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DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

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Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#111

Post by Baeocystin »

noddy1 wrote: post #70

Question.. All my device lithium batteries seem to lose ~70% of their ability to hold charge after 500-1000 cycles, however the tesla car batteries/powerwall claim to give a decade+ of use despite being built of the same cells. How does that work?

If you never discharged below ~30% or charged above ~80% of their true capacity, and made sure they always stayed within a comparatively narrow thermal envelope, your batteries would achieve the same lifespan.

The last quarter-charge in either direction is where ~80% of the lifecycle wear comes in, and temperature excursions account for much of the rest.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#112

Post by JshWright »

Reason077 wrote: post #25
hwillis wrote: post #12

Earlier quoted context omitted.

Theres no way to detonate a pack like this. 18650s have a pressure release, so the cstch fire but dont explode. In the very unlikely event that fails, a cell could burst, but it cant cause other cells to burst unless the entire pack failed to vent under extreme pressure.

Yeah. It's a total misconception that Lithium batteries can "explode". Sure, there's a fire risk if you have faulty or unprotected cells. But there's no explosion risk unless there's something very wrong with the way they're packaged.

> Sure, there's a fire risk if you have faulty or unprotected cells.

Or if an unrelated fire occurs in the garage/basement where it's located...

This is certainly enough stored energy to seriously ruin a firefighter's day if they didn't know it was there and how to properly deal with (or, more properly, to not bother dealing with it until it burns out).

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#113

Post by gambiting »

jraby3 wrote: post #86
captainmuon wrote: post #83

Earlier quoted context omitted.

Yeah but if you hack your Tesla even to change the color theme of the display, you'll probably loose warranty, loose certification status or whatever it is called (so you can't have any new parts installed unless it is expensively recertified), you'll get a call from Tesla asking what the hell you are doing, and so on. On the other hand, I can replace almost every part in my conventional car without ill effects from…

Not for long. You can still do this with older cars, but newer ones really restrict you. I just bought a new car and am not even allowed to jump start someone else's battery without risk of voiding my warranty.

I don't know what car you've got but I have a brand new Mercedes-AMG and I can do a surprising number of things with it without voiding the warranty. It's certainly as easy to work on it as on older cars, I don't need to go to the dealership to replace the brakes, the battery, the bulbs, filters, engine oil, transmission and diff oil. Manual explains how to jump start the car but certainly doesn't prohibit it. I've heard some horror stories with newer cars (especially French and American) but it's not like all new cars are horrible to work on.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#115

Post by SwellJoe »

z3t4 wrote: post #80
SwellJoe wrote: post #29

Earlier quoted context omitted.

My annoyance with Tesla is somewhat related. I don't like that I can't simply buy a Powerwall or solar roof tiles. I would have to hire one of their approved installers, which increases the cost remarkably. I don't know the markup, because you can't get flat materials pricing data from Tesla, or couldn't last time I checked, but I know labor for solar installation and electrical work is quite high. I understand why t…

Imagine the bad PR you would get when your product kills your customers.

I can go to Home Depot or Lowe's, right now, and walk out with a breaker box, conduit, a bag of breakers, a couple hundred pounds of copper, and install my own household 220V/150A electric service. Local codes or the electric company may require an electrician to sign off on my work before I grid tie, but the companies who make the stuff aren't going to refuse to sell to me. Nobody seems to think me killing myself by making mistakes with that would be the fault of Home Depot or the manufacturers, and I'm reasonably confident that is more dangerous than installing a battery box (unless Tesla has built an inherently dangerous device, in which case it won't matter who installs it).

I can also go to the same store and walk out with a roof-sized pile of roofing tiles. No one will stop me from putting on my own roof.

Hell, Tesla sells cars. The single most deadly consumer product, by far, in the world. Admittedly, people have tried to sue them about their autonomous features, but still, cars are really deadly and no one blames manufacturers for those deaths (though, we do, as a nation, impose some safety standards...but, it doesn't stop tens of thousands of deaths every year). Tesla is arguably much better about not killing their customers than some other manufacturers, but they already operate in the most deadly industry (aside from, say, coal or fossil fuels, but the deaths caused by those industries are generally an amorphous statistical blob of health problems rather than distinct deadly events).

