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My Powerwall Project
#1
Hello Everyone I am new here,
I have been lurking in the shadows for some time and reading posts, watching videos, and taking as much information in as I can. This group seems to be very knowledgeable and I am excited to join the community. I especially like "HB powerwalls" on youtube, I bought one of his shirts to support him and have seen all of his videos I will donate more when I have some extra funds as I really enjoy his stuff.

My goals simply put: To stop paying for electricity entirely, and send small amounts back to my utility company (utility connection is .35 cents (US) per day regardless of usage) to zero out my bill. I would also like to convert my car to electric power (I am a master mechanic for my profession) and install electric vehicle charging station into my home. These are my long term goals. With these 3 main goals in mind, I would also like to do this project with as many cheap if not free materials as possible, I will get more into this later.

That being said I already have 15x 315W Longi Mono solar panels, 15x p320 SolarEdge optimizers, 1x SolarEdge storedge Se-3800A inverter, and an LG Chem 9.8Kwh battery. This system is about 3 months old and I love the system, but after watching the company install the system I realized I could have installed it myself. Also, after 3 months of monitoring and watching I am still paying a power bill. So I installed an "Emporia Vue" smart energy monitor and I am now watching my power consumption in real time through my utility companies meter. Although I realize this may not be entirely accurate, it is reporting to me the numbers the power company will use to determine my bill, thus this is the number I am interested in. I attached a rough drawing of my average daily power usage.

So far I have decided to build an 18650 based powerwall. I have started by going on batteryhookup and ordered 900 cells to start. I also ordered 2x 8 cell charger / capacity testers based off some recommendations on here. The chargers are to arrive today and cells next week, I will begin tear down and cell processing immediately, however I do not plan on having a fully working powerwall for several months if not closer to beginning of 2021.

In addition to ordering the 18650 cells to begin processing, I have also decided I want to place my powerwall in some type of enclosure. I am unsure of my local regulations, so I purchased a copy of NFPA-111 which is my local fire code and regulations pertaining specifically to energy storage, photovoltaic power sources, and electric vehicle charging. I also need to check and see if I need to acquire permits for my area (most likely as I am in southern California US) for the energy storage, I know I will need new / additional permits to install any more solar panels.

I was able to up-cycle several old cabinets that I am hoping to store the powerwall inside of, they are "UL" listed meaning it is rated for electrical components. After determining if they will work (reading the NFPA-111) I plan on rubberizing the inside of the cabinets, mounting them to the back side of my garage, and painting the outside the color of the house (of course leaving warning labels visible).

Looking around, I also found that I have a large surplus of metal clothes hangars. They are 2mm squared steel wire which is the same as a 12 awg wire. It seems to be this would be good for 25amps per strand? I tried twisting some together and found that I can twist a pair together pretty easily, 3 or 4 is rather difficult especially without kinking. The other issue I have with this is that some of them break while twisting, leading me to believe I could have some porous sections of this conductor which would create a hot spot and possible an open circuit. So, if I continue through with this idea, I plan on testing each individual bus bar by actually flowing amperage for extended time (like 10 minutes or more at 150% of the amps I plan to run through it) and then check for hot spots using thermal imaging. Due to the materials, I would need to test each individual bus bar prior to service, meaning this would be extremely time consuming but would cost nearly nothing and leave me with peace of mind.

I have yet to make any decisions as to battery pack configuration with 2 exceptions, I like the fuse wire to each individual cell, and I want to run a 48v system.

I am posting this to log my progress, as well as receive any input. I appreciate any and all help. Thank you everyone for taking the time to read my post!

Grizwald
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#2
Hanger wires are made from cheap metal. this is why you get ones that will break. If you keep the amps low (much lower than equivalent sized copper) then you *might* not have an issue. But, I think over time you'll develop one. Also, clothswire usually has a coating on them to help keep them from rusting as they have iron in them. So may make soldering to quite difficult.

All in all, copper wire is pretty cheap and you only have to work it once, not possibly several times. I would recommend forgoing the hanger wire and just get some house wire and strip it.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
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#3
Korishan Wrote:Hanger wires are made from cheap metal. this is why you get ones that will break. If you keep the amps low (much lower than equivalent sized copper) then you *might* not have an issue. But, I think over time you'll develop one. Also, clothswire usually has a coating on them to help keep them from rusting as they have iron in them.  So may make soldering to quite difficult.

All in all, copper wire is pretty cheap and you only have to work it once, not possibly several times. I would recommend forgoing the hanger wire and just get some house wire and strip it.
I went and looked at 12-2 Type NM-B with ground. Looks like all 3 twisted together should flow 50 amps easily (2x 12awg = 50 amps, plus 1x 14awg = 20 amps for total of 70, so 50 should be safe to operate at) and its 50$ (US) for 250 ft. If I haven't been able to find some for free (or cheaper) ill pick some up when I have processed enough cells to begin my packs.


