Author Topic: How did battery chargers rectify AC to DC before solid state diodes?  (Read 2712 times)

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Offline Connecteur

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #50 on: April 21, 2021, 04:22:45 pm »
Rotary converters have always been an option, but not always a cost-effective one.  I think most big radio installations through WWII used DC generators to recharge the batteries.  The need to use AC power to charge batteries was for the average consumer who couldn't afford expensive rectifiers or rotary converters, so I'm curious about how they charged batteries in those days.
 

Online janoc

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #51 on: April 21, 2021, 04:36:17 pm »
Rotary converters have always been an option, but not always a cost-effective one.  I think most big radio installations through WWII used DC generators to recharge the batteries.  The need to use AC power to charge batteries was for the average consumer who couldn't afford expensive rectifiers or rotary converters, so I'm curious about how they charged batteries in those days.

You are assuming that an average consumer in the early 20th century actually needed to charge batteries. The only somewhat common thing that needed batteries back then was a tube radio. Which was a luxury item few had. Those radios if battery powered used normal primary, non-rechargeable, cells.

Rechargeable batteries were only used later and mostly for industrial uses. Even cars didn't have rechargeable batteries (not counting the few electric cars which were rather obscure oddities), they only became more common around 1920 or so. And those originally used 6V batteries charged with dynamoes, vibrating rectifiers and later selenium rectifiers.

Electronics became more affordable for the average consumer only after WWII and then the semiconductor diodes existed already (selenium rectifier was invented in 1933), as did vacuum diodes. But even then there wasn't much on the market that could use a rechargeable battery back then.

Also, keep in mind that the only rechargeables commonly available were wet lead acid batteries (NiCd didn't really appear only after the war and was expensive), that's not something you would lug around unless you didn't have other choice.
« Last Edit: April 21, 2021, 04:53:31 pm by janoc »
 

Online BrianHG

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #52 on: April 21, 2021, 04:50:02 pm »
Rotary converters have always been an option, but not always a cost-effective one.  I think most big radio installations through WWII used DC generators to recharge the batteries.  The need to use AC power to charge batteries was for the average consumer who couldn't afford expensive rectifiers or rotary converters, so I'm curious about how they charged batteries in those days.
Did you not watch the video I posted a few messages back:
https://www.eevblog.com/forum/beginners/how-did-battery-chargers-rectify-ac-to-dc-before-solid-state-diodes/msg3552749/#msg3552749
A dirt cheap 120v AC in, 6v 5 amp DC charger available in the 1920's.
« Last Edit: April 21, 2021, 04:52:37 pm by BrianHG »
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Online janoc

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #53 on: April 21, 2021, 04:52:36 pm »
Did you not watch the video I posted a few messages back:
https://www.eevblog.com/forum/beginners/how-did-battery-chargers-rectify-ac-to-dc-before-solid-state-diodes/msg3552749/#msg3552749
A dirt cheap 120v AC in, 6v DC charger available in the 1920's.

Nice old car battery charger.
 

Online BrianHG

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #54 on: April 21, 2021, 04:55:11 pm »
And it's DC rectifier is powered by Vibranium.
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Offline Connecteur

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #55 on: April 21, 2021, 05:23:43 pm »
In the first half of the 20th century, there were a lot of radio installations, used to relay messages for the military and others. They used big banks of lead-acid batteries, and I'm sure the most cost-effective way to charge them was with DC generators.  I suppose in more settled areas with AC power they used a few rectifiers,   but I assume generators were the preferred option for a long time.
 

Offline Connecteur

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #56 on: April 21, 2021, 05:26:24 pm »
Rotary converters have always been an option, but not always a cost-effective one.  I think most big radio installations through WWII used DC generators to recharge the batteries.  The need to use AC power to charge batteries was for the average consumer who couldn't afford expensive rectifiers or rotary converters, so I'm curious about how they charged batteries in those days.

You are assuming that an average consumer in the early 20th century actually needed to charge batteries. The only somewhat common thing that needed batteries back then was a tube radio. Which was a luxury item few had. Those radios if battery powered used normal primary, non-rechargeable, cells.

Rechargeable batteries were only used later and mostly for industrial uses. Even cars didn't have rechargeable batteries (not counting the few electric cars which were rather obscure oddities), they only became more common around 1920 or so. And those originally used 6V batteries charged with dynamoes, vibrating rectifiers and later selenium rectifiers.

