cable into it

 

[dennis_d]

you need to buy SNMP card to talk to it SNMP Card Web Management Accessory For Online Monitoring of Inverter

 

[L-P-G]

you need to buy SNMP card to talk to it SNMP Card Web Management Accessory For Online Monitoring of Inverter

Only if you want to conver the serial port into SNMP traps and alerts. The card just communicates over RS232 to the inverter.

See doc below for the commands you can send via the DB9 port.
https://www.sigineer.com/wp-content...verter-Charger-RS232-Communicate-Protocol.pdf

 

[L-P-G]

Awesome. Looking forward to hearing how this works out. That's a lot cheaper than a Magnum or Radian.

I was doing some web browsing and found another inverter that looks better.

Quattro - Victron Energy

The highest variant is 15kW and it'll do AC coupling with freq shifting as well. It also looks to have a ton more features and much better support than the Chinese Sigineer.

If my Sigineer goes out that will be my replacement as long as I can find their UL listing.

 

[miimura]

I was doing some web browsing and found another inverter that looks better.

Quattro - Victron Energy

The highest variant is 15kW and it'll do AC coupling with freq shifting as well. It also looks to have a ton more features and much better support than the Chinese Sigineer.

If my Sigineer goes out that will be my replacement as long as I can find their UL listing.

As far as I know, the Victron Quattro line does not have native split phase. You have to either stack two 120V units and live with the limits of each inverter on each side of the neutral, or you have to configure a 230V unit as 240V and use an autotransformer to bind the neutral and get the split phase 120V. As a point of comparison, the Tesla Powerwall inverter can support 100% imbalance on split phase.

 

[Ulmo]

13kW is my absolute peak and it's not maintained for long, their way the house maintains a constant usage of 1-1.5kW so I should be ok. Worst case scenario since my solar is using micro inverters I have multiple branches of AC, I was thinking I can put a contactor on one of them and drop a branch for X amount of minutes to avoid an overload. (I need to see if I can do this from the Envoy)

Ok, look into that. In days with more sun power than direct sunlight power, you will get more than solar panel peak rated power for minutes at a time.

This happens to me on some lightly cloudy days (about 2 to 3 times per year, most often after a rain on a mostly sunny day): the solar panels get both direct sunlight and indirect sunlight lensed into it, and it swings back and forth between about 1.3 times solar panel rating and .7 times rating. While the average is near the full rating, the peaks last for minutes at a time. It's fun seeing 6800 watts coming out of my inverter on a 5800 watt peak solar system that usually only gets about 4500 watts peak in a day; the last time this happened was August 18, and I stood there for many minutes watching over 6800 watts (I can tell when this happens, because I can feel and see brighter-than-full-sun light outside, and whenever that happens, I run outside and look at the clouds then run inside and look at the inverter output; it usually happens when the clouds are light and lensing like a hologram or magnifying glass). My SolarEdge inverter is rated for I think 8600 watts, so it happily obliges, and my 2 PowerWalls easily suck up that energy since it's under their 10kW continuous input capability, and the grid happily takes any overages.

I'm looking at my stats for August 18. It had peaks above 7,000 watts of solar into the Tesla Gateway starting at 13:20:43 and ending at 15:03:12. http://ulmo.solar/powerflow/2019/08/18.png Here is that linked pic and some zoom ins I made to show up close:

5800 peak system (21 panels at 280 watts each is 5,880 watts):

Note that monitoring.solaredge.com does not show those peaks, only the averages, and it's lower on that day than usual:

Tesla App shows some of the peaks above the solar panel system rating, but not as high resolution as my graphs:

For comparison, a usual day: http://ulmo.solar/powerflow/2019/08/20.png

 

[rebel1996]

Thanks for the excellent details. I love the way you can toggle the 0 or 9 setting to disable the charger. I think I need to buy the EVTV BMS at some point, but I want to get the basic system working with 2 model S modules just to confirm the basic stuff. I see the load panel and ATS module you are using, that’s a great setup. Do you have a basic line drawing for how the inverter is wired in relationship to the utility meter and your homes regular panels? I am trying to figure out if I can just put the system off a 50A or 90A 2 pole or if I need to have power from the meter flow through the unit and all the house panels fed off the inverter. I have some grid-tie micro inverters, but only 1000 watts. I don’t have a net meter and don’t want to feed upstream (I assume my smart meter won’t run backwards)

