Author Topic: Capacitors; Why 6.3V?  (Read 1774 times)

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Offline chris_leyson

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Re: Capacitors; Why 6.3V?
« Reply #25 on: October 24, 2020, 01:39:20 pm »
Way back in the day my grandfather would take his lead acid accumulators down the road to the chemist to get them recharged. This would have been 1920s or 1930s so I'm guessing two valve regen receiver with 2V heaters or maybe 1V heaters in series. In the 50s he managed to save up enough for a LW/MW/SW mains powered receiver, might have been a Murphy. Back then SW was like the internet but in one direction.
 

Offline TimFox

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Re: Capacitors; Why 6.3V?
« Reply #26 on: October 24, 2020, 02:06:18 pm »
I am curious about how that was handled in practice.  Did the chemist have a motor-generator set operated off the local mains, or did he use a gasoline-powered device to charge accumulators for customers?  I remember old-fashioned "Tungar bulb" (gas-filled tube) rectifiers for battery chargers which were available in the 1920s.
 

Offline mag_therm

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Re: Capacitors; Why 6.3V?
« Reply #27 on: October 25, 2020, 12:36:56 am »
I am curious about how that was handled in practice.  Did the chemist have a motor-generator set operated off the local mains, or did he use a gasoline-powered device to charge accumulators for customers?  I remember old-fashioned "Tungar bulb" (gas-filled tube) rectifiers for battery chargers which were available in the 1920s.
In 1940'~50's Australia my father had an auto dealership in a town that had 240 V DC local utility, and owned the electrical generation in another town that was 110 VDC powered by Ruston-Hornsby ( UK) D-Generators.
Domestic radios at that time could not run on the residential DC reticulation.

In the auto dealer garage was a small room for battery charging.
A double ended brushed DC machine with a small control panel powered dual busbars , one was for 6V batteries and one was for 12 V batteries.
The equipment was made by Hobart of Ohio USA. Customers would bring their wet 6V radio filament batteries and tractor batteries etc for charging.
I recall that wooden racks were usually full of batteries on charge, and I was taught how to use the battery hydrometers.
 
The dry plate batteries were maybe 90 V by EverReady.
The radios (there was one in our living room) had both batteries in the bottom of the cabinet.

When TV came, they could not run on DC, so homes had either OAK (UK) vibrating contact inverters, or small double ended machines to get 240V AC.
 

Online Circlotron

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Re: Capacitors; Why 6.3V?
« Reply #28 on: October 25, 2020, 04:57:19 am »
DIY contsruction details from an early 30's book I have for two battery chargers, one for DC mains and the other for AC.
 

Offline Zoli

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Re: Capacitors; Why 6.3V?
« Reply #29 on: October 25, 2020, 05:26:07 am »
Reminds me of when I was asking why you can get fuses rated at 3,15A.
Because is right between sqrt(10) and pi... >:D >:D >:D
 

Offline TimFox

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Re: Capacitors; Why 6.3V?
« Reply #30 on: October 25, 2020, 02:13:13 pm »
To Circlotron:
I like the first idea in the article (obviously for DC households) to merely wire the battery in series with a house light for a slow charge.
 

Offline wizard69

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Re: Capacitors; Why 6.3V?
« Reply #31 on: October 26, 2020, 05:05:20 pm »
One thing to consider with respect to 24 VDC is that it is a fairly common voltage in military vehicles and heavy construction (large engine vehicles).    The obvious need here is to have a starter motor that can turn over a much larger engine than is common in cars.

As for 6 VDC that was fairly common in early agricultural equipment.   However it did work out all that well.   This gave rise to the 8 VDC lead acid battery specifically to power this farm equipment.   Most farm equipment these days is 12 VDC except possibly on the biggest machines out there.

The other place 24 VDC has become popular is in industrial controls.    It is a voltage low enough to be considered safe in most uses and areas.   On the other hand the voltage is high enough to break down oxides on contacts in switches and such.
 

Offline ssashton

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Re: Capacitors; Why 6.3V?
« Reply #32 on: October 27, 2020, 06:55:48 pm »
Wow thanks for all the replies!

In short it seems like the origin is battery voltages. However 6.3V is pretty convenient for 5V rails.

63V I guess is just a weird one that exists as a multiple of 6.3V? 48V rails could be run with 50V caps, although the safety margin is smaller, but we all know there is more to cap life than the voltage rating.
 

Offline Wallace Gasiewicz

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Re: Capacitors; Why 6.3V?
« Reply #33 on: October 27, 2020, 07:24:02 pm »
Even though we now have reasonably cheap DC/DC converters, it is a real bear to install a 12 volt CB radio in a model A Ford.
The Model A club guys and gals use the radio to keep in touch while driving to meets and other activities.
I suppose other antique auto people use them also.

Wally
 

Online james_s

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Re: Capacitors; Why 6.3V?
« Reply #34 on: October 27, 2020, 07:24:35 pm »
I wouldn't use a 50V cap on a 48V rail. Even with modern regulated power supplies that's much too close for comfort. When dealing with batteries that would be 12 lead acid cells, which could be as high as 2.3V fully charged or 55V for the whole bank and potentially higher than that while charging. Unregulated supplies that were once very common have a similar issue, a 48V power supply could easily reach 60V under no load or when the line voltage is running a bit high. Even a (linear) regulated supply is going to need to have a bulk capacitor before the regulator.

A related question that comes from this is where did the 5V used for logic come from? Was it a convenient voltage that could be produced by a common 6.3V transformer?
« Last Edit: October 27, 2020, 07:27:40 pm by james_s »
 


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