High-capacity NiMH cells -- very rapid self-discharge common?

On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington"
wrote:


"John Turco" wrote in message
...
Neil Harrington wrote:

"John Turco" wrote in message

edited for brevity

I was most intrigued by rubber-powered, stick-and-tissue airplanes,
during
my model-building days, long ago.

edited

I remember the rubber-powered stick and tissue models with great
affection,
though I was never very good at building them. I'd be tempted to get back
into rubber-powered free flight now myself, if I didn't already have too
many hobbies and too little sense of organization and discipline.

Hello, Neil:

My first such kit was a Guillow's Hawker "Hurricane," which I purchased
at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69 cents,
in 1966!

(Hey, that was a lot of money, for a 12-year-old kid, back then. g)

I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits
in the '40s. Comet kits were usually 10 cents as I recall, and that even
included a tiny glass tube of model airplane cement. Not enough cement to
actually put the plane together, unless perhaps you were very skillful at
economizing on it. Those 10-cent kits were of course the smallest of the
several sizes. Wing ribs and fuselage formers, etc., were all printed on a
thin sheet of balsa and had to be cut out my hand -- very hard to do with an
ordinary razor blade.

The first time I attempted to make a kit I glued several sections
together using a page of newspaper to protect the table. When I tried
to remove the glued sections, great chunks of newspaper came up with
the section.

I bought a number of kits but never succeeded in finishing one until finally
I completed a (somewhat larger) Fokker D.VII when I was about 16. That flew
reasonably well but I got tired of doing all that hand-winding of the rubber
motor for a very short flight. It wasn't until much later that I learned
about more serious modelers using a geared hand-powered drill to wind the
motors. That would have saved me a lot of aggravation.

I remember hand-winding until the last few turns, and accidently
letting go of the prop. Finger-buster.

Mostly as a kid I experimented with hand-launched gliders, made entirely of
balsa sheet and not requiring any of that tricky building. I didn't return
to stick and tissue models until the '60s or so, and then only briefly.

I had a brief experience launching balsa sheet gliders from my
grandparents' second story porch. I'd glue a thick string of yarn to
the body, soak it with lighter fluid, light the plane, and send it off
to spiral down like the fighter planes in the RKO newsreels. Great
fun...until one landed on a neighbor's automobile's convertible top.
Luckily, it only scorched the top, and I was never caught. Never
tried it again, though,

--
Tony Cooper - Orlando, Florida

"tony cooper" wrote in message
...
On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington"
wrote:


"John Turco" wrote in message
...
Neil Harrington wrote:

"John Turco" wrote in message

edited for brevity

I was most intrigued by rubber-powered, stick-and-tissue airplanes,
during
my model-building days, long ago.

edited

I remember the rubber-powered stick and tissue models with great
affection,
though I was never very good at building them. I'd be tempted to get
back
into rubber-powered free flight now myself, if I didn't already have
too
many hobbies and too little sense of organization and discipline.

Hello, Neil:

My first such kit was a Guillow's Hawker "Hurricane," which I purchased
at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69
cents,
in 1966!

(Hey, that was a lot of money, for a 12-year-old kid, back then. g)

I remember the Guillow's kits, also Cleveland kits and plans, and Comet
kits
in the '40s. Comet kits were usually 10 cents as I recall, and that even
included a tiny glass tube of model airplane cement. Not enough cement to
actually put the plane together, unless perhaps you were very skillful at
economizing on it. Those 10-cent kits were of course the smallest of the
several sizes. Wing ribs and fuselage formers, etc., were all printed on a
thin sheet of balsa and had to be cut out my hand -- very hard to do with
an
ordinary razor blade.

The first time I attempted to make a kit I glued several sections
together using a page of newspaper to protect the table. When I tried
to remove the glued sections, great chunks of newspaper came up with
the section.

That sure sounds familiar! . . . I wouldn't be surprised if every kid did
that the first time or so.


