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What does a kilowatt hour look like?

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Re: What does a kilowatt hour look like?

#131

Post by Jugurtha »

vacri wrote: post #62
Jugurtha wrote: post #25

Earlier quoted context omitted.

COP: Coefficient of Performance. PV: Photovoltaic. EV: Electric Vehicle. TMDA: Too Many Damn Acronyms (It's a joke I heard at a company that had acronyms for everything).

Well, a TLA is a TLA, but an FLA is not an FLA (it is also a TLA)...

It depends. Facing each other, when one says "to the right", does he mean to his right or to the interlocutor's right?

Furthermore, Are RFCs TLA? It appears that IANA, an FLA itself, standardized the use of TLAs in an RFC.

https://tools.ietf.org/html/rfc5513

Re: What does a kilowatt hour look like?

#132

Post by rsync »

spdustin wrote: post #87
userbinator wrote: post #80

Earlier quoted context omitted.

I think your concerns are somewhat alarmist and tend to be a bit scaremongering. You may want to read an actual study about just how much HF is present in the fumes of burning cells. In this one, near the end they burned a whole laptop pack and analysed the gases that were emitted: http://www.brandforsk.se/MediaBinaryLoader.axd?MediaArchive_... The relevant datapoint is on page 61: "As seen the yields of HF is much l…

The PF6 ions in the electrolyte of some Li-ion batteries (not all use the same chemistry) will readily combine with hydrogen in the air to form HF if the battery is combusting. Cylindrical Li-ion cells, like those part of an 18650 battery, literally hold their chemistry under pressure, and a thermal runaway will normally cause the vents in the cell to release the pressure. If that's happening due to a short (which ca…

"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."

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...!

Re: What does a kilowatt hour look like?

#133

Post by [deleted] »

ralfd wrote: post #121
jrockway wrote: post #57

Earlier quoted context omitted.

You have to realize that 1kWh is a lot of energy. Imagine being hit (in a world without an atmosphere) by a 60 pound suitcase falling out of an airliner flying at 45,000 feet. Same amount of energy as that battery pack. (Alternatively: the most powerful air conditioner you can buy running full blast for 30 minutes. Incidentally, that battery pack has as much energy as 100mL of gasoline, which is why gasoline-powered…

Wow, 100 ml of gasoline could propel a suitcase into the stratosphere? That seems so counterintuitive.

[deleted]

Re: What does a kilowatt hour look like?

#134

Post by novaleaf »

jfoldager wrote: post #106
akiselev wrote: post #90

Earlier quoted context omitted.

In other words: 1 kWh is the equivalent of the average MLB player hitting a home run roughly every 1.2 seconds.

.... For one hour. Your units do not check out. He just needs to hit the ball ~ 3000 times. Imagine that exploding in your face.

love that visual the best ;)

Re: What does a kilowatt hour look like?

#135

Post by spdustin »

userbinator wrote: post #119
spdustin wrote: post #92

Earlier quoted context omitted.

I had to come back because the paper doesn't specify the chemistry of the laptop battery; you can't use this as evidence to support anything other than caution around Li-ion batteries and cells. 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 spl…

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 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 act…

Are you serious, or trolling? Weird question to ask outright, but I wanted to save time.

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.

Re: What does a kilowatt hour look like?

#136

Post by ge96 »

TD-Linux wrote: post #49
ge96 wrote: post #41

I like his battery haha, colorful. Also nuts to test all those cells. Make sure they're all roughly the same performance. wonder how hard it would be to find a bad cell.

Probably the most obvious indication would be temperature. Assuming they are in parallel, it'd be quite wise to measure their discharge curves to only select similar cells - that would also highlight any bad ones.

Hmm. It did appear that the cells were all oriented in the same direction.

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.

Re: What does a kilowatt hour look like?

#137

Post by StavrosK »

jrockway wrote: post #94
walrus01 wrote: post #72

Earlier quoted context omitted.

> (Alternatively: the most powerful air conditioner you can buy running full blast for 30 minutes. 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...

I mean to say, "plug in to your 120V 18A circuit".

I wonder why we have a tendency to nitpick rough estimates and go "YOU DIDN'T ACCOUNT FOR X EDGE CASE!", when even we get the gist.

Re: What does a kilowatt hour look like?

#138

Post by throwaway7767 »

Riding an electric bike has made me very aware of how much work can be performed with a given amount of power. Watt-hours aren't abstract anymore. 1kWh can get me and my stuff 120km easily if I pedal, probably closer to 80km if I used battery power only. Also instantaneous power, 200W is enough to move my bicycle, me and my stuff at a low cycling speed (15-20km/h) on the flat.

It really puts things in perspective when I look at a 1KW space heater. That's a lot of power!

Re: What does a kilowatt hour look like?

#139

Post by throwaway7767 »

gravypod wrote: post #130
qoobaa wrote: post #110

Earlier quoted context omitted.

I think @gravypod actually meant parallel connection, it might be quite dangerous in fact - you don't even need to draw anything from the battery to mess things up. If you connect a 100 cells in parallel and one cell dies creating a short in the circuit, the rest of cells will discharge through the shorted one. When you short a single 18650 cell, it outputs about 6-7 A of current on average. Multiplying by 100 gives…

Yes that was mentioned in one of the maaaany EEVBlog videos iv watch that these fail closed sometimes as well as the recommendation that "you should never buy lipo cells without a built-in controller" comeing from a guy far smarter then I about electronics design. If he is afraid of it, it's for a good reason.

> Yes that was mentioned in one of the maaaany EEVBlog videos iv watch that these fail closed sometimes as well as the recommendation that "you should never buy lipo cells without a built-in controller" comeing from a guy far smarter then I about electronics design. If he is afraid of it, it's for a good reason.

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.

Re: What does a kilowatt hour look like?

#140

Post by viewer5 »

StavrosK wrote: post #137
jrockway wrote: post #94

Earlier quoted context omitted.

I mean to say, "plug in to your 120V 18A circuit".

I wonder why we have a tendency to nitpick rough estimates and go "YOU DIDN'T ACCOUNT FOR X EDGE CASE!", when even we get the gist.

If I had to guess, it's someone who's like "I wonder how big that AC unit is" because the idea tickled their imagination, googles it, then finds that it doesn't quite match with the scenario given.
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