Electronics became more affordable for the average consumer only after WWII and then the semiconductor diodes existed already (selenium rectifier was invented in 1933), as did vacuum diodes. But even then there wasn't much on the market that could use a rechargeable battery back then.

Also, keep in mind that the only rechargeables commonly available were wet lead acid batteries (NiCd didn't really appear only after the war and was expensive), that's not something you would lug around unless you didn't have other choice.


Good point. The average farmer probably didn't worry about charging batteries when he could crank-start everything.  I suppose a battery charger might be more useful in a small business where there was a demand for charging batteries for customers.
 

Offline Connecteur

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #57 on: April 21, 2021, 05:29:13 pm »
I don't think electric cars were always an oddity. 28% of all cars in the US in 1900 were electric:
https://www.businessinsider.com/electric-car-history-2017-5#the-electric-car-burst-onto-the-scene-in-the-late-1800s-and-early-1900s-1
 

Offline james_s

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #58 on: April 21, 2021, 06:15:50 pm »
Rotary converters have always been an option, but not always a cost-effective one.  I think most big radio installations through WWII used DC generators to recharge the batteries.  The need to use AC power to charge batteries was for the average consumer who couldn't afford expensive rectifiers or rotary converters, so I'm curious about how they charged batteries in those days.

You are assuming that an average consumer in the early 20th century actually needed to charge batteries. The only somewhat common thing that needed batteries back then was a tube radio. Which was a luxury item few had. Those radios if battery powered used normal primary, non-rechargeable, cells.

Rechargeable batteries were only used later and mostly for industrial uses. Even cars didn't have rechargeable batteries (not counting the few electric cars which were rather obscure oddities), they only became more common around 1920 or so. And those originally used 6V batteries charged with dynamoes, vibrating rectifiers and later selenium rectifiers.

Electronics became more affordable for the average consumer only after WWII and then the semiconductor diodes existed already (selenium rectifier was invented in 1933), as did vacuum diodes. But even then there wasn't much on the market that could use a rechargeable battery back then.

Also, keep in mind that the only rechargeables commonly available were wet lead acid batteries (NiCd didn't really appear only after the war and was expensive), that's not something you would lug around unless you didn't have other choice.

There were lots of rural areas in the USA that did not have electrical service until after the WWII era. It was not uncommon to have a flooded lead-acid battery bank to use for electric lighting and a radio, there were quite a few "farm radios" made to run off 32VDC. They would use an engine powered generator to charge up the battery bank, or occasionally a windmill. I don't know how common it was to have such a setup but farm radios are not super rare.
 

Online janoc

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #59 on: April 21, 2021, 06:28:54 pm »
I don't think electric cars were always an oddity. 28% of all cars in the US in 1900 were electric:
https://www.businessinsider.com/electric-car-history-2017-5#the-electric-car-burst-onto-the-scene-in-the-late-1800s-and-early-1900s-1

Lol, and from how many were those 28% calculated?

Here is the full quote:

"28 percent of all 4,192 cars produced in the US in 1900 were electric"

So that makes a whopping 1200 cars or so, for the entire country. How many people in the US saw a car during that era, even less owned one? And also had AC electricity to boot, so that they would actually become relevant for the OP's question? I would say that not many ... So yes, it was an obscure oddity - not because it was electric but because such "horseless carriage" was so rare.

« Last Edit: April 21, 2021, 06:32:47 pm by janoc »
 

Offline ejeffrey

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #60 on: April 21, 2021, 07:40:30 pm »
The term “generator” is now generic, including DC, AC, noise, RF, etc.
I remember when alternators (with solid-state rectifiers) replaced generators in automobiles, and that was the distinction.
“Dynamo” is still restricted to mechanical generators with a commutator to produce DC.

That was a distinction only really ever made in the context of automotive generators to distinguish the new AC generators with regulated field windings from the old DC generators whose output voltage depended on rpm. It's not some universal definition widely accepted outside the field of "the name of the part that recharges the 12V battery In a car".  Even modern cars use the phrase generator when referring to things other than the specific part that is an alternator, such as the "motor generators" in the Toyota hybrid drive train.
 
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Offline vk6zgo

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #61 on: April 22, 2021, 02:52:48 am »
In the first half of the 20th century, there were a lot of radio installations, used to relay messages for the military and others. They used big banks of lead-acid batteries, and I'm sure the most cost-effective way to charge them was with DC generators.  I suppose in more settled areas with AC power they used a few rectifiers,   but I assume generators were the preferred option for a long time.