I bought a number of kits but never succeeded in finishing one until
finally
I completed a (somewhat larger) Fokker D.VII when I was about 16. That
flew
reasonably well but I got tired of doing all that hand-winding of the
rubber
motor for a very short flight. It wasn't until much later that I learned
about more serious modelers using a geared hand-powered drill to wind the
motors. That would have saved me a lot of aggravation.

I remember hand-winding until the last few turns, and accidently
letting go of the prop. Finger-buster.

My main worry was getting in a turn too many, busting the rubber band with
resulting damage to the fragile fuselage. That never actually happened but I
always worried about it.


Mostly as a kid I experimented with hand-launched gliders, made entirely
of
balsa sheet and not requiring any of that tricky building. I didn't return
to stick and tissue models until the '60s or so, and then only briefly.

I had a brief experience launching balsa sheet gliders from my
grandparents' second story porch. I'd glue a thick string of yarn to
the body, soak it with lighter fluid, light the plane, and send it off
to spiral down like the fighter planes in the RKO newsreels. Great
fun...until one landed on a neighbor's automobile's convertible top.
Luckily, it only scorched the top, and I was never caught. Never
tried it again, though,

:-)

Does sound like fun.

Neil

In article ,
"Neil Harrington" wrote:

I recently bought some cheap no-name (actually "Tenergy," whatever that is)
2600mAh AA cells on eBay. I haven't tried to assess the accuracy of their
rating, don't know how I'd do that anyway, but I'm flabbergasted by how fast
they self-discharge -- a couple days or so, sometimes almost overnight, it
seems. Tried leaving them on charge overnight, no difference. Tried
"conditioning" them in a Maha C204W, still no difference. Charged with a
Maha C401FS, individual charging circuits for each cell, still no
difference. So far they do not seem to improve with use either.

So I tried some more cheap no-name (really no-name this time, just cell info
on a pale green case) 2600mAh cells from a different eBay source. Pretty
much the same thing. From fully charged they go flat amazingly fast with no
use at all. Not actually zero-voltage flat, they'll still light a two-cell
flashlight, but flat enough that a couple of days after charging they won't
operate an old four-cell Minolta S404 for more than a few shots.

I've used no-name (or unheard-of name) NiMH cells from eBay sellers before,
with excellent and reliable results, and most of those cells are still
giving me good results after several years. But they were of lower capacity,
2000 mAh or less. So I'm wondering if fast self-discharge is a
characteristic of these newer 2600mAh NiMH cells in general, or if it's just
that cheap cells ain't what they used to be.

Neil

Some NiMH cells will discharge extremely rapidly when they're hot. I
have seen NiHM cells left in a hot car go dead in one day. Generally
they're not so bad at normal room temperatures. A faster discharge rate
probably indicates poor quality.

Throw the 300mA Maha charger in the trash. Fast chargers must produce
between 0.3 and 1 times the Ah rate in charging current for the battery
to show signs of nearing a complete charge. Your new set of batteries
require a charge current between 780 mA and 2600 mA. Below that
current, all detectable parameters of the battery are more influenced by
external factors than by the charge level. A slight breeze or a passing
ray of sunlight can cause the 300mA Maha chargers to terminate charging
early or never at all.

Some good general NiMH data is he
http://data.energizer.com/PDFs/nicke...ide_appman.pdf

--
I will not see your reply if you use Google.

Neil Harrington wrote:

"John Turco" wrote in message

edited for brevity

My first such kit was a Guillow's Hawker "Hurricane," which I purchased
at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69 cents,
in 1966!

(Hey, that was a lot of money, for a 12-year-old kid, back then. g)

I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits
in the '40s. Comet kits were usually 10 cents as I recall, and that even
included a tiny glass tube of model airplane cement. Not enough cement to
actually put the plane together, unless perhaps you were very skillful at
economizing on it. Those 10-cent kits were of course the smallest of the
several sizes. Wing ribs and fuselage formers, etc., were all printed on a
thin sheet of balsa and had to be cut out my hand -- very hard to do with an
ordinary razor blade.

