Today's Message Index:
----------------------
1. 05:56 AM - Elucidating write up on AVWeb (Christopher Cee Stone)
2. 06:53 AM - Re: who wudda thunk it? (Christopher Cee Stone)
3. 08:24 AM - 18650 cells (Christopher Cee Stone)
4. 09:12 AM - Re: evolution of lithium technologies (Charlie England)
Message 1
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| Subject: | Elucidating write up on AVWeb |
Enjoyed reading of Art's BD-4 project in the AVWeb article recently. It's
great to know more of the person behind the posts here. Kudo's Art...
sounds like a great airplane!
.chris
RV-8
Do Not Archive
Message 2
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| Subject: | Re: who wudda thunk it? |
A couple of data points... re. heat shrink tubing
I have harnesses that are 40+ years old. I built them for similar duty,
auto audio systems. They served well but were removed for upgrades. IIRC
they were in service for around 20 years. (yes I keep vehicles typically
for 300k miles). Again IIRC the heatshrink is Raychem showing no signs of
releasing or expanding.
My employer builds their own wire harness' albeit for fairly
benign environs. I have observed them after 30 years in service without
any loss of "shrink". They cover line voltage (120/240vac) connections.
The products are UL certified so if there were failures of the heat shrink
that caused a failure it would likely be reported. Again Raychem heat
shrink, clear as it is a medical equipment application.
...chris
On Sun, Sep 20, 2020 at 11:01 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
>
> I'm replacing an in-dash radio in the family chariot . . .
> seems the venerable ol' Kenwood CD player radio just
> doesn't cut it any more. Nobody carries CDs in the
> car and everyone wants to link their mobile phone
> to the radio via blue tooth. Ahhh fair Kenwood, tho
> has served me well . . . RIP.
>
> The vehicle to radio adapter harness needs to
> transition from Kenwood to JVC. Its a harness
> I built about 6 years ago. I was surprised to
> find that about some of the shrink over splices
> between radio and vehicle connectors had MIGRATED to
> locations that no longer cover the solder joint.
>
> I know that the shrink had a good grip on the
> irregularities of the solder joint when the harness
> was built. But after years of temperature cycles
> under the dash, the heat shrink kinda un-shrunk!
> It became more round and released it's grip on
> the joint. This allowed the tubing to vibrate
> clear of the solder joint! Only a few actually
> moved but all were loose and could be easily
> moved.
>
> We now know a lot more than we understand. Funky
> brand of HS? Normal behavior for a polyolfin
> shrink? I'm getting ready to mod the harness
> with a new radio connector . . . I think I'll
> use something different for joints. Perhaps
> crimp-shrink butt splices, solder sleeves or
> maybe double wall heat shrink with the internal
> adhesive. So many choices but no doubt all
> of them better than the choice I made last
> time.
>
> Just a heads-up guys.
>
>
> Bob . . .
Message 3
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Regarding 18650 cells... etc.
Bob's relayed test method would identify unqualified 18650 cells...
I purchased a few samples from different suppliers with ratings up to 4500
mAh. The ones rated at 4500 mah felt lighter in weight than the similar
cells rated at 3000 mAh. A friend designs medical x-ray machines so I
asked if he would x-ray one of the light weight cells and one "normal"
cell. Unfortunately I don't have an image to share. A description will
suffice. The light weight cell housed a much smaller cell. Hmmm!
Simerly I was replacing the output transistor in a regulated bench power
supply. I recall it was a 2N3055. I found a "deal" on Ebay. Five for
$5... Upon receipt I noticed the marking on the case didn't appear quite
right. It was labeled STM... lightly scratching the marking it readily
came off. Hmmm. Using a Dremel tool with a cut-off wheel I removed the
top of the case. Voila! A tiny junction with .002" bond wires! That
someone can make a living going to the trouble of
counterfeiting transistors!
Caveat Emptor
Chris Stone
Message 4
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| Subject: | Re: evolution of lithium technologies |
On Sun, Sep 20, 2020 at 11:56 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
>
> I've been studying current options for lithium
> cells on the market. Discovered some interesting
> things. For example . . . this excerpt from the
> engineering data sheet on an 18650 cell cited
> as suitable for battery powered tools:
>
> [snippped]
> What insults might these cells endure if
> incorporated into a flight system? Any worse
> than those cited above? Just thinking . . .
>
>
> Bob . . .
>
That got me thinking (and searching).
A wade into the shallow end of the data pool yields only damp feet when it
comes to actual *power* capacity. The highest 'continuous current' rating I
could find on 18650 cells is around 30A. That would imply, at 1st glance,
at least 10 parallel cells per link in the serial chain. Many were limited
to around 2A continuous. I couldn't find any specs on peak current, either
on the bigger vendor sites, or on actual mfgr data sheet pdfs. Descriptions
of, and differences among, the various chemistries and naming conventions,
are all over the map, depending on which interweb 'authority' you choose to
accept. Obviously more going on than I can see in the normal data sheets,
since there are dozens of functional examples of starting batteries on the
market.
I'd certainly be game for rolling my own battery, but picking the right
cell seems a task not suited to mere mortals.
Charlie
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