P.s. Thanks for moving the thread.
Griz
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#4
Hit up an electrician friend to keep offcuts for you. Anything 1m or longer could be useful I would think. When I get closer, I'm going to do the same.

I'm harvesting tool batteries. Much longer project timeframe at a lot less cost.
-----------------------------------------------------------------------------------------------------------------------------------------------------------
As at Mid May 2020 -Total cells 1,135/Shucked 1,045/To be shucked 90/Processed 194/To be processed 608/Zero volt 183/Bad/rusted 19/Sanyos 1/21700s 24
All tool batteries comprising of Milwaukee, Makita, AEG, Hilti, with Samsung, LG, Sony and Sanyo cells from 1.3AH to 3.0AH (OEM)
Chargers... 1 x Nitecore D4/1 x LiitoKala 500/1 x iMAax B6AC
On order... 5 x LiitoKala 500/1 x LiitoKala 500/1 x iCharger 4010 Duo
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#5
Also check the local recycler. They take many forms, not just a scrap yard. We have one local here called the Repurpose Project where they are a not-for-profit organization and take in donations all the time. I've gotten several motors (even got a 5HP), pumps, electrical wire, computer psu's, wall warts, etc, etc.

And, you don't need a 250' roll. I'm sure you should be able to get a 15' roll. You could even buy by the foot from Home Depot or Lowe's or such.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
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#6
(06-26-2020, 11:56 PM)Korishan Wrote: Also check the local recycler. They take many forms, not just a scrap yard. We have one local here called the Repurpose Project where they are a not-for-profit organization and take in donations all the time. I've gotten several motors (even got a 5HP), pumps, electrical wire, computer psu's, wall warts, etc, etc.

And, you don't need a 250' roll. I'm sure you should be able to get a 15' roll. You could even buy by the foot from Home Depot or Lowe's or such.
I was able to score some free wire based off your recommendations. I asked an electrician friend and got what was left of a 100' roll, salvaged some more from a pile at work, and found some I had stashed that was left over from the solar installation. I think I am set for now, pretty good size stack.

Meanwhile I measured the inside of the cabinets at 30"x12.5"x13". I found the cell holders are 20mm per cell. So I plan to do a 14s35p battery pack x2 per cabinet side by side. This makes the battery pack approximately 11.024" by 27.5591" by 3.2"(ish). This gives me 490 cells per pack and 980 in the cabinet. My idea is 14s for "48v" and 35p to keep amperage down around 1 amp max per cell. 18650 cells have nominal voltage of 3.7v x 14s = 51.8v nominal pack voltage. 35 strings at 1 amp max each, this gives me 35 amps x 51.8v = 1813 watts per pack. 3626 watts per cabinet with the packs in parallel. 3626 watts divided by 120 volts = 30.216 amps. This means each cabinet can take 2x 15 amp circuit breakers off my house panel and should be totally safe. It also means I can run a 4000w inverter per cabinet. 4000w divided by 51.8v = 77.22 amps divided by 2 packs = 38.61 amps per pack, divided by 35 strings = 1.103 amps max per cell, good enough. This also should be perfect for my 14-2 wire which is 2x 14 awg solid core copper rated at 40 amps twisted together, and I'm going to twist the ground in as well for a 3rd wire which I believe is either 14 or 16 awg, either way it will raise my capacity on bus bar to 50+ amps and I am limiting them to 35-38.61 amps total.

I decided I would like to add some type of on / off switch and a fuse to the packs to make them slightly safer to move around from work bench to cabinet etc. I know this will increase costs unless I can find switches, but safety > cost. I am looking into BMS now. I like the idea of Batrium, especially the monitoring software, but the upfront cost is a little crazy. The simple 14s 48v 40-50A BMS on amazon / wish / ebay for 50$~ seems like a viable option and since I am not stressed for time I may go this route.

Battery charger / testers delayed shipment - estimated arrival monday and I can begin testing the 14 cells I have harvested and fully charged using a cheapo charger from my old vape pen. The 300x pegatron modem batteries are scheduled to arrive via Fedex 7-5-20. I need to order another 400x or so to complete 2 cabinets.

I like the idea of glass fuses because you can see if it actually burned or if you broke it, but it seems like excessive cost that could be avoided by using tinned 35 awg wire as fuse wire, I know both are tedious albeit the fuse wire slightly less so, not my concern at all, cost vs functionality is my only concern.

