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Old 28th April 2009, 01:08 AM   #1
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Default What's A "Timber bulb"?

My dad has told me that back in the old days they used something called a tumber or timber bulb to charge car batteries. The charger was mounted on the wall and you could just hook up as many batteries as needed charging and the charging rate would be determined by the load presented by the batteries. He said that the timber bulb which must have been some sort of high current tube rectifier lit up and was the heart of the whole thing. Has anyone got any information about this?

Gas stations and auto parts stores used them before about 1960 or so...
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Old 28th April 2009, 01:29 AM   #2
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leadbelly's Avatar
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Location: Calgary, Alberta
Search for a "tungar" rectifier.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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Old 28th April 2009, 01:56 AM   #3
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Location: Auckland, NZ
Default good lord...

I'm old enough to remember one! Yeah, essentially a constant current device. Most battery chargers are constant voltage, and batteries are connected in parallel accross the charger. The valve rectified constant current charger allowed you to connect any number of batteries in any series configuration so they were great for maintaining charge on a large number of batteries eg units for sale and held in stock. 6 volt or 12 volt, didn't matter... Ours had a really dodgy carbon pile for setting the charge current!
"It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,
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Old 28th April 2009, 02:24 AM   #4
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The device is called a "Tungar bulb". It looks like a large fat light bulb with a plate on one end. Most had a "Mogul" screw in base like a large light bulb, although I have seen them with fat wire leads. The filament is a low voltage (6V was common) so never screw one into a common light socket.

It is essentially a half wave directly heated rectifier tube capable of passing an amp or more of current. The filament emission is the limiting factor which is responsible for the current limiting effect.
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Old 28th April 2009, 12:10 PM   #5
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Thanks guys I appreciate the information. I had heard him talk about that before and now I know. Quite an interesting idea actually.
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