Today's Message Index:
----------------------
1. 06:32 AM - Re: Re: Today's trivia dump . . . (Robert L. Nuckolls, III)
2. 08:26 AM - Re: Today's trivia dump . . . (Robert L. Nuckolls, III)
3. 09:14 AM - Re: Today's trivia dump . . . (ashleysc@broadstripe.net)
4. 02:09 PM - Re: Today's trivia dump . . . (Eric Page)
5. 05:11 PM - Re: Re: Today's trivia dump . . . (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Today's trivia dump . . . |
At 01:09 AM 4/7/2017, you wrote:
>
>Indeed; plus the dangers inherent in a mains-powered project.
>
>I hadn't yet seen the eBay item you linked. The Chinese
>manufacturers never cease to amaze with their ability to crank out
>high-dollar items at bargain basement prices.
>
>This got me thinking about a simple way to accomplish this with
>stuff we might have on hand at the bench or could get
>cheap-and-quick. With the idea that lead-acid batteries are
>ubiquitous, safe and able to provide ample current to weld the tiny
>spots needed to secure battery tabs, here's what I came up with:
>
>http://preview.tinyurl.com/knz5te2
This is almost exactly what I crafted to
replace the failed pulse controller on a friend's
spot welder some years ago. This was an AC welder
so I could use a photo coupled triac to control
primary supply current. The only questions that come
to mind immediately about the battery+contactor
configuration is the ability to control pulse current
as well . . . some high current resistors (i've used
coils of steel clothesline wire). Also, you may want
to craft your solenoid driver to withstand the inductive
kick inherent in the solenoid's windings. Adding
a diode causes a large contactor increase in drop-out-delay
which MIGHT affect your selection of optimum current
x time . . . or not.
But the thing is worth pursuing . . . we could do
an Eric's Shop Notes page on the website to assist
others in repeating a useful experiment.
Bob . . .
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Today's trivia dump . . . |
At 01:10 PM 4/6/2017, you wrote:
>Bob,
>
>Thanks for this update. I had been really
>wondering if those Energizer "Advanced Lithium"
>batteries were worth the extra cost. I just did
>a lookup on Amazon to find the current pricing
>for the AA cells ' seems to be around $1.27 each
>(cheapest I ccould find). By comparison, the
>Kirkland brand alkaline cells from CostCo run
>about $0.25 per cell. Even if the "Lithium"
>cells last 3 times longer, they still cost 5
>times as much! Looks like your old advice from
>2002 still rings true: "Buy cheap and change often!"
Agreed . . . but with this 'special case'.
As a primary cell standby battery, cost of
ownership has to include a significant
$time$ expense. It occurs to me that a
welded (or carefully soldered) array of
these more robust cells might well offer
an attractive option for keeping these
nifty little panel appliances running
in situations where our preventative
maintenance and/or less than artfully
conducted FMEA does trigger a black-panel-
syndrome.
'Standby' batteries have been an intuitively
seductive idea since the first panel mounted
electro-whizzy was installed on an airplane.
As we've discussed on the List many times
over the years, bad days in the cockpit are
rarely based on loss of electrical power . . .
and when they do include total electrical
failure, we have generally deduced root cause
to be something OTHER than deficient hardware.
System architecture and/or pilot ignorance
plays a major role in virtually every
dark-n-stormy night story published in the
popular aviation rags.
The alkaline AA cell is a demonstrably
robust and predictable source of energy.
In the very first edition of the 'Connection,
I suggested DIY arrays of alkaline D-cells
as a potential back-up source. In the 25+ years
since, energy requirements for some useful appliances
are so low that the lowly 9v transistor radio
battery becomes a EMF to consider . . . with
attractive cost, weight, volume and performance
ratios.
This exploration into a world of flight
forced into Plan-C operations SHOULD be more
academic than practical . . . but it sounds
like fun.
Bob . . .
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Today's trivia dump . . . |
Hi Bob;
Hi All;
This is good work that you do. Much preferable to trusting manufacturer's hype.
Cheers! Stu.
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Thursday, April 6, 2017 9:29:08 AM
Subject: AeroElectric-List: Today's trivia dump . . .
I think I've written about a project to repeat the
experiment I did on AA alkaline cells 14 years ago . . .
http://tinyurl.com/mhztc2b
I've been keeping a constellation of AA-cell products
in the super-duper-battery-runner-downer for several
weeks and at first blush at most of the data, the
original deductions about alkaline cell quality vs.
costs and advertising hype haven't changed.
There are a couple interesting things I've discovered
that I'll share with the List.
There's a line of alkaline cells purported to be
enhanced with lithium. A noteworthy example is
the Energizer 'Advanced Lithium' brand. These
are not lithium-ion cells . . . they still present
the expected 1.6 volt/cell open circuit potential
as their rudimentary cousins but unlike MOST 'enhanced
formulas' these do indeed offer improved performance in the
same envelope.
The energy traces below show a generic pair of alkaline
AA cells that have delivered ~1.4 Watt-Hrs of energy . . .
about the same numbers as the first experiment in 2002.