My point is: Unless Tesla has built a dangerous product, there's no safety-related reason it should be treated differently than other home improvement items that require the same types of skills to safely install them. Electrical and solar power are well-understood by plenty of non-professionals. I do see the appeal of making it turn-key; they're aiming for average home owners, particularly at the time of construction or roof replacement, when there are already contractors involved and a mortgage to pay for everything. A large-scale solar power installation is expensive, and it makes sense for most people to work it into their mortgage.

But, it's frustrating for me; when I build a house (and I'm kinda shopping for land now in a casual way), I plan to self-fund it and do a lot of the work myself because I enjoy that sort of thing. There won't be a mortgage, and I won't be paying for contractors to do things I can do myself. Electrical work is well within my comfort zone. So, it's frustrating that when I install solar, it'll have to be the somewhat less attractive panels rather than nice-looking tiles.

It's certainly Tesla's right to sell their product however they like. But, I reckon I can complain about it, too.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#116

Post by dom0 »

snarfy wrote: post #104
Dylan16807 wrote: post #84

Earlier quoted context omitted.

High voltage, sure, but outside of an inverter that you can/should buy prepackaged none of this needs to be high voltage. The system in the embedded video has 14 sets of cells in series, meaning 40-60 volts.

How many watts are we dealing with here? What's the actual power output of a 1 second long direct short? I'm pretty sure if you shorted that 40-60 volts across a hotdog it would explode. Even if we disregard if that voltage can stop a heart (which it can, 50v is minimum), the amount of power you are dealing with is the amount of power that causes things to explode. I wouldn't go anywhere near a diy power bank without…

With batteries (and even small battery packs) there are two main safety issues: (1) chemical combustion (due to mechanical damage or stress or electrical stress i.e. over-charging) (2) Burns and fires caused by arcing.

For (2) the exact configuration basically does not matter, because generally speaking all battery packs capable of storing a large amount of energy are also able to release a large amount of energy in short time. So if you cause a short you'll always get a nice arc. Note that most kinds of protections are way too slow to suppress arcing, so you can always burn yourself. Arc-fault detection is more difficult in DC systems as well.

(1) is mostly a matter of doing things right. This means active temperature monitoring and measures (cooling, venting, shut-off) for larger packs. Independent over-voltage and over-current monitoring. And of course the little things, like wiring things up the right way and placing sense wires at the proper locations. For example, this is a simple thing of doing things wrong:

    +  Charger  -
    |           |
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |-   Cell  -|
    |           |
    +   Sense   -
Designing these kinds of circuits correctly requires a lot more experience and detail knowledge than one may think at first. (Besides miniaturization this is another reason why one-chip battery management chips are so popular in the industry).

——————

I did a few things with a few types of batteries (lithium ion and lead) and these little cells can cause an impressive amount of uh "disturbance" in short order. I admit I am almost as careful (in a different way, obviously) with them as when handling high-voltage things like the HV oscillator in an old 'scope.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#117

Post by dom0 »

princekolt wrote: post #31
Baeocystin wrote: post #4

Earlier quoted context omitted.

Kind of dangerous seems like quite the understatement, considering the nature of lithium batteries! It'd be fun to play with something like this for the learning, but I wouldn't actually run one unless it was in its own shed, many dozens of yards from the nearest anything else. Lithium fires are no joke.

I've read claims (theoretical and practical) from both sides, so apparently the safety of lithium cells can vary widely based on manufacture quality and maintenance. But also, on the video, they shows each pack of cells he uses has individual over and underchange and temperature sensors, so the system is able to tell if any individual section is going bad. It's a pretty neat, and external installation, so I don't thi…

A properly designed lithium ion pack with tested high-quality cells is a very safe thing in the environmental conditions it was designed for.

Notice how many qualifiers are used in that statement.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#118

Post by dom0 »

extr wrote: post #33
Reason077 wrote: post #25

Earlier quoted context omitted.

