Ping Jim Wilkins: Audio filter

Me too. And the others are somewhat better, given that they've been improved over the 30 years.

When I invent something that's a failure, I think about how many times in the past such a failure has been invented and forgotten. Only to be invented again because the previous failures are unknown.

Along that line, I found this article about John Goodenough, co-inventor of the lithium-ion battery, to be encouraging. John just invented another new battery, which he says will knock the li-ion battery dead. He's 94 years o ld and his comments about invention and age are interesting:

-a-94-year-old.html?_r=0

I'm crappy at product marketing, sales, and financing, but good at "techie" stuff like making this gizmo for cheap in an attractive housing.

So if you want to do the half that's hard for me, give me a call and I'll do the easy part.

Should be able to do the signal processing digitally, so the hard part will be making a user interface that allows the pro users to get the most out of it while making it easy enough for the ordinary guy so it doesn't just get thrown through the wall.

Along that line, I found this article about John Goodenough, co-inventor of the lithium-ion battery, to be encouraging. John just invented another new battery, which he says will knock the li-ion battery dead. He's 94 years old and his comments about invention and age are interesting:

That's a tempting thought, but look at it from a marketing perspective: This is a low-tech, analog device, and as Jim and Clare showed, there are slick, digital solutions on the market that even turn a cell phone into an audio spectrum analyzer.

I happen to like these simpler solutions, but I don't think a lot of people would go for it. The market would be really small. So I don't think it's viable except as a hobby thing that one might do for his own use and satisfaction.

I think we should pass on this one.

I can't claim that I'm good at it but I have a lot of experience designing user interfaces and writing the instruction manuals.

I'm experimenting with a homebrew grid / solar powered battery charger that can be set to run unattended or used manually to diagnose and restore neglected Lithium, NiCad and Lead-acid batteries. Earlier this week it recovered solder-tabbed Li-ion 18650s from "dead" cell phone boosters, this morning it brought back a fully discharged DeWalt NiCad pack enough for the automatic charger to accept it, and now it's working on an AGM that went bad in storage. The once useless battery delivers 60A.

It's a simple circuit, the hard part is knowing how to use it, and I don't have all the answers yet.

Maybe the reason they aren't on the market already is that they can as easily destroy a battery as save it.

-jsw

Speaking of Li-ion, Metabo claims that their new 36 V cordless tool battery pack can deliver 2,500 Watts, as used in their new 9-in. angle-head grinder.

Maybe my arithmetic is off, but that says roughly 70 A to me. The battery pack looks like it's just a standard 10-cell pack. I've read that the low-end internal resistance for advanced Li-ion cells is around 0.5 Ohms.

My calculation says the battery pack is dissipating 350 Watts or so at full load, which sounds unreasonable. This is a normal-size 36 V battery pack.

What do you think?

Aha, I think I answered my own question. It appears that internal resistance of Li-ion cells vary a lot by type, and the cells used in power tools can be as low as 18 milliohms.

That gives a more reasonable result.

Science Friday ran a small segment on new battery tech awhile back:

I don't remember them mentioning John but they covered several things being researched...

The following was thought to be close to production:

=== The most promising battery the documentary team came across is being developed by Tufts University Professor Mike Zimmerman, Pogue says. He?s confronted the problem of lithium-ion?s explosive liqu ids head on ? by eliminating the liquids.

"He's made a solid sheet of a special plastic, a special polymer, that lets the ions travel back and forth between the electrodes even better than a liquid electrolyte does," Pogue says. "And yet, because it?s a physical barrier, you can?t short out like lithium-ion batteries ca n. So these are plastic electrode batteries..." ===

Interesting stuff :)

quids head on

Yeah, I'll say it's interesting. The Braga/Goodenough battery uses a glass electrolyte and sodium, as an alternative to lithium:

Let's hope one or more of them pan out.

The little DC Volt/Amp/Watt meters sold to RC hobbyists for their Lithium packs read over 100A. The cheap tabbed 18650s I'm salvaging from cell phone portable chargers measure around 75 milliOhms full,

-jsw

Still, it's amazing that those smallish 6.2 Ah Metabo packs will deliver almost 70 A. That seems extremely high, but I guess that's where the technology is now.

That's a bit over 11C, which is well within the limits that model airplane battery packs are run these days. Every day packs come out that can handle more current for the capacity -- it's probably tools like that which are driving it.

Ooh -- maybe the answer is a smartphone app and a companion microphone -- and let people who want to scratch up their own microphone go ahead and do so.

Hmm. Hmm and hmm. I wonder if it's already done?

This claims 1000A:

I'm not going to risk testing my Whistler jumpstarter on the HF carbon pile just to report how much current destroyed it.

-jsw

How about the pocket sized (well, big pockets) lithium booster packs that will provide 600 amps of cranking power??

That, too, is pretty amazing. But cranking for a few seconds isn't going to generate the quantity of heat you get from running a grinder for a few minutes.

All in all, it's pretty staggering performance, both ways.

Long screwdrivers seem to get used more often than my stethoscope.