On 27 Feb 2014 05:09:30 GMT, "DoN. Nichols"
wrote:
On 2014-02-27, wrote:
On Wed, 26 Feb 2014 18:07:01 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
fired this volley in
:
And then the "home" battery chargers - those that used Selenium or
copper oxide rectifiers - were ALL half wave. I replaced a few with
full wave bridges and they would boil a battery dry in a heartbeat.
That's pure BS, Clare. I've also used and repaired battery chargers for
nigh-on 52 years. They are ALL full-wave center-tapped, except for those
teensy little 2A maintenance chargers.
You either aren't saying what you mean, or don't understand a full-wave
rectifier like you think you do.
You can get full-wave without a 'bridge' -- just TWO diodes... and that
ain't half-wave.
Lloyd
I know full and half wave. Without a center tapped transformer you
need a bridge for full wave. That's 4 diodes. With a center tap, you
need 2 diodes and you have full wave. With only one diode and one
winding you have half wave.. If you put a single diode on a center
tapped transformer and don't use the center tap, it's hald wave.
If you put a single diode on a center tapped transformer, and
don't use the center tap, you are applying twice the design voltage to
the battery -- so you *will* get overcharging then for sure -- or burn
out the transformer first. :-) If you put a full wave bridge rectifier
on the unit, and still leave the center tap floating, you will have not
quite as high a voltage, but current closer to full time, and will also
overcharge.
However -- using the full-wave bridge between the center tap and
one side of the transformer will produce something closer to the design
voltage -- but you will be drawing all your current from one half of the
secondary -- and if the design is marginal, you will again burn out the
transformer. With two diodes wired as the original selenium rectifiers
were will get a little more voltage out, but not much. Probably swamped
in the loss in the transformer.
Anything using a single standard tungar tube was half wave (and yes,
I've used and worked with Tungar chargers). There were full wave
tungar bulbs for center tapped transformers,(twin anode) but they were
high voltage low current devices, generally not suitable for
automotive battery charger circuits. Some chargers were multi-tube
units as well, but in my experience they were not very common (I've
never used one or seen one in use).
Tungar is rather old technology these days. The last time I saw
those in use was in the power supply for a drive-in movie projector back
in the very early 1960s.
Selenium rectifiers have been used in battery chargers for decades,
and are still common on the cheap home chargers. Single plate seleiums
are good for 25PIV, have a 1 volt per plate forward drop, and have
regulating characteristics that make them a good choice for a
low-compnent-count charger. Copper oxide was used for the same
purpose quite a few years back, but they are less efficient (although
lot more efficient than Tungars).
Of course.
I've pitched quite a few 6-10 amp chargers with single plate seleniums
over the last 20 or more years - so they are still pretty common..
Some use the chassis as the heat sink AND cathode - with just a rivet
through the wire terminal, plate, and chassis.
Same construction on some of the full wave center tapped chargers.
Indeed -- which is why the selection of diodes with either
standard or reverse stud polarity could allow it to work closer to its
original design.
Don't set one of those on the fender of a positve ground car!!!!
It could get exciting -- especially once you scratch through the
paint. :-)
I've also tried replacing the seleniums with silicon stud-mounts -
with poor results. A single silicon diode with 25 or 50 PIV rating has
about a .7 volt forward drop, so you would thing the charge rate would
be pretty well the same - but I found they tried to charge at a higher
current - causing the current interupter (breaker) to cycle - and
putting in a bridge raised the voltage.
If as you said near the top, you were not using the center tap,
yes it would raise the voltage quite a bit. :-)
Nope. With center tap I would use 2 - but this particular one was a
single plate unit. Using a bridge put the voltage too high,
Into a straight resistive load
a full wave circuit produces very close to double the voltage a half
wave puts out.
That is, again, if you are not using the center tap. If you use
the center tap, and half of a full wave bridge (two diodes, the other
bridge output terminal not connected to anything) you will be closer to
the design voltage.
Again, I was taliking the single plate charger. If you have a center
tapped transformer it is pretty hard to use a half wave or a bridge
properly.
And regardless, the silicon diode has NO regulation effect at all,
while a selenium plate does. The selenium plate rectifier is "softer"
than a silicone - to properly emulate a selenium rectifier you NEED to
put a low value resistor in series.
You could use the full-wave bridge between one side of the
transformer and the center tap (and leave the other side floating) your
voltage would be closer to normal.
and using a bridge on one side of a center tap would be too low to
charge the battery effectively
In a capacitive circuit it is a bit closer, IIRC. - but
still no good for a simple battery charger.
No need for (filter) capacitors on a battery charger in normal
use, the battery itself sort of handles the filtering there if it is
still good.
Like I said, the capacitive effect of the battery in the circuit
makes the voltage a bit closer to correct - but still not good enough
for a "simple" battery charger.
The pulsing of a half wave rectifier in a battery charger, according
to some people, has less of a polarizing effect - making for more
efficient? charging because the plates don't get covered with bubbles
of H and O2 as much. Works a bit like the "desulphators"
Maybe. I don't know there.
Anyway - suffice it to say there have been ALL KINDS of different
battery chargers - with all kinds of circuits, used over the decades.
From terribly crude, badly regulated to very refined and well
regulated - using everything from Fero-resonant regulation to
mechanized carbon pile regulators to fully electronic regulation -
solid state and otherwise.
Quite a collection.
My favorite charger was a dynamotor setup - 1/2 horse electric motor
running an old autolite generator with 2 voltage regulators on it and
a switch to connect either the 6 volt or the 12 volt regulator.. It
was one you could connect and walk away, knowing the battery would be
fully charged and not overcharged when you returned.
Sounds interesting. Not as efficient as some other circuits,
but yes, free of overcharge. Same should be do-able with an alternator
and the appropriate regulator as well.
Not nearly as noisy and stinky as the gasoline powered unit used for
charging and boosting cars on the used car lot (3hp Briggs and a
motorola? alternator)
:-)
Enjoy,
DoN.