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