Not related, but I hate this unit. Can't we just talk about Joules?
Same here.
1 kWh = 1 joule hour per second
How does it make sense to have 2 different units of time in there?
What does a kilowatt hour look like?
91–100 of 147 posts
Re: What does a kilowatt hour look like?
#92Given how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. 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 c…
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…
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 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.
Re: What does a kilowatt hour look like?
#931 kWh = 3600 kJ
= 95g of lard (or body fat!)
= 85g (115 mL) of petrol/gasoline
= 1.5 Big Macs
= 40% of an average male's daily energy intake
= ...
Re: What does a kilowatt hour look like?
#94Earlier 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…
> (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".
Re: What does a kilowatt hour look like?
#95"So, what a kilowatt hour of high-grade electric energy can do for you? Many useful things, i.e.: 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?
A light bulb/resistor converts electricity into heat. So the total thermal energy of the world is greater.
A heat pump just transfers heat from one location to another. The total thermal energy of the world is the same.
Re: What does a kilowatt hour look like?
#96Given how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. 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 c…
For those wondering about how nasty HF is: http://blogs.sciencemag.org/pipeline/archives/2004/03/03/thi...
Re: What does a kilowatt hour look like?
#97Earlier quoted context omitted.
> Newton-meter 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.
How recent is the trend? Most of the units I know are named for people: Joule, Watt, Volt, Ampere, Newton, Angstrom, Ohm, ...
By convention, SI units named after people have capital letters for their symbol.
Re: What does a kilowatt hour look like?
#981/33.7 of an exceptionally privileged imperial gallon of petrol, according to US regulators.
Re: What does a kilowatt hour look like?
#99A single 12V 100Ah VRLA Deep-Cycle battery might be a better idea that's more familiar to a much larger chunk of the population, and you have the added bonus of having enough capacity to make up for the typical conversion/transmission losses in most scenarios, thus delivering a true kilowatt-hour!
Re: What does a kilowatt hour look like?
#100Given how popular (and damn near impossible to discern) unsafe and unprotected lithium-ion batteries are, the idea of making a homegrown power wall terrifies me in ways I can't even begin to contemplate. 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 c…
Building a pack from random cells like this is pretty much a cardinal sin with Li-Ion pack design. Cell resistance and state of health are carefully matched during pack manufacture to ensure cells charge and discharge evenly. Li-ion cells are pretty sensitive, so on top of that, large packs have battery management systems (BMS) to balance cell voltages and monitor for faults and damaged cells. Attempting to charge a…
Yeah, very much. Some basic dilligence with a somewhat even set of cells will probably be harmless. I would not be afraid of that kind of homebuilt power-store, if some decent practices are followed. (But you should do your dilligence & check to make sure all the cells remain ok, as you start using this pack!)
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.