What does a kilowatt hour look like?
blog.kubakuzma.com
blog.kubakuzma.com
An 18650 battery, if combusted, can produce hydrofluoric acid with just water vapor in the air (or the water in your lungs) if they use lithium hexafluorophosphate as the electrolyte. Hydrofluoric acid can and will cause permanent damage to lung tissue if inhaled, and nasty, nasty chemical burns to exposed skin. 18650 batteries are supposed to have several failsafes to prevent thermal runaway, but counterfeit batteries can lack those failsafes. Not to mention, in some laptop battery packs, the protection was pack-wide, and not in individual cells. Not knowing the chemistry of the cells or the state of the protection circuitry of the battery would make me very nervous. Maybe someone else can provide more detail on how to test them safely.
Just use sealed AGM batteries, don't burn your house down or deal with spilling chemicals everywhere.
Even just drawing in parallel from batteries like this is a fire hazard. Charging is an out of your mind goal.
I'd not have known how much of a bad idea this was had I not been a long time fan of EEVBlog. It's an entirely different world when touching Lithium cells. Even drawing in parallel from cells from the same batch can be a bad idea.
I think you've confused parallel with series; in parallel, the batteries will naturally balance themselves to the same voltage and discharge proportionally to their capacity. It's the series configurations that are riskier and need extra balancing circuitry.
Also, I'm pretty sure the bulk of fires are from the much more fragile pouch "lipo" cells, not hard-cased 18650s like these. You may note the extremely large number of lipo fire videos on YouTube as evidence.
On the other hand, 18650s tend to be quite a lot more robust and difficult to ignite:
If you're building a large pack you don't want cells with a built-in protection. You connect all the cells to a pack-wide BMS that keeps things safe.
The important thing is to never use unprotected cells without some protection circuit in the pack.
Recycled 18650 cells that have worked fine in laptops for years are very unlikely to suddenly explode on you for no reason. I'd be more worried about the mystery Chinese ones you can get new on the web!
Here's some Materials Science students at Oxford who built packs using recycled laptop cells. They used controller software that monitors the health of each individual cell:
https://m.youtube.com/watch?v=RW1Xugey8j0
(It's towards the end of the vid)
It really depends on their condition. If you get some cells from a laptop and they've all fallen down to reading 1 volt, then yeah repeatedly charging them (especially at a high amperage) is going to be pretty dangerous.
Attempting to charge a pack like shown has a very real risk of causing one or more of the cells to overcharge and breach, or worse, violently catch fire.
This... this is an hellish unbelievable nightmare, is asking for something to go wrong. It is certianly possible to invest the time & effort to balance the hell out of such a chaos-pack, but for one's own sanity, using normalized cells will save a lot of sanity & rework, and drastically decrease risks of catastrophic f-up. Don't do like this person! Do build weird electric systems though, unlike OP's way too broadscale doomsaying fear-mongering.
He made a case that can hold a bunch of cells. Not a battery pack.
When you put a lot of energy in a small space and release at all at once, it's called a bomb. Li ion batteries are small bombs that can be used to power electrical devices.
Some chemistries are safer than others, like A123 cells. The market did not care about safety and they went bankrupt. Energy density is king.
I can easily buy a 16 ton (1 ton = 12000 BTU/h) air conditioner, it uses a great deal more than 1kWh in 30 minutes.
http://www.ebay.com/itm/Carrier-16TON-R-410A-Puron-Air-Condi...
My point of reference I use to imagine energy is a major league baseball player hits a baseball with 1,234 J.
1KW/h is 3,600,000 J.
You did not account for the terminal velocity of the suitcase. It cannot accelerate indefinitely because of the air resistance.
If I assume that the suitcase will not break the sonic barrier (which seems reasonable), I get an upper bound on its kinetic energy of
0.5 * 60 pounds * (1 mach)^2 = 0.41528548 kilowatt hours
http://www.brandforsk.se/MediaBinaryLoader.axd?MediaArchive_...
The relevant datapoint is on page 61:
"As seen the yields of HF is much lower for the lap top cells, in fact the HF detected online was below the determined detection limit."
