DIY Tesla power wall - how feasible is this?

Handruin

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I watched this video the other day and made me wonder how feasible this DIY project is and if this guy is really way off his rocker in terms of making a feasible battery wall similar to what Tesla offers? There are all kinds of questions I have that aren't answered in this video and maybe some with more experience (like jtr) can shed some light?

I'm curious if it's really feasible to buy up and test used battery packs on the cheap and salvage good cells? Even if you pick through and find 600 good cells, how reliable will they actually be over time? What kind of electronics are needed if any to ensure there aren't temperature issues? Is this a non-issue with protected 18650 cells? The video page has links to the parts used in this but I'm still skeptical about it. He has some other videos I'm going to check out about how to assemble the packs and test the cells.

 

ddrueding

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I've been watching this guy for a couple weeks now. He seems to have a good-enough grasp on what he is talking about. Of course, the big money thing not mentioned here is that neither his (nor the Tesla) include the inverter that would be required to make it work with your house.

Going through old cells (breaking them out of laptop packs, etc) and testing them will only go so far. That can answer a few things (capacity, voltage at full, voltage at empty, sag under load) at the moment, but longevity you can only guess at by comparing the current capacity/voltage to optimal.

Here are the real-deal battery packs from Tesla cars. Used of course. I am closer than I should be to planning a conversion of my car to electric.
 

LunarMist

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Will the State Farm pay if the home burns down?
It doesn't seem like the best idea.
 

ddrueding

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Each of the cells is individually fused, so that helps. Metal box is a good idea. Clear of the house is a better idea. I'm currently putting together a garden shed with solar panels, battery array, and inverter for off-grid use. We'll see how it does.
 

LunarMist

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Each of the cells is individually fused, so that helps. Metal box is a good idea. Clear of the house is a better idea. I'm currently putting together a garden shed with solar panels, battery array, and inverter for off-grid use. We'll see how it does.
But do you need secondary lithium battery packs outdoors? I'd rather go with lead for short-term UPS power and then have a generator for longer run times and reliability.
 

ddrueding

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I'm going with a deep-cycle lead for my current project. The draw and charge are going to be slow enough compared to the capacity of the pack, and the weight and size of the box will be mostly irrelevant. Well, it will matter to a few people on the day they deploy it, but I'm going to be standing back with a hardhat and clipboard ;)
 

Handruin

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Are you able to share more the project you're working on? Sounds interesting to have a small off the grid shed in the back yard.
 

mubs

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Man, those inverter batteries weigh a ton. IIRC, ~ 65-70 pounds each. The ones I had previously (before I moved to my current location a few years ago) came with think rope handles to carry / transport them. Two grown men strained to lift one battery, and I had two!
 

ddrueding

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Are you able to share more the project you're working on? Sounds interesting to have a small off the grid shed in the back yard.
This one isn't for the back yard. I need to relay a wireless signal into a canyon we're going to start mining. Most open mines are built into the back side of hills so you can't see them from the main valley, this makes line of sight from our other facilities difficult. I've had a plastic garden shed (this one) modified with an interior and exterior aluminum frame. The interior frame supports batteries, 2 deep and 4 wide about 4" above the bottom, and the mounting board for electronics (half-sheet of plywood for screwing stuff into). The exterior frame includes the racking for the solar panels (4x 200W, side-by-side in portrait mode at a 45-degree angle along the back of the shed), the radio mast (14' high, 3" pipe), the floor skid for staking it down, and the hoist brackets for lifting with a helicopter. Interior frame is 1.5" thin-wall square tubing, exterior frame is 2"x4" thick-wall tubing.

The helicopter I have access to can't lift it all at once, so there will need to be a second temporary frame to transport the batteries separately. I've used the drone to construct a full 3D map of the area (~6" accuracy), and have a pretty good idea where I'm going to put it. Of course, putting stuff on top of a hill that we'll be removing has its challenges.
 

