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

There is an entire section in the article about how most people's first reaction is "don't burn the house down" and how the community worked together to create safety systems. The community is aware and working on issues like that

"This community takes it as a given that "email is too hard" for an amateur to do right."

I don't.

I work on software (http://www.virtualmin.com) that helps over 100,000 people manage mail servers (and web servers, and databases, etc.) for themselves. So, I disagree with the premise that email is too hard.

"Unless you're an EE and an expert in power supplies, this is way more dangerous than splicing some copper wires and following some building codes."

Is it? I don't understand how. It is a battery bank. You hook up your charge controller (two wires) and your inverter (again, two wires). Same as you would for any battery bank...it's just a better battery bank, and battery installation aint rocket surgery. (Here's a diagram: http://i.imgur.com/jXuag5l.jpg )

If one can understand a solar panel installation in the general case, it seems pretty clear that one can understand Powerwall installation. In fact, building your own battery bank is more complicated than the Powerwall, since you have to wire up all of the batteries, and figure out how to protect them from over-charging and over-discharging. Tesla provides the smarts and bundles up all of the batteries for you.

Some people like to be self-reliant and understand how things work.

Again, I can't stop Tesla from selling their products this way. It's certainly their right, and I'm still pleased with Tesla's existence (and I have a standing buy order for TSLA if it ever drops low enough, as I regret selling the TSLA I was holding a few years ago). I believe in Tesla. I just wish I could buy Tesla products and use them the way I want to.

Difference between messing with mains wiring and messing with high capacity batteries and/or solar panels is that mains always has some kind of fuse somewhere on the power company side and thus you will not see circuit that is completely unfused and will supply high currents until something blows up spectacularly and dangerously. This holds for significantly smaller things than DIY powerwall, eg. car batteries and even batteries for desktop UPSes.

Edit: for instance accidently shorting net 30 to ground when working on car electrics might well end in the car being completely destroyed by ensuing fire (I have friend who totalled his car in this way, he is licensed electrician). On new cars the fuse between 30 and 30a is usually placed directly on the battery to prevent exactly this issue, but even 30a will supply enough current to wreak havoc.

DIY projects always get glorified like this. As if people figured out this secret trick to bypass consumer capitalism. When the whole idea of capitalism is about not having to invest a ton of effort into learning a new craft every time we want to use a new product/service. We pay companies to master that craft for us with money we earn from focusing on our own individual skills.

It'd be more accurate to sell it as a rewarding experience to do as a hobby rather than a clever cost-saving commercial solution.

If money and ROI is the primary focus then most specialized knowledge could be better utilized in other ways than simply building a product once for yourself in your spare time.

Yesterday I was putzing around with these exact batteries (swapping some old tooling that had great build quality but were NiCad junk). Those 18650s pack a punch as current sources. I had an ammeter hooked up and we're talking easily in the 10s of amps for a brushed DC motor of your standard cordless Milwaukee from the 1990s.

I did the same to fix one of those $40 dollar Swiffers (i.e., we're not really talking about powering industrial steel chop-saws powering through I-beams). It drew ~2.5 amps at no-load, no problem.

OSHA[1]:

"17-90mA" : Death is possible.

"90mA+" : Death is likely.

And remember breakers blow only when the sub-circuit's current exceeds the threshold (generally ~15amps in the US) so you can spec a standard gauge of wiring sufficient to consistently draw that current, not overheat and burn your house down. It's (generally) not checking to see if the current sunk = current sourced. You need GFCIs("RCD"s in other locales) to actually get that functionality.

The rule of thumb I've heard is 50mA passing through your heart is where the v-fib dangers begin. The real risk begins at as low as 20mA, because thats when your hands lose their muscular control. You can't let go of the source, and your heart enters v-fib (~100 mA) and you get oxygen starvation and brain death[3]. You have tales of people using one hand to support themselves on a grounded breaker box, using the other hand to just have a look-see, and not even realizing they're in v-fib, feeling a little 'off', sitting down for a bit to catch their breath and found dead 20 minutes later next to the box.

Your body basically acts as a resistor in parallel with the circuit. Here's the ASME's resistance model of an adult males' body[2]. As you can see, you're body is definitely not a 10meg resistor. If you're working in damp, humid, or hot (i.e., you're perspiring through your hands, and that Na+ is just looking for a donor electron!), the risk increases. Whether you're working on a 460v3ph 15 horsepower Hardinge lathe or a Swiffer, the best piece of advice I ever got was "have a healthy respect (and fear) for your tools". Use isolation transformers, current limiters, and CAT-rated gear and read a sufficient amount of information to inform yourself in advance of the potential risks[4].

======

[1] http://web.archive.org/web/20130428070054/http://www.osha.go...

[2] http://risk.asmedigitalcollection.asme.org/article.aspx?arti...

[3] Brain death I've always heard is ~5 minutes for an average adult male with a decent pulmonary system and respiration capacity-- less if you're a couch potato with less lung VO2 capacity, more if you're Lance Armstrong. Obviously not a physician.

[4] I was googling to pick find a diagram to depict the resistance model of a human and stumbled across Allaboutcircuit's safety text (chapter 3, for those who are wondering). It's pretty good for "general" electronics. Obviously if you're working with things like tubes ('valves'), transformers, and other subsets, you're going to want to read about the safety precautions you want to take for those specific areas as well.