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VK3ABK > TECHNI 17.08.04 03:31l 111 Lines 4282 Bytes #999 (0) @ WW
BID : 32391_VK3KAY
Read: GUEST OE7FMI
Subj: More Battery Confusion.
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Sent: 040817/0115Z @:VK3KAY.#WEV.VIC.AUS.OC #:32391 [Wendouree] $:32391_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : TECHNI@WW
Hello to all Confused.
The recent comments from two of the most confounding writers imaginable, is
making a mockery of my original title, "Battery Confusion". I had no idea
that a simple subject could be so confounded confusing!
As Jeff has written....
Andy, GM7HUD wrote:- (To G4XNH)
"So Jeff, if your alternator cannot provide the current to drive the
headlamps where does the current come from."
Jeff's 'answer'....
It came from nowhere Andy. The engine stopped when the headlights were
switched on so nothing was required.
( You didn't read (or understand) the question, Jeff.))
Jeff continued....
An alternator certainly could not provide the alleged 200 Amps or 300 Amps
usually required to turn an engine over, albeit drawn for only a very
short period to break the inertia of the engine.
(No-one said anything about 'starting' the car from the alternator.)
From Andy, via Jeff....
"So where does the missing current come from to replenish the charge in
the battery as the battery is "topping up" for the alternator, which will
not drive the headlamps?"
Jeff's reply....
I am not quite sure that I understand that question Andy.
(qed)
(There is more, but Jeff gets more and more confusing the more he writes!
What else is new? Come on Jeff, answer the question without the semantics.
No-one is trying to de-dowse you. Impossible! "What more can I say"!!!)
--------------------------------
Now, consider this from 'you know who'.
In a monstrous piece of technical tripe from the windy coast, I read....
Hi John and readers,
"....I wired up a line isolation transformer, a 100 Ohm 2W carbon resistor
and a 1uF capacitor in series and a whole lot of battery clips, also in
series. You don't need a print, everything on the secondary side is connected
in series. Oh, forgot the bridge rectifier, hi. Since in the US the peak
mains value is about 160V any number of cells in series may be charged up to
slightly less than that value. All unused battery clips were bridged by short
jumper (crocodial) clips."
(Now I'm confused! Here we are told that a circuit with Resistance and
Capacitance in series will give the 'lucky' experimenter, current for his
home-made battery charger. As I see this arrangement, we either have a
'reactive' circuit (containing capacitive reactance) in which case the phase
shift will affect the 'charge', or 'not forgetting the bridge rectifier' we
will have an ineffective 1uF capacitor in a DC circuit.)
(What an interesting problem for this author to explain.
By the way, I still don't understand the 'dead battery-sulfating trick' in a
previous bulletin. Any comment?)
Then we read....
"The key to Tony's charger and mine is it's the CURRENT that charges the
battery, the only consideration given the voltage is that it must be
above the fully charged, open circuit battery terminal value so that
current flows. .... Since this is a high voltage method it must be compared
to the low voltage method for current limiting to be fully understood."
(I'm not sure of the point being floated here. Please explain!)
"Start with Ohm's Law and you're off BUT still some form of limiting must be
considered with low voltage. There are two ways of doing it. In high current
chargers a split core (saturable) transformer is used while the typical home
charger uses the DCR of the secondary winding. In other words the transformer
design is the key here, no external devices are needed."
(Ah, Yes! Ohm's Law. Everyman's friend-in-need. And so simple too! But the
old saturable reactor trick introduces 'higher mathematics' so, FYI...... ?)
"Yes, the beauty of the poor man's charger is twofold, it's simplicity and
versitility. You can charge from one to as many cells as you want totalling
up to only slightly lower than the open circuit charger output. Just watch
your fingers, it bites even when unplugged, the cell voltage DOES add up."
(Like they say in the how-it-works pages, DON'T TRY THIS AT HOME.)
Now, I'm not complaining; we have seen some helpful advice and something
new in car care and operating on dangerous ground, so all is not lost.
But the best explanation of a problem is usually the simplest (and correct).
Confusingly....
73. Dick. VK3ABK.
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