Then we have a trio of traces that have delivered 3.6
Watt-Hrs of energy or about 2.5 times that of the
non-lithium cell.
There are three additional traces of interest . . . they
too are generated by the discharge test of some advanced
lithium cells. The general shape of the curves are the
same as for the first three described above . . . but they
averaged a 15% lower value of delivered energy and the output
voltage is 'ragged' or unstable.
This is caused by tiny amounts of resistance introduced
by the connections to the test equipment that can arise when
the cells are connected with the spring-loaded holders
common to 99.999% of all cylindrical cell powered products.
These resistance values are small . . . and generally have
little effect on appliance performance for applications
with smaller current demands. The tests I'm conducting use
a 300 mA constant current discharge rate. At this rate . . .
and anything higher . . . there is a potential for battery
holder resistance to degrade system performance.
This fact is part of the foundation for why I explored
and ultimately recommended the 9v alkaline cells in a standby
battery application a few days ago. The very low current
demand in the application under discussion did not exclude
the 9V cell.
Obviously, the AA cell offers a larger energy bucket for
such tasks . . . but getting a firm electrical grip on
the cell's electrical energy is a bit more problematic.
My energy studies are being conducted with cells having
SOLDERED leads eliminating the holder issues . . .
indeed, one could build up disposable cell arrays using
similar techniques. But they need to be done with care
lest the cells be damaged by soldering heat.
It would be really cool to use tab-welders common the Ni-Mh
and Li-Ion arrays. The AA alkaline cell has a really small
(+) terminal . . . more difficult to weld on. I have some
alkaline D-cell arrays for video cameras that were welded . . .
but the AA-cell is more problematic.
I may do an article on the techniques I use for soldering
to AA-cell . . . it's not difficult.
It seems that the past few weeks discoveries in my AA-cell
testing offer another choice for DIY standby battery
construction. As soon as I've squashed all the energy
out of the current constellation of test articles, I'll
do some testing on the effects of soldered leads.
Watch this space . . .
Bob . . .
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Today's trivia dump . . . |
Good catch; there's not much point in having 50mS pulses if the relay takes 1/3
of that again to release. I've added a 200V Zener across the coil to allow its
stored energy to dissipate faster. I changed the MOSFET to an Infineon IPA65R650CEXKSA1
that's Vds=650V rated, and I've annotated a minimum Vds=500V for
substitution.
Updated schematic:
http://preview.tinyurl.com/knz5te2
WRT pulse current, I suppose you could use a power resistor or DIY facsimile -or-
get fancy with a beefy MOSFET gated by a pot-controlled op-amp sensing a shunt.
Based on the results shown in the various YouTube videos on this subject,
my gut says current control isn't really necessary for the limited purpose of
welding tabs onto cells. I think my first go at this would be to just control
heat with pulse width. More R would be easy to add if found necessary.
Let me know if I can put this together and send it to you to try. I don't have
a need for it at the moment and my ability to measure how it works is limited
(most of my equipment is in storage), but I do have the time to build it if you
can get some use from it or if you think it will add to our collective tool
box.
Is there anything else you would suggest changing?
Eric
Robert L. Nuckolls, III wrote:
> At 01:09 AM 4/7/2017, you wrote:
> This is almost exactly what I crafted to replace the failed pulse controller
on a friend's spot welder some years ago. This was an AC welder so I could use
a photo coupled triac to control primary supply current. The only questions that
come to mind immediately about the battery+contactor configuration is the
ability to control pulse current as well . . . some high current resistors (i've
used coils of steel clothesline wire). Also, you may want to craft your solenoid
driver to withstand the inductive kick inherent in the solenoid's windings.
Adding a diode causes a large contactor increase in drop-out-delay which MIGHT
affect your selection of optimum current x time . . . or not.
>
> But the thing is worth pursuing . . . we could do an Eric's Shop Notes page on
the website to assist others in repeating a useful experiment.
>
> Bob . . .
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=468133#468133
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Today's trivia dump . . . |
>WRT pulse current, I suppose you could use a power resistor or DIY
>facsimile -or- get fancy with a beefy MOSFET gated by a
>pot-controlled op-amp sensing a shunt. Based on the results shown
>in the various YouTube videos on this subject, my gut says current
>control isn't really necessary for the limited purpose of welding
>tabs onto cells. I think my first go at this would be to just
>control heat with pulse width. More R would be easy to add if found necessary.
Remember that total heat = K x T x I(SQUARED)
. . . while there will be some current limiting
offered by wiring and contactor resistance, the
'weld current' available from a healthy battery
can exceed many hundreds of amps.
I would sure build in some sort of limiting.
It occurs to me that incandescent lamps in
parallel might offer an interesting current
profile.
Inrush tapering over tens of milliseconds
will come asymptotic to the running current
about 100 mS later. So an array of 10, 55w lamps
(4A running) would settle out at 40a but deliver
a pretty good start up jolt . . .
Just a thought. In any case, an open coil of clothesline
wire can be a pretty rugged, adjustable limiter. Used
the stuff in a motor inrush controller for the a/c
compressor motor on King Airs wayyyyy back when . . .
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|