Hello, Neil:

My recollection of Comet, is that it churned out tons of garbage, during the
sixties and seventies. The company even sold pre-assembled, rubber-powered
planes, offering plastic fuselages and foil-covered balsa wings and tail
surfaces.

None of those pathetic products had any hopes of flying, whatsoever; they
were simply toys, rather than scale models.

At the opposite end of the quality spectrum, was Sterling. Its superbly
crafted kits contained precision, die-cut parts, silk span (instead of
ordinary tissue paper), nicely finished hardware (e.g., wire landing gear,
rubber wheels, etc.) and an in-flight "working feature." (This last item
could entail dropping bombs or leaflets, firing rockets, etc., depending
on the aircraft in question.)

Too kewl! g

I bought a number of kits but never succeeded in finishing one until finally
I completed a (somewhat larger) Fokker D.VII when I was about 16. That flew
reasonably well but I got tired of doing all that hand-winding of the rubber
motor for a very short flight. It wasn't until much later that I learned
about more serious modelers using a geared hand-powered drill to wind the
motors. That would have saved me a lot of aggravation.

Mostly as a kid I experimented with hand-launched gliders, made entirely of
balsa sheet and not requiring any of that tricky building. I didn't return
to stick and tissue models until the '60s or so, and then only briefly.

Yeah, those "North Pacific" cuties were loads of fun, and they could be had
for a nickel apiece!

Of course, the rubber-band birds ("Skeeter," "Sleek Streak," etc.) were a
bit more expensive...starting at the alarming price of a whole dime. ;-)

edited

Hip Pocket Aeronautics http://www.hippocketaeronautics.com


That site is interesting, but I can't seem to find anything there (or
elsewhere) about the slow-flying indoor models covered with microfilm. (I
*think* microfilm was what they called it, but it wasn't what you usually
think of as microfilm. I believe it was some sort of collodion, and the
method of covering wings and other surfaces, including the prop, was to pour
some of this stuff on water where it formed a thin film, and then pull the
framework of the wing or other surface up through it. Or so I understand; I
never built one myself.)

Whether "microfilm" is the correct term or not, those models' covering was
essentially transparent and weighed next to nothing -- much lighter than
tissue -- and it was amazing to see them fly. The big props would turn very
slowly, lazily, and the models would fly in large circles, climbing until
the rubber motor started to run down. They were so light and flew so slowly
that even flying into a rafter near the ceiling didn't damage them. They
were only flown indoors in some large space like a big gym or very large
aircraft hangar, as they could not have coped with even the slightest
breeze.

Regards,

Neil

As for myself, I only saw the "microfilm" babies in magazines. They always
struck me as somewhat bizarre, to say the very least. g


Cordially,
John Turco

tony cooper wrote:

On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington"
wrote:

edited for brevity

I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits
in the '40s. Comet kits were usually 10 cents as I recall, and that even
included a tiny glass tube of model airplane cement. Not enough cement to
actually put the plane together, unless perhaps you were very skillful at
economizing on it. Those 10-cent kits were of course the smallest of the
several sizes. Wing ribs and fuselage formers, etc., were all printed on a
thin sheet of balsa and had to be cut out my hand -- very hard to do with an
ordinary razor blade.

The first time I attempted to make a kit I glued several sections
together using a page of newspaper to protect the table. When I tried
to remove the glued sections, great chunks of newspaper came up with
the section.

Hello, Tony:

I did something similar, during my debut...as I'd failed to heed the
instruction sheet's advice, regarding the use of wax paper. :-)

Actually, if I recall correctly, I intentionally glued the balsa parts,
directly to the aforementioned sheet. It seems that I didn't know any
better, and was tackling a kit too advanced for my tender age. g

edited

I had a brief experience launching balsa sheet gliders from my
grandparents' second story porch. I'd glue a thick string of yarn to
the body, soak it with lighter fluid, light the plane, and send it off
to spiral down like the fighter planes in the RKO newsreels. Great
fun...until one landed on a neighbor's automobile's convertible top.
Luckily, it only scorched the top, and I was never caught. Never
tried it again, though,

Naughty, naughty! :-J


Cordially,
John Turco