Handruin

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That does sound really neat, I'll be interested to hear how it all goes for you. That's a fun and interesting project to work on. Are you relaying an internet signal using one of those long-range wifi units similar to ones Ubiquity sells? How long of a distance do you have to align the dishes to?
 

ddrueding

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Yup, using Ubiquiti gear. The relay down into the quarry will be a sector antenna, probably one of these, to feed the different facilities (gatehouse, scales, processing, haul trucks, etc). I'm currently evaluating different options to get data in there. Ideally it would be a direct feed from the 85' tower at our main facility using AirFiber5, but that is ~16 miles and directly over a city with 250,000 people (interference much?). More likely I'll send it up to the local radio tower (4 miles in the other direction) where a local wireless ISP has internet and just do a VPN.
 

Handruin

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Yup, using Ubiquiti gear. The relay down into the quarry will be a sector antenna, probably one of these, to feed the different facilities (gatehouse, scales, processing, haul trucks, etc). I'm currently evaluating different options to get data in there. Ideally it would be a direct feed from the 85' tower at our main facility using AirFiber5, but that is ~16 miles and directly over a city with 250,000 people (interference much?). More likely I'll send it up to the local radio tower (4 miles in the other direction) where a local wireless ISP has internet and just do a VPN.
Is this location out of range of an LTE wireless and/or are the speeds not feasible for so many different devices or is that what you're describing with the local radio tower?
 

ddrueding

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Is this location out of range of an LTE wireless and/or are the speeds not feasible for so many different devices or is that what you're describing with the local radio tower?
Speed might be ok but the bandwidth would be too expensive for the security camera streams. Razzolink is a local wireless ISP that I have a really good relationship with. They have 500Mbps+ of internet at the top of a local hill and would let me buy some. I've attached images of both runs for perspective.

Home Run.jpgLocal.jpg
 

snowhiker

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If you are able, post some pics of the setup when complete. Sounds pretty cool.
 

Tea

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Amazing project Dave!

Back to the home power theme, lithium is way too fashionable. It's not by any means the be-all and end-all of battery techs for anything that isn't portable. LEad-acid is looking like a much better liong term tech, given the huge advances being made, the looming shortage of reasonably priced lithium, and it doesn't explode! (Not so long as you don't go silly with charge rates.)
 

ddrueding

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Indeed. It seems that Lead-acid or flooded batteries are the better option. And as always, having more capacity is good for a bunch of reasons.

1. Charge/discharge rate per battery is lower for any power level
2. Charge level is easier to maintain away from extremes (batteries don't like being >80% or <20%, IIRC)
3. Fluctuation in daily charge amount can be averaged

At the moment I'm just running 4 batteries to get to the 48-volt I need to directly drive PoE devices. Might be ramping up the capacity depending on what I can get from the panels.
 

Tea

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If I remember correctly, lead-acid batteries are less efficient at ^80% - you get less charge per unit of input. On the othrr hand, they degrade rapidly because of crystsl formation on the electrodes at lower charge ratios, and of course they really hate going below 20-odd percent. Several new technologies are coming onto the market to allow long life despite operating in the middle charge region. This strikes me as a game changer (for stationary batteries only, of course.)

(Please excuse typos. Either I'm practicing to be Lunar when I grow up, or else I'm borrowing Tannin's new toy. You decide which sounds more likley.)
 

LunarMist

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If I remember correctly, lead-acid batteries are less efficient at ^80% - you get less charge per unit of input. On the othrr hand, they degrade rapidly because of crystsl formation on the electrodes at lower charge ratios, and of course they really hate going below 20-odd percent. Several new technologies are coming onto the market to allow long life despite operating in the middle charge region. This strikes me as a game changer (for stationary batteries only, of course.)

(Please excuse typos. Either I'm practicing to be Lunar when I grow up, or else I'm borrowing Tannin's new toy. You decide which sounds more likley.)
The major advantage of lead acid batteries is the low cost and wide varieties of systems available.
 
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