Remember "the first half of the 20th Century " takes you right up to 1950.
Things changed with breakneck speed in that first half century.

Certainly, by  the 1930s, the large radio installations in Australia used AC power, either off the grid, or locally generated.

Tube transmitters of any reasonable power output require high voltage anode & often screen grid voltages.
The easiest way to obtain these was with HT transformers & mercury vapour rectifiers.

There were Broadcast Stations which used the DC mains, but they were often limited in power output, or did use motor inverters.

Broadcast and/or Comms Transmitting sites were very costly to put together, & needed Emergency Power Plant.
An AC EPP is less costly than a DC one, both in construction & maintenance. (slip rings & their associated brushes don't wear as rapidly as their commutator counterparts).

Some Radio Broadcast sites ran completely on their own locally generated AC, as there were no Mains supplies either AC or DC in the area.

6WA, in Wagin Western Australia, is a case in point, where the Radio Techs & Diesel Mechanics lived in a little "village" onsite.

The Diesels required a method of starting, which could be compressed air, or batteries.
It was often the latter.

In any case, even if the larger battery banks required for electrical starting were not needed, it was common to reticulate 24v DC throughout the building to handle those functions which needed to be maintained during a power break.
This was normally derived from the AC mains during normal operation, automatically switching to battery during power loss.

As copper-oxide, selenium, & Tungar rectifiers were inefficient, the chargers had large stepdown transformers, very big rectifiers, & hence the whole assembly was big.

There tends to be an assumption that, as new technology was developed, the "old hat" stuff was dumped, & replaced with the "latest & greatest".
After around the "Thirties" this was far from the case, as very few organisations were eager for the capital outlay to replace perfectly capable, reliable equipment, to gain a few percent of efficiency.

« Last Edit: April 22, 2021, 02:55:13 am by vk6zgo »
 

Offline The Electrician

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #62 on: April 22, 2021, 04:43:03 am »
The active junctions of copper oxide or selenium rectifiers of the construction were restricted to the small "washer like" area which was actually in compression.(see the photos in your link)
This is not correct.  See this image from page 6 of the Federal Selenium Rectifier Handbook: https://worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf

The full area of the plates are rectifying junctions (although the one pictured indicates that the "washer like" area is not part of the rectifying area).



[attachimg=1]
« Last Edit: April 22, 2021, 04:50:07 am by The Electrician »
 
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Offline vk6zgo

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #63 on: April 22, 2021, 06:25:53 am »
The active junctions of copper oxide or selenium rectifiers of the construction were restricted to the small "washer like" area which was actually in compression.(see the photos in your link)
This is not correct.  See this image from page 6 of the Federal Selenium Rectifier Handbook: https://worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf

The full area of the plates are rectifying junctions (although the one pictured indicates that the "washer like" area is not part of the rectifying area).



[attachimg=1]

That is very interesting!
Further reading on these devices prior to your posting made me wonder if my simple explanation might have been wrong, & you have shown I was!

Some other information on copper oxide rectifiers:-

https://de.zxc.wiki/wiki/Kupferoxydul-Gleichrichter

They point  out in this link that they were in large scale production as early as 1925.

The other important rectifier type in the pre-WW2 period is the Tungar rectifier:-

https://drive.google.com/file/d/1SsLvNLf99BWvNgQxZ3moB6dOTfefDRQv/view

The Tungar charger in the video looks like the one I had in the early '60s to charge my 1936 Chev's  6 volt car battery, except mine was, from memory, painted black.

They were invented in 1914, & went into commercial service in 1917.

From the above, both types of rectifiers were available for use in battery chargers from quite early in the 20th Century.

For battery charging, many people still lived with DC Mains power.
Batteries could be charged from 110v DC with a large series resistor, or series lightbulbs, etc, so the need to convert from AC to DC for chargers was confined to those areas with an AC supply.

In those areas, I think that rotary converters from AC to DC would mainly only have been viable to drive large DC motors in lifts (elevators), Industrial processes, trams (streetcars) & electric trains.

As everyday sources of DC for battery charging, they would, maybe be of use for very fast charging of large battery banks, which is not a common requirement.






« Last Edit: April 22, 2021, 06:28:04 am by vk6zgo »
 

Offline tooki

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #64 on: May 03, 2021, 04:20:20 am »
Nomenclature detail:  strictly, "generators" make DC and "alