What's A "Timber bulb"?

[DaveMcLain]

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...

[leadbelly]

Search for a "tungar" rectifier.

[aardvarkash10]

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!

[tubelab.com]

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.

[DaveMcLain]

Thanks guys I appreciate the information. I had heard him talk about that before and now I know. Quite an interesting idea actually.