The graphs on page 101 also show HF concentrations below 4ppm --- and keep in mind this is basically all of the gases collected from the burning pack. Looking at the safety data for HF, the permissible exposure limit is only slightly lower at 3ppm and it's immediately dangerous at 30ppm.
In other words, it would be a bad idea to deliberately concentrate and inhale the fumes of a burning cell, but the HF probably isn't going to kill you. Some good ventilation of the area should be sufficient.
If that's happening due to a short (which can and does happen when a cell is charged improperly, or even put under resistive load after the cell is discharged below a safe limit -- copper or other ions, depending again on battery chemistry, can literally bridge across the electrolyte to short the cathode and anode) the result of the release of pressure combined with the reactive nature of now exposed lithium is a small rocket that shoots a plume of gasses like sulfur dioxide or hydrofluoric acid. Again, this depends largely on battery chemistry, and without an MSDS on these particular cells, there's no way to know. But there's a reason why any chemist you care to phone up will say, if you tell them you're in possession of a cylinder of a compressed compound that contains fluorine (it won't matter what kind, fluorine really really likes to bond promiscuously and with reckless abandon), they'll tell you that you're braver they are. Tell them you're intend to string up a few hundred of them and pass an electric current into them, and they'll call a hazmat team for you.
A casual stroll through forums frequented by flashlight fans (yeah, it's a thing) and you'll see plenty of demonstrations of what happens when a Li-ion cell begins a thermal runaway. And plenty of memorials to those who gave up their passion because they're on ventilators after experiencing profound damage to their lung tissues. Hell, ask the firefighters that respond to a fire at a battery recycling plant; granted, that's a bigger scale than one cell, but even one cell in a small room can, depending on its chemistry and how violently it's outgassing, emit enough HF to cause lung damage.
Read an MSDS yourself: http://www.uscg.mil/hq/cg4/cg432/docs/msds/MSDS_LiIon.pdf
LiPo "pouches" mentioned elsewhere in this thread are much less likely to explode spectacularly before bursting, and much less likely to exhaust a plume of corrosive, toxic chemicals in their wake.
Unlike what you seem to be implying, lion cells are NOT "under pressure" in normal use. They are at atmospheric pressure. The vent is specifically so in case of abnormal conditions, it allows any pressure to escape instead of causing the cell to explode.
result of the release of pressure combined with the reactive nature of now exposed lithium
In a lion cell, there is no "exposed lithium" in the metallic, highly-reactive sense. It's a solution of lithium ions in an electrolyte, whose only real hazard is its flammability.
I believe I know the flashlight forums you refer to, and the incidents of HF poisoning too. Those were lithium primary cells, which actually contain significant quantities of metallic lithium and are definitely more reactive than lion. Even the MSDS you refer to says "in spite of their name, these batteries do not contain any lithium metal".
The MSDS is also the easiest way to scare yourself into thinking everything is highly dangerous. For example, look at the ones for sodium chloride. By the way, I would not trust that one so much as it gives a boiling point for ethyl acetate, a liquid at room temperature, of -84C. Similarly, dimethyl carbonate is listed as boiling at +4C, when that's its melting point. Perhaps that's where your impression that the cells are normally under pressure came from?
Likewise, I recommend looking at the data on the electrolyte solvents:
https://en.wikipedia.org/wiki/Ethyl_acetate
https://en.wikipedia.org/wiki/Diethyl_carbonate
https://en.wikipedia.org/wiki/Dimethyl_carbonate
Not totally harmless, but not insanely toxic either.
I was interested to read about flashlight enthusiasts on ventilators, but all I could come up with was this:
http://www.candlepowerforums.com/vb/showthread.php?141137-In...!
And, more alarmingly, the part you omitted or glossed over: their plausible explanation for the lower HF detection (which, again, would depend wholly on the chemistry of the cells):
> the laptop cells exploded with liquid splashed on the walls in the equipment
Whoops.
Don't mess with these things unless you know how they can be safely tested, safely charged, and safely monitored. Li-ion protection failures (of various modes) were responsible for the Boeing Dreamliner fleet being grounded, Tesla refitting their battery packs (road debris caused a fire when it pierced a Li-ion cell), hoverboards being recalled, millions of dell laptops recalled after battery fires, and more recently, the Samsung Galaxy Note 7.
