Winter is the easiest time for me, no bugs, few outdoor chores, cooking and boiling-hot water are free and raw vegetables keep in the garage. Laundry dries on the line nearly as quickly as in summer because the humidity is low, 44% right now. My house will remain at least 30F warmer than outdoors without a fire during a sunny day.
It's for safety; if you get shocked you stop cranking. They have a centrifugal clutch that limits the maximum RPM and voltage. The shorted output current on this one is only 1mA but if you are using it to reform an old high-voltage electrolytic cap you can still get hurt. I was nailed by 10uF at 800V once and don't care to repeat it.
except it has mA under the A, and resolves to 1mA in the Low, 0-1A range. The control decal is yellow. It's heavy enough to be a linear and a relay clicks several times as I turn the voltage up. jsw
I've worked as a mechanic for many years, and have run and repaired battery chargers much older than myself - MANY of which had simple half wave rectifiers. 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.
They were designed to charge at about 18 volts open circuit on the high current setting, and about 14 or 15 on the low current setting - and the resistance of the circuit (largely the rectifier on the old seleniums) helped limit the charging current when the battery was taking a heavy charge.
Our old Marquette and Allen chargers ( or was it the "silver beauty?) had a timer for the high charge, and a low charge that stayed on after the timer shut off if selected.
Then there was the "constant current" slow charger that could charge from 6 to 60 cells at a time - all in series.
snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:
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.
I am confused. How is the voltage increased by the virtue of full wave rec tification? I can see the current increased, but not the voltage. Silicon d iodes do have less voltage drop than selenium diodes. It has been way too many years since I had anything to do with selenium rectfiers. As I rememb er the voltage drop depended on how many plates there were used in order to get the necessary reverse breakdown. So for a 12 volt battery charger, no t that big a deal.
In any case using silicon diodes in place of selenium should be no big deal in Tom's case where he uses the repaired battery charger to partially char ge a dead battery and then changes to his new modern electronic charger.
I am off to refresh my memory on selenium rectifiers. As I remember the na vy purged all the selenium rectifiers from their equipment back in about 19
60, because the fumes from a burned out selenium rectifier were poisonous.
Gee... don't battery chargers have current adjusting knobs on them any more.
Mine must be an antique, or something. Got a selector switch, 12 or 24 volt battery, and another knob to select the amount of charging current and even an ampere meter to tell you how much you are charging.
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. 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).
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). 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.
Don't set one of those on the fender of a positve ground car!!!!
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. Into a straight resistive load a full wave circuit produces very close to double the voltage a half wave puts out. In a capacitive circuit it is a bit closer, IIRC. - but still no good 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"
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.
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.
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)
IIRC Half wave gives about .3 X AC voltage and full wave closer to .6 times becuse full wave puts both halves of the sine wave to work, while half wave only uses half of it.. Can't remember it that was peak or RMS (on the AC side). And yes, those seleniums REALLY stunk when they let go. Selenium is a very close relative of sulphur chemically, and selenium dioxide and sulphur dioxide have similar smell and effect -EXTREMELY unpleasant. And poisonous. Burns skin and mucosa - and eyes.
I got bitten by an 800v line inside a computer monitor once. That really smarts. I could feel scar tissue in the heel of my hand for a couple years afterward.
Reasonable. But given that the battery charger in question used only two (selenium) rectifiers (and a center-tapped transformer secondary), there is no need for the other half of the rectifier assembly -- and it takes up space, so pull out one plate and only mount the one which has the flavor of diodes (normal or reverse) needed by the design of that battery charger. And with that, you probably don't even need the insulating strips to insulate it from the chassis. Since he said that there was only one wire going to each selenium rectifier, I suspect that the chassis is serving as the common point of the two rectifiers.
And -- a use for the extra rectifier place could be to swap in one from the other plate (reverse or standard -- the opposite of what is on the plate with the needed rectifiers) to block against reverse connection to the battery frying the transformer or the diodes -- or both.
Have you looked up the current rating for those diodes? Given the cable leads instead of terminals, I suspect that it is rather impressive. :-)
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.
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.
Of course.
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.
It could get exciting -- especially once you scratch through the paint. :-)
If as you said near the top, you were not using the center tap, yes it would raise the voltage quite a bit. :-)
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.
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.
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.
Maybe. I don't know there.
Quite a collection.
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.
You missed his statement that he was ignoring the center tap, so applying double the AC voltage to the bridge. Having the half-wave relative to the center tap produces half the peak voltage that using a full wave bridge with the center tap floating.
Agreed -- until you start using the transformer's end-to-end voltage without the center tap involved.
Agreed -- a single plate per side of the transformer.
Agreed.
And nasty smelling, too, even with a relatively small one. I never used a large enough one for the fumes to be a problem -- and I was a kid (thus indestructible) back then anyway. :-)
We drop to 0 at night but haven't had a day that stayed that cold. If the house was at 60F in the morning and the day never rose above 15F the house might lose 2-3 degrees during the day without a fire. It's hard to measure accurately because I raise the thermometer about 1 to
1.5 degree from normal activity, making breakfast and running the computer, and the basement holds and slowly releases a lot of wood stove heat. My preliminary test runs revealed a few things to change before making better measurements.
I do know that a single 700W baseboard heater will hold the house well above freezing without costing a lot. That was the important question. The insurance company wanted to be sure I had automatic backup heat, not just the stove.
This is a standard housing-development electrically heated home from
1970 and about all I've done is reduce heat loss through the doors and windows and add more attic insulation.
I ripped out the 240v baseboard heaters and plopped down $6k for a Carrier Infinity (96% efficient) heater and A/C unit shortly after I moved into this 1966 era home. The single-glazed aluminum-framed windows went and Low-E dual-paned vinyl windows really quieted things down and warmed things up for me.
You're better insulated than I am. The last time the power was off in Winter, I think I lost 1.5F per hour.
One of these days, I'll pull the top clapboards off, drill holes, and pump the walls full of glass. I put R-38 under the house a few years ago when I had it Visqueened and borated. And there's a meager 6" of fluff in the attic. That will have to come up, too. I finally got up there last week and got myself very sore, climbing around installing
12v wiring through the ceiling for the emergency solar lighting.
Tomorrow, I mean to go up and hook in the last line, from the controller. My roof is 4:12, so there is only 4ish feet of headroom at best. I don't know how many more attic trips the old bod is capable of in the future, but it ain't many, I tell ya.
I found the last heat leaks by watching the melting pattern of light snowfall, and scanning the inside walls and ceiling with a cheap IR thermometer. The windows glass and Mylar film reveal their temperature to the IR thermometer by sticking on black tape.
I have a roof like that. The last time I could work comfortably in the attic was when a fallen tree knocked a dozen large holes in the plywood. OTOH my beer didn't slide off when I was reshingling.
My emergency solar lighting is a pair of HF solar lanterns. I really only need to see the floor to walk around at night.
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,
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.
and using a bridge on one side of a center tap would be too low to charge the battery effectively
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.
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