For now I plan to finish 2 cabinets, take 4 of my 15 amp circuits off the house and run them on the battery packs. Then get some type of charger/s and put it on a smart plug/s that I already have and am not using. This way I can set charge time to when I am producing excess power from my existing solar system. Then discharge batteries overnight instead of drawing power from the grid. I have a decent ATS already as well for this. Later down the road I plan to add additional solar panels and MPPT charger etc, this is simply a work around while I ramp up my project.
Korishan likes this post
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#7
So I was at work today and I walked by this cardboard box, it was very weathered but I saw the corner of a battery sticking out. I opened the box and found 3x 2kw 12s "48v" Chevrolet volt modules and 1x 1kw 6s "24v" module from a first generation volt. Now I work at the local dealer, these things have a core on them and are normally impossible to get your hands on from the dealership itself. This one had clearly been sitting some time. Out of curiosity I opened the black plastic case next to the above mentioned battery and found a second generation volt module sitting there consisting of 2x 2.3kw 12s 48v modules. I went and inquired with the parts manager and he said hes been trying to get rid of them but it is difficult. I told him I wanted them for a powerwall and he told me I could have them!! Big Grin 

So I brought them back to my work area, pulled the covers off and measured the voltage. Also, because I just like to have a bit of fun, and because I want to keep track of my individual modules health / storage etc. I will be naming them all different names, but not numbers, that's not fun, plenty of other numbers here.
Prescilla found at 42.5v - sat outside inside the decrepit box with duct tape over the terminals, I touched my meter across the battery over the duct tape when I first found the battery, it was 150 something volts DC just sitting there.... no fuse....) for 2+ years this is a gen 1 module, rescued 6-29-20
Elvis found at 42.6v - same as above
Sher found at 42.6v - same as above
Sonny found at 21.3v - same as above
June found at 47.6v - sat outside inside a black plastic case (could be problematic due to temperature)2+ years gen 2, rescued 6-29-20
Johnny found at 47.6v - same as above

Couple other updates, I decided on some 40$ each BMS from ebay / ali-express etc w/ "UART" which is Rs485 communication. I have a spare computer that I will be installing Linux server or similar onto and connecting a series of BMS to. This will collect data and I plan to collect that data from my server and put it into some type of GUI (graphics user interface) like Grafana which is an open source free client. I decided on this because it is modular where each individual battery will have its own control and adjustable settings etc for specific batteries such as Chevy volt batteries and my 18650 power wall. Now the interesting and fun part will be figuring out some of this code to get the server to properly ping my BMS'. 

On another side note, I have been looking at power inverters from 48vdc to 120v ac 60hz. I see a generic one a lot of you have from ebay. Its a black case with a green sticker on it that says "pure sine wave inverter" and specifies voltage etc on the sticker. You all seem to be happy so I will be buying this brand. However, check my math on this... 
4kw inverter surge 8kw 445$ each @ 1, or 436$ each @ 2+.
10kw inverter surge 16kw 1,340$ each (what I would need for my whole house)

So if I bought 3x 4kw @ 436$ thats 1308$ and would give me 3x4kw @ 12kw constant and 3x8kw 24kw surge.
Its cheaper to buy smaller ones and get slightly more output? not to mention, if I bought one unit and it fails, the whole house is down, with multiple units it creates a failsafe depending on how its all wired, or at the very least I wont lose everything no matter how its wired. The other thing about this is the fact that the 4kw inverter will fit inside the cabinet with the two battery packs.

Although I think this will result in a very clean install, it will create thermal issues and therefore create efficiency issues if not safety issues. So my current plan to remedy this is to put a divider down the center of the cabinet effectively splitting it in half and sealed at the bottom, open at the top (divider is open at the top, inside the cabinet). Then place inlet fan on bottom right of cabinet, outlet fan on bottom left of cabinet. This will draw air in the right side, flow up the right side of the cabinet and crossover at the top then draw air back down the left side of the cabinet and finally exhausting out the bottom. Fans will likely be powered from some type of buck converter and likely attached to a temperature sensor of some kind attached to inverter for on / off.

I began researching chargers for the volt modules today as well. Most likely I will get something that can talk on rs485 or reports to a cloud. I found a bunch of MPPT solar and hybrid chargers that I can adjust settings on, this will be extremely important to have 2 separate units to charge my 18650 wall at 58.8v~ and my Volt modules at 50.4V~. But I still want them to talk to each other and to my server. Having similar / same chargers with different settings will make the coding / pinging process much simpler later on when I go to integrate all this information to Grafana.

If you made it this far, good job. Sorry for being long winded, but again I am using this as a type of blog as well, I want to record my build progress here and I hope some of the detailed information helps some of you out there. 

P.s. @ HBpowerwall I subscribed to your Patreon, I found myself with a few extra bucks after my huge score today Smile
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#8
Awesome! Free batteries! That's a great deal.

As far as code compliance: I too, am in California and it depends on what electric code your local housing authority has implemented. We haven't updated to the 2018/2019 NEC code. This allows me to use batteries that are not UL listed. The newest electrical code requires that the batteries specifically be UL listed for this application.

Either code requires a 5' spacing from any building or property line. I wanted to do like you and wall mount in a UL or fire box. That was not approved.
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#9
Nice score grizwald, I’m using 3 of the 2nd gen 60v Chevy volt batteries and so far working great.. I’d be interested into here about how u hook up a bms to them. Good luck
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