So, yeah. Safely tested, charged and operated is the key, and I wouldn't want to take that responsibility for a pack with as many batteries (and who knows which ones have their own standalone protection circuit in the cap) as in TFA.
> the laptop cells exploded with liquid splashed on the walls in the equipment
The less electrolyte that gets burnt, the less HF generated, which I hope you agree is a good thing.
and more recently, the Samsung Galaxy Note 7.
How many actually burned? It's a very tiny fraction. Manufacturers recall precisely to avoid the sort of hysteria that statements like yours generate, and it's not any indication of impending doom. The aviation industry is particularly risk-averse, so it's not surprising. But I don't think the risk is very high compared to a lot of other things in our lives, especially when you consider all the lion cells out there of questionable quality in use and yet behaving themselves. China has taken the lead in making 18650s and other lion cells almost as easily available as alkalines, but reports of fires do not appear to have increased anywhere near in a direct proportion to that. (Reports of cells failing to meet capacity specs, on the other hand...)
By all means handle with care (as you should with any energy source), but lion cells are not lethal weapons that will instantly kill you at the slightest provocation.
Regarding the battery exploding. Yeah, I'd agree that ... no! No, I don't agree at all! First, it exploded, so there's that. A cell in the middle of a multi-cell pack has nowhere to go. Second, it invalidated the experiment; they don't know how much HF would've been released in a real world scenario where the compressed cylinder of reactive metals and gasses is not free to "rapidly disassemble" into the air.
Now, moving on to Samsung's recall. How many failed? Sure, a small fraction. Do you know if yours will fail? How could you possibly know? Wait, I had something for this... oh, yeah. Safely test each cell.
Samsung didn't have that capability, their battery vendor didn't have enough engineers for all those house calls. You don't have that capability (you seem quite cavalier about the whole endeavor, so I'm guessing there). So, yes, since they can't know without testing, they recalled them all. What do you suppose they'll do then?
Probably, get together with the vendor, and test them.
Please stop suggesting to other readers that these things are perfectly safe when you know they're not. They're not tiny little bombs waiting to go off if you sneeze near one, but anyone using untested lithium-ion cells/batteries in untested configurations without a controller on each cell should be discouraged. We don't need a new category of Darwin award winners.
It's interesting to realize thought that we programmers are code producing machines that run on roughly 2kWh per day. If we produce 100 lines of code in a day, that's 20Wh per LOC. Not bad, actually.
A fantastic book. A Caltech trained physicist at Cambridge does the calculations to see if the UK could get all its energy needs sustainably.
Simple, easy to understand, and enlightening. It deserves the praise they talk about.
And it's free to download.
(handwaving away a method for 100% efficient conversion of mass to energy... But solving that would be a _really_ good thing...)
Yeah let's not use thermite to heat our houses people.
deliver 4-5 kWh of low-grade heat (or cold) into your home (depending on COP of a heat pump)"
Huh? I assume he means 0.4 - 0.5 kWh?
The "exchange rate" depends on the temperature; the maximum ("Carnot") heat pump efficiency is T_high/(T_high - T_low), where T_high is the temperature of the room being heated and T_low is the surrounding environment the heat is being pumped from (all on the absolute scale).
When T_high = T_low, the max COP is infinity, which has the physical meaning that "You don't need to spend any energy to keep a room the same temperature as its environment; that happens automatically."
https://en.wikipedia.org/wiki/Coefficient_of_performance#Der...
A heat pump just transfers heat from one location to another. The total thermal energy of the world is the same.
MacKay himself, a CalTech-trained physicist, worked at Cambridge. He died about five months ago, noted only modestly at HN: https://news.ycombinator.com/item?id=11500614
http://itila.blogspot.com/2016/04/index-for-first-23-cancer-...
Of the book, I find a few things particularly illuminating. For starters, it is rather UK-centric, though the concepts are of course generally applicable. Beyond that:
1. It goes through the major uses of energy in modern life. Getting a feel for the comparative magnitudes is quite useful.
