My car battery is oversized for the car. The battery is a bit old but usually works fine. The battery is flat (I left the lights on).
My fancy new modern charger senses a poor battery and only puts in very little charge.
I used to use a really old charger to charge this battery successfully. I opened up the old charger and saw it was only a transformer and a big rectifier. That's it. No soothing.
Is this ok for a car battery or is it way too crude?
Not *too* many years ago (mid 70's), my dad had to retire his battery charger. The filament for the edison valve finally burned out and there are no replacements.
120 VAC to a transformer with two secondary windings. One powered valve filament, the other when to cathode and positive cable. Negative cable came from plate of the 'valve'.
Worked fine for many years (originally purchased by my grandfather back in the 20's or 30's).
daestrom P.S. Mind you, you did have to keep an eye on the battery and when it started bubbling/boiling, it was time to shut it off (big ole rotary snapswitch on the line side)
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "daestrom" saying something like:
Would have been a simple job to put in a normal solid state rectifier, just to keep a historically interesting bit of kit working. Otoh, valve rectifiers are still being made in China, afaik.
I suspect it was something like a Tungar argon rectifier or a mercury vapor rectifier and not a conventional thermionic diode as is still made today for tube (valve) audio and such. You need something low impedance for a battery charger.
All I can remember is that it looked remarkably like a large, old-fashioned, light-bulb. Had a screw-in 'Edison' bulb base as well. The only difference was a single heavy wire also ran to a terminal at the top of the bulb, opposite the base. The terminal entered the glass and ended in a simple, flat plate above the bulb filament.
Remember thinking it was just like I had read in a book on Edison about how he first discovered the 'Edison effect'. That a heated filament would give off electrons to a positively charged plate.
Tungar rectifiers are certainly less efficient but they cannot be directly replaced by semiconductors because the voltage drop is much different, several volts for a Tungar and the charger would then produce too hi an output voltage.
While the 'bulb' shown looks familar, the charger in question didn't come in a box like that. As I recall it hat a rotary snap switch on the front and a circular tapped switch to adjust the charging current and one rather old-fasioned ammeter. Turned it on and checked the current, adjusting the tap to suit.
But that definitly looks like the 'bulb' :-) Thanks for the memory jogger...
With a forward drop of something like 0.7 volts how many do you need in a stack to get towards the 6 or 7 volts forward drop of a tungar and why would you need a stack to get a reverse voltge of a mere 20 volts.?
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