 

[rebel1996]

I built similar setup using 8 Tesla modules and 15 KW Sigineer inverter. I don't use frequency shift but have contractors on AC side that control grid connection and switching between battery and grid if needed (do have manual bypass switch just in case). View attachment 413743

Do you have a drawing on your setup? I have the 15kW model from EVTV and I’m trying to determine where/if I need a transfer or bypass and where to tie in the inverter. I want this to function as a whole house UPS/generator for the frequent Duke Energy Florida outages (less than 2 hours typically) and for hurricanes. I bought a 12kW dual fuel generator than I wanna use for extended outages to recharge the batteries, plus some solar via grid tie micro inverters.

 

[L-P-G]

Ok, look into that. In days with more sun power than direct sunlight power, you will get more than solar panel peak rated power for minutes at a time.

This happens to me on some lightly cloudy days (about 2 to 3 times per year, most often after a rain on a mostly sunny day): the solar panels get both direct sunlight and indirect sunlight lensed into it, and it swings back and forth between about 1.3 times solar panel rating and .7 times rating. While the average is near the full rating, the peaks last for minutes at a time. It's fun seeing 6800 watts coming out of my inverter on a 5800 watt peak solar system that usually only gets about 4500 watts peak in a day; the last time this happened was August 18, and I stood there for many minutes watching over 6800 watts (I can tell when this happens, because I can feel and see brighter-than-full-sun light outside, and whenever that happens, I run outside and look at the clouds then run inside and look at the inverter output; it usually happens when the clouds are light and lensing like a hologram or magnifying glass). My SolarEdge inverter is rated for I think 8600 watts, so it happily obliges, and my 2 PowerWalls easily suck up that energy since it's under their 10kW continuous input capability, and the grid happily takes any overages.

View attachment 448459View attachment 448460

I'm a bit behind on updates to this thread but so far I've gotten my solar AC coupled and everything is working fine. Today being the first day after Dorian the sky was just about cloudless and I was able to test the max output of the solar going into the pack.

The inverter and pack were able to take about 12kW of AC (less on the pic due to AC->DC losses). However, at one point the AC solar jumped to 13kW and the inverter took it fine, but it did light up the overload LED, no alarm went off though (I think the manual states that once the audible alarm is heard then the inverter is not happy).

Either way I solved that issue by just turning down the AC, I figured may as well use the power to cool the house rather than waste it by turning off a branch of micros. I plan on setting up an API connection to the ecobee and as a secondary in case internet is out the water heater using a contactor and MQTT. Talk about first world problems because I'm generating too much power.

I've also gotten a bit further on my custom control dashboard where I can control charging, take the house off the grid, etc. I have run into an issue that the Rpi I was using for this doesn't have enough resources so it looks like I'll be moving it to a VM.

Do you have a drawing on your setup? I have the 15kW model from EVTV and I’m trying to determine where/if I need a transfer or bypass and where to tie in the inverter. I want this to function as a whole house UPS/generator for the frequent Duke Energy Florida outages (less than 2 hours typically) and for hurricanes. I bought a 12kW dual fuel generator than I wanna use for extended outages to recharge the batteries, plus some solar via grid tie micro inverters.

The very first post/picture is an SLD of the whole system. Technically you don't need an ATS or bypass since the inverter has its own ATS BUT if you need to take the inverter offline for maintenance or something fails on it you'll be without power. Let me know if the SLD on the first post doesn't make sense.

 

[L-P-G]

Thanks for the excellent details. I love the way you can toggle the 0 or 9 setting to disable the charger. I think I need to buy the EVTV BMS at some point, but I want to get the basic system working with 2 model S modules just to confirm the basic stuff. I see the load panel and ATS module you are using, that’s a great setup. Do you have a basic line drawing for how the inverter is wired in relationship to the utility meter and your homes regular panels? I am trying to figure out if I can just put the system off a 50A or 90A 2 pole or if I need to have power from the meter flow through the unit and all the house panels fed off the inverter. I have some grid-tie micro inverters, but only 1000 watts. I don’t have a net meter and don’t want to feed upstream (I assume my smart meter won’t run backwards)

There's also a SimpBMS controller that works with Model S modules but it doesn't come with the contactors or the pre-charge resistor and you have to put it together, it is however A LOT cheaper.