2. It compares the various options for renewable energy. It turns out that there's a lot less energy in renewables than would be convenient. Wind and Solar are much of the easy stuff.
3. It mapps out both energy consumption and use by area. Realising how many watts per square meter are used and are available is useful.
4. He really presses the point that solving the energy conundrum requires large changes. Unplugging charging devices won't cut it. Hitting major consumption, especially transport, heating, lighting, and refrigeration, help a lot.
If you're interested in pursuing the issues further, I strongly recommend Vaclav Smil, whose books I've been going through. For a historical view, Smil's Energy in History, and the more recent two-volume book, Sources of Power, by Manfred Weissenbacher, explore how human history has been shaped by access to energy, from gatherer-hunter days, agriculture, coal, oil, and whatever comes next.
Fascinating and terrifying at the same time.
According to my car, it lets me drive 4.2 miles at highway speeds.
Are EPA miles not the same as normal miles?
There is a series of standardized driving profiles that is averaged to get a comparable, somewhat realistic value.
Better yet, you can fiddle with the dash controls and get a power meter: acceleration takes 30-60 kW, but regeneration can make up to 30kw.
Like the OP says, this kind of thinking really changes your perspective.
Reopening a plastic soda bottle.
From a web interactive I wrote: http://www.clarifyscience.info/part/ZoomB?v=A&p=CK6Ji&m=torq... (2014)
I do not know why (and I do not have a strong opinion on this), but somehow this (relatively recent) tradition of naming units after people feels weird to me. I know we are already used to these units, but imagine the unit of mass was called Einstein instead of kilogram.
It's a bit redundant to multiply power by time, when that's just an energy, but going between Watts and Joules is trivial (by design), so it's not too bad.
However, I can't think of a reason why hours would be easier to work with than seconds (as kiloseconds, if you want the same order of magnitude), especially regarding electricity?
I'm personally not a fan of the kWh, because it keeps being mistaken for kW, but I recognize that lack of need for a conversion factor help a lot of people make sense of energy.
1kWh = 3.6 MJ
Might as well just say 1 billion joules per second aka 1 GW then tack on or remove an hour if needed.
1 kWh = 1 joule hour per second
How does it make sense to have 2 different units of time in there?
This way it's easier to calculate how much energy your appliances uses. For example, if your vacuum cleaner is 1000W (1kW), running it for an hour will use 1kWh of energy which cost you can clearly see on your electricity bill. Unless you also want to re-lable all appliances, electric engines etc. in joules.. Sure, joule makes much more sense in physical calculations.
BTW, it's not 10 kW/h, but 10 kWh in a litre of petrol.
I think that's pretty accessible and could only add to the article's value by answering the question, "What does 'kilowatt-hour' mean?"
PV: Photovoltaic.
EV: Electric Vehicle.
TMDA: Too Many Damn Acronyms (It's a joke I heard at a company that had acronyms for everything).
"In a bar, somewhere.."
DETLA is also a FLA.
Furthermore, Are RFCs TLA? It appears that IANA, an FLA itself, standardized the use of TLAs in an RFC.
It really puts things in perspective when I look at a 1KW space heater. That's a lot of power!
What a great idea I think although I wonder if it's a pain, cutting through that hard, protective plastic that these cells are in for laptop batteries. Unless you buy just the cells themselves.
If you don't use a reverse cycle system you can more like 8 kwh of heat or cold
https://www.youtube.com/user/jehugarcia
he methodically tests old 18650 laptop cells, sorts them, builds battery packs and so on. He's converted a classic VW bus to electric power using his home-made battery packs and packs salvaged from wrecked teslas.
Wait what? where is this supply at
BTW: I haven't even connected these cells together yet - even that is not as simple as it may look like.
If you did it in addition to (as opposed to instead of) your exercise then the energy in the food you ate is massively greater than what you can get from the bicycle. If you eat more as a result then you wasted your money.
There are other concepts which are more bike-like: http://webseriesnetwork.com/photo/pedal-power-washing-machin...
Turns out you can generate a fair bit of energy from pedals!