On Saturday, April 8, 2017 at 8:25:35 PM UTC-4, Clare wrote:
On Sat, 8 Apr 2017 14:00:31 -0700 (PDT), wrote:

On Saturday, April 8, 2017 at 4:48:35 PM UTC-4, Jim Wilkins wrote:
wrote in message
...
On Saturday, April 8, 2017 at 2:59:13 PM UTC-4,
wrote:
On Saturday, April 8, 2017 at 2:00:06 PM UTC-4, Jim Wilkins wrote:
"Tim Wescott" wrote in message
...
On Fri, 07 Apr 2017 08:51:21 -0700, edhuntress2 wrote:

Yo Jim -- and anyone else who may be interested.
.............

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.

--
Tim Wescott

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?

--
Ed Huntress

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.

--
Ed Huntress

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,
150 nearly discharged.
http://www.ebay.com/itm/like/3317138...&ul_noapp=true

-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.
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.

--
Ed Huntress