Forgot your password?

Comment: That said... (Score 4, Informative) 53

by Rei (#47437451) Attached to: Sand-Based Anode Triples Lithium-Ion Battery Performance

... the greater your capacity, the less cycle life matters. If you want an EV that battery that will run a 250Wh/mi vehicle for an average 20 miles a day for 15 years, then you want it to cycle through about 30MWh. If you use a 100 mile (25kWh) battery pack, then that's 1100 cycles. If you use a 200 mile (50kWh) battery pack, then that's 550 cycles. If you use a 400 mile (100kWh) battery pack, then that's a mere 275 cycles. Actually, the improvement is even better than that in the real world, because the greater your capacity vs. how far you're actually driving, the more you can cycle the cells through a less destructive state of charge range rather than doing deep discharges.

A lot of people picture battery packs in EVs backwards, they think that things like hybrids stress the packs the least, PHEVs moderately, and EVs the worst. But it's reversed. If you look at how big hybrid packs are vs. how much electric range they hold, you'll see that they're disproportionately large, even after you factor in any differences in Wh/kg. The reason is that because hybrid packs get cycled so much, they have to keep the cycling in a very narrow state of charge range, only allowing shallow discharges. So if you only have a narrow discharge range, you have to make your pack bigger to make up for it. EVs can discharge through much more of their pack because they need fewer total cycles and only rarely go down toward the lower end of their allowable discharge range. Some EVs also let you limit the max that your pack charges up to to further extend lifespan (it's usually destructive both to use the very top end and the bottom end of the discharge range).

Comment: Re:Correct me if I'm wrong, but... (Score 4, Informative) 53

by Rei (#47437401) Attached to: Sand-Based Anode Triples Lithium-Ion Battery Performance

1024 mAhg1 is excellent capacity even vs. brand new graphite or amorphous carbon, about 3x as much as graphite's maximum. Silicon's theoretical max is 8-10x that of graphite, but the main problem with it is durability, it tends to tear itself apart on loading. There are silicon anodes in some newer li-ion cells on the market, but the tech is in its infancy.

That said, the real papers you want to be on the lookout for are cathode improvements, there's a lot more potential for volume/mass reduction there than in the anode. But it seems to be a more difficult challenge. Getting a 3x improvement in anode density is absolutely not the same a getting a 3x improvement in battery life.

Comment: Re:Little Bit of History Repeating. (Score 5, Insightful) 53

by Rei (#47437377) Attached to: Sand-Based Anode Triples Lithium-Ion Battery Performance

Commercial li-ion battery energy densities have continued to improve during that time period, including the commercial introduction of cells with silicon anodes. Of course, silicon anodes are a new tech, so there's a great deal of room for improvement, which probably won't come close to "maxing out" for a decade or more.

Of course, that said, this article is your typical fluff piece following the guidelines of fluff science reporting.

1. Present an oversimplified version of one technology challenge that may or may not address the biggest issue and certainly doesn't address all of them - but don't mention that.
2. Introduce an outside-the-establishment loner with a passion - or at least someone you can try to present as "outside the establishment" and glaze over anyone who helped him.
3. Loner gets a "vision" based on some everyday activity
4. Present their solution and make it out to be a huge revolution that will certainly solve all our problems - if they can only get corporate backing / funding!

I think these sort of articles hurt the image of science because people read them, think "OMG, all our problems are solved!", then when everything's not solved afterward, fail to trust science in the future. For example, in this case, the most important element to improve is the cathode, not the anode. And cathode improvements are less common and usually less major than anode improvements. There's also tons of different anode improvements out there in various stages of research. Pretty much all of the silicon ones get way better than graphite or amorphous carbon.

That doesn't mean that this isnt an important paper - actually, from looking at it, it looks pretty good. It's just not "all that".

BTW, anyone know how credible this journal is? I see it's hosted on but not part of Nature, and I tried to find an impact rating for it but couldn't.

Comment: Idiots ruin safety records (Score 1, Insightful) 404

by jandrese (#47434205) Attached to: The First Person Ever To Die In a Tesla Is a Guy Who Stole One
I think the real message here is that Tesla's stellar safety record is due at least in part to its exclusivity and high price tag. The kind of people who can afford it are generally safer drivers. It's not a used Dodge Charger that some 16 year old asshole with a shiny new drivers license and Dad's credit card can buy off of the lot for a few thousand bucks.

Comment: What about the ads (Score 5, Interesting) 138

As I understand it, if they get classified as a cable company Aero will be legally allowed to put their own ads into the stream, overwriting the ads the original broadcaster put in there or maybe removing them entirely if they still want to be an entirely subscription driven service. They could really seriously piss off some OTA broadcasters with this approach.

Comment: Re:CFL's lasting almost 30 years (Score 1) 223

by jandrese (#47427121) Attached to: My most recent energy-saving bulbs last ...
You could get a CFL in 1985? Back then "Compact" florescent seemed to be those fixture with the 12" diameter circular tube and a conventional ballast. They certainly did not fit in a traditional socket. I started seeing what we consider CFLs around 2000 or so, and the first versions were pretty bad. There was some seriously defective Chinese garbage all over the market during the first few years. Once I found a bulb I liked (Commercial Electric from Home Depot--they don't appear to exist anymore sadly), I bought a bunch and swapped out most of the bulbs in my house.

Comment: Re:2-year CFLs (Score 1) 223

by jandrese (#47427089) Attached to: My most recent energy-saving bulbs last ...
It's strange. Of the many CFLs I've installed, I've only had three failures. Two of which were early Walmart bulbs that were shit. The other was one of the bulbs I settled on for everything else, it got a smoky smell and discolored the plastic near one end of the tube: clearly some magic blue smoke escaped. Other than that, I've had 10 years of reliable service from a couple dozen bulbs. A few of the oldest ones (4 bulbs) have a "warm up" time where they are noticeably dim when you turn them on at first, but all of the other bulbs come on at or near their full brightness.

I do have underground power though, I wonder if comes out cleaner thanks to that?

Comment: Re:Kids mix fine with LED's (Score 1) 223

by jandrese (#47427039) Attached to: My most recent energy-saving bulbs last ...
My plan is to switch out my CFLs for LEDs when the CFLs burn out, but thus far none of them have. I did the bulk of the CFL replacements back in 2004 and they just don't want to quit. The only LED light I've been able to install is to replace an incandescent flood on a circuit controlled by a dimmer switch.

Dreams are free, but you get soaked on the connect time.