How is your system currently wired? Do you have a diagram?

 

[Fat Bao]

Can we please see that transfer switch in action. Or a picture of it on on the battery side. I really wonder how it works.

 

[rebel1996]

Hey, I live in the Orlando area, (Oviedo specifically) and I wonder if you give tours of your build. Maybe on Halloween. I just bought a Model 3 performance and don’t have a breaker position for a wall charger, and I still haven’t unboxed my 15kW inverter. I am sort of hung up on the bypass. I love that ATS one you bought and found it on Amazon, but I can’t figure out how it lets you route all the load THROUGH the inverter.

Hate to be a bother, but your setup is exactly what I had sort of planned, but i don’t want to tie up so much of my garage and I need to sort out the wall space and new panels.

 

[Xianrecords]

This is a fantastic post. I like the external ATS implementation. Indeed, the inverter has its own ATS but I believe it is limited in term of AMPS that can go through in pass thru mode. Does anyone know what is the limit on the 15KW Inverter ? Also, have you thought of automating the ATS with some sort of programmable relay (with a Rasperry PI controller) that would allow you to take the system on and off grid based on time of the day or other parameters ? In the area I live PG&E offers discount grid price based on the time of the day.

 

[L-P-G]

Can we please see that transfer switch in action. Or a picture of it on on the battery side. I really wonder how it works.

Working on it, I just finished some software and now the external ATS is my next goal.

Hey, I live in the Orlando area, (Oviedo specifically) and I wonder if you give tours of your build. Maybe on Halloween. I just bought a Model 3 performance and don’t have a breaker position for a wall charger, and I still haven’t unboxed my 15kW inverter. I am sort of hung up on the bypass. I love that ATS one you bought and found it on Amazon, but I can’t figure out how it lets you route all the load THROUGH the inverter.

Hate to be a bother, but your setup is exactly what I had sort of planned, but i don’t want to tie up so much of my garage and I need to sort out the wall space and new panels.

Shoot me a PM.

This is a fantastic post. I like the external ATS implementation. Indeed, the inverter has its own ATS but I believe it is limited in term of AMPS that can go through in pass thru mode. Does anyone know what is the limit on the 15KW Inverter ? Also, have you thought of automating the ATS with some sort of programmable relay (with a Rasperry PI controller) that would allow you to take the system on and off grid based on time of the day or other parameters ? In the area I live PG&E offers discount grid price based on the time of the day.

Both the 12 and 15kW inverters have the same ATS which can bypass 19kW. Since I don't have a standby generator to control the external ATS a RPi is exactly how I plan on controlling it. I already figured out that it uses 12v and the ATS switches when -12v is applied to the trigger pin, it'll stay on gen mode until -12v is removed. I just need to get some relays and a 12v source mounted in the box. At the moment I manually switch the panel ATS but I have control over the grid feed to the inverter ATS so I can easily go off grid by using my control GUI.

When I'm done the GUI will also have a "Bypass" mode which will bypass the PW and connect the house directly to the grid.

 

[Xianrecords]

Very Cool. What external ATS are you or do you plan to use ?

 

[Xianrecords]

Never mind - Saw the reference in an earlier post. Tx

 

[L-P-G]

The internal ATS inside the inverter cannot be controlled externally. (Well the remote has an RS232 port but I haven't been able to get any data in or out of it, doc attached) To get around the issue and be able to switch between battery and grid mode while not in panel bypass I installed an 80A contactor which is controlled by my RPi controller GUI.

https://d2mkuqdfjd17yj.cloudfront.n...CONNECTION-for-Online-Monitoring-20190124.pdf

https://www.sigineer.com/wp-content...verter-Charger-RS232-Communicate-Protocol.pdf