Yeah. It's a total misconception that Lithium batteries can "explode". Sure, there's a fire risk if you have faulty or unprotected cells. But there's no explosion risk unless there's something very wrong with the way they're packaged.

Semantics. Is a battery undergoing thermal runaway/venting "exploding"? Or merely "ejecting scorching hot gas and catching fire?" Maybe it's not blowing up like an IED, but either way I don't want it happening in my garage.

Lithium ion batteries are able to experience thermal runaway caused by internal shorts. This can be mitigated by quality control and proper handling (a lesson Samsung recently learned), and also other chemistries (like LiFePo, which is much more stable).

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#119

Post by Zak »

throwaway613834 wrote: post #77
Zak wrote: post #45

Earlier quoted context omitted.

> I'm not sure if the physical stores carry them Flashlight geek here. Several people on flashlight forums have reported finding the Westinghouse branded 18650s in physical Walmart stores. They have a low capacity - 2000 mAh, compared to 3000-3500 for the latest cells from Sony/LG/Samsung/Sanyo/Panasonic. They also use a cell of unknown manufacture, so I can't be sure of the quality. Specialty battery stores, higher-…

> Flashlight geek here. Can I ask a flashlight question? :) How do I tell how many lumens a flashlight really is? I go on Amazon and I see XyzFire flashlights that claim to give out many more lumens than would make sense, and many times they're inconsistent on the page itself. I don't know how to really tell. (If it matters, I'm trying to find a flashlight that fits in my pocket, is https://www.amazon.com/gp/product/…

You need to find a review written by an enthusiast with measuring, or at least estimating equipment. Assume all the *fire brands are outright lying. Cheap stuff claiming more than about 1500 lumens per 18650 is usually lying. There is, however a pocketable, $40 flashlight that makes an honest 4000+ lumens on a single 18650: the Emisar D4. There's a catch though: it's dissipating about 80 watts of power to do that and thermal throttling kicks in after a few seconds. To give it more HN cred, it has an open source firmware.

As to your request, a couple general recommendations first: skip the zoom, and don't chase output numbers. Zoom is pretty optically inefficient, and small zoomable flashlights don't end up with much more throw distance than similar size fixed reflector flashlights. They don't do wide-angle illumination as well either. A good reflector with sufficient output provides both at once. As for brightness, human perception of brightness is roughly logarithmic (with a base between 2 and 3), so it takes four times the output to look twice as bright. Anything over about 500 in a pocketable flashlight is pretty decent, and most 18650 lights have more.

Specific recommendation: the Wowtac/Atactical (both names show up on Amazon sometimes) A2. This is one of the smallest 18650 lights, has shortcuts to low, high and last-used modes from off and has a right-angle configuration that works equally well handheld of as a headlamp. A pocket clip, headband and 18650 battery with built-in USB charging port are included. It costs $20, and I have no idea how they make a profit given all the stuff it comes with. Go with the neutral white tint if you can find it; this looks more like sunlight and won't wash out colors as much as the cool white.

Re: DIY Powerwall Builders Are Using Recycled Laptop Batteries to Power Their Homes

#120

Post by Young_God »

There's a high risk for a house fire unless they build the power cells away from the house.

But this got me interested in my own DIY so I decided to cost compare Tesla powerwall vs DIY house fire in a box.

If I were spending $15.7k on equipment and wanted a cheaper alternative to my regular bill (~120/mo) with a 33kWh charge capacity it would have to last 10 years without any replacements to make it break even.

I could get 2x 14kWh (28kWh total) powerwalls installed by Tesla for ~$12k, with solar panels it jumps to 14k.

Note that this is price of equipment only. Installation can run up to $2k according to Tesla.

DIY: The price comes out to ~2.1kWh per $1k. (33kWh/$15.7k)

Tesla: Including $2k for solar panels, it comes out to 2kWh per $1k. (28kWh/$14k) Without solar it goes to 2.3kWh/$1k. (28kWh/$12k)

There is not much difference between the two really, except the DIY won't come with a warranty.

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