My Powerwall Project

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 ofhis 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 these3 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 about3 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 andI am nowwatching 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 clotheshangars. 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 barby actually flowingamperage 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

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.

Korishan said:

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.

Click to expand...

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 mypacks.




P.s. Thanks for moving the thread.
Griz

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.

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.

Korishan said:

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.

Click to expand...

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.

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 curiosityI 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!!

SoI 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 decrepitbox 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 asChevy 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 inverterfor on / off.

I began researching chargers for the volt modulestoday 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

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.

Nice score grizwald, Im using 3 of the 2nd gen 60v Chevy volt batteries and so far working great.. Id be interested into here about how u hook up a bms to them. Good luck

Okay, a lot has happened with my project since the last time I posted anything. So here goes an update...

The modem batteries have been completely dis-assembled and all tested. I am unhappy with the ATL cells, they are total junk and more than half appear to be leaking or corroded (white stuff around the top of the cell where the negative and positive posts are closest). They also test poorly, out of the thousand or so cells they average around 65% capacity on my "XTAR VC8" testers. The LG cells from these same packs however, I had 3 cells that have no voltage (CID is popped, all 3 came from the same modem pack) out of around 1400 cells, average capacity 108%. So I am very happy with the LG cells, but the ATL although I wasn't expecting much, were a let down.

I also purchased the "Mobius" battery packs "AveRAGE Joe" reviewed on his youtube channel, I purchased a little over a thousand of these cells. These are rated at 2900mah, so far they are testing around 50-70% capacity in total. Couple of notes, all tests are performed at a 500mA draw from 4.2v to 2.6v and charged at 250mA.

I have begun assembling packs, I started with zip ties to hold the two sides of the cell holders together but I was very unhappy with the 14s 35p configuration as the battery packs are very heavy at this size and not as rigid as I was hoping so that they would be easier to handle without flexing. So, as a result I have changed plans a little bit, I now am building a 14s15p battery modules that will all be connected in parallel. I did away with the zip ties and found some bolts from China that are the perfect size. The Allan style head and small nut fit down inside the battery cell holders and I printed some inserts on my 3d printer to distribute the pressure of the bolts across a larger surface area on the holder and it takes up a little bit of extra length on the bolt, making the bolt the perfect length (see attached photos to better understand what I am talking about!). This makes the packs MUCH more rigid and easy to move around, then I shrink wrapped my cells orange to give them a uniform look. The second issue I was having is getting the fuse wire to solder to the twisted bus bars, I am not sure if its due to a coating on my copper wires or a cheap soldering iron not getting the bus bar hot enough. At any rate, I was unhappy with this and Batteryhookup finally got their nickle cell level fused strips back in stock so I purchased 200 feet of 2p and it has since arrived.

Then we move onto the Chevy volt batteries. I have installed a BMS on each one that is bluetooth and UART communication capable and tested all 6 of the modules. The 48v modules all produced 1.7-1.9kwh and they are rated at 2kwh each, but there's an issue with the way I tested them. I did an extremely low C rate at 2 amps which improved my readings, but it was also connected to a shunt meter, then a 48v inverter and these Volt batteries are 12s configuration. So long story short, at the "end" of my test, the inverter shut off at 41.3V for all 5 48v modules, this leaves my cells at 3.441v each which leaves quite a bit left for capacity, basically what I am saying is, the batteries tested over 100% capacity at such a low C rate.

I got some work done on the cabinets as well, I went to the local hardware store and started looking at dense foam insulation and other products I thought might work well to line the inside of the cabinets and make them non-conductive and hopefully insulated / heat resistant. I found the dense foam was a little pricey for how much I needed although a good option. What I decided on is called "Hardie Backer" is a silicate based cement / fiber board. It is highly resistant to flame / heat, non conductive, fairly cheap, easy to work with, and looks okay. So I picked up a few sheets of this and began the construction of the cabinets. I also used some wood inside and although its obviously flammable, it still is non conductive and cost effective. The way the cabinets have been designed the Volt modules are locked into place in all directions, they cannot move side to side, front to back, or up / down with the designed brackets. I can fit 3x 48v modules in each cabinet making each cabinet a little over 6Kwh.

I also purchased a grid tie inverter with limiter and tested it, this works well so far and will be used in conjunction with the off grid / pure sine wave inverter setup. By doing so I will be able to use my batteries as backup power in a power outage situation but still charge them overnight at 15 cents / kwh and return it to the grid from 5-9pm on weekdays for 25-30 cents / kwh (they pay me 25-30 cents which doubles my money if you don't account for efficiency of my system).

I have also decided to install these cabinets inside my detached garage where the temperature can be more easily regulated. Recently in my backyard a couple of the temperature sensors in the garden were reading 110-124 degrees, after reading some battery degradation studies and how heat directly affects charge cycle life and capacity I opted to keep them outside of my living space for safety reasons, but still in a somewhat temperature regulated area. There is an AC unit in the garage and the walls are finished and insulated so the temperature stays below 85 at all times and is usually below 80 degrees. This makes me feel good about the charge cycle life and degradation of my batteries. That being said I'll stop typing now and post some photos.

On a side note, I found a GPS tracker that contains a .318wh battery or 85mah, they are 3.7v nominal pouch cells. I think its hilarious so I will be messing with these, I'm trying to get 14 of them at the moment to make a 58.8v battery that is about the size of my finger...

Lastly, I made a 10 pack race with modem packs. I saw HB powerwall and Average Joe did their 10 pack laptop pack race, well I wanted to do modem packs. I have since sent Average Joe some packs so that when he has time he can make a video, and I offered HB powerwall to send him some packs too, but I think hes afraid of my superior speed , anyways here's a link.

Good work.

The plain 10 pack challenge is me who have the records though but its harder with laptop packs.

This nextpicture is from Terry Nagy over at Power2spare.net... APallet of medical batteries on their way... Estimated 41kwh? Its roughly 3600x BF1's from his site.



And heres a picture of the sample I purchased from Terry already of those BF1's.



I also acquired 1500 Ring batteries from battery hookup's sale. I noticed they had over 54k in stock at one point so I know a bunch of us got some... Anyone up for a pack race? ??
All of these photos are just updates. I changed plans to go 7s14p with the extra slot for bms & possibly active balancer if they ever arrive... I find myself addicted to buying batteries and I still havent actually hooked any up yet... ?....? time to hook some up. After Terry's shipment arrives no more batteries for a while.... Maybe....

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Honda insight batteries... Definitely questionable purchase... ?





BMW 200a main contactor... Good purchase! ?





Pallet of BF1's from Terry Nagy over at Power2spare.net arrives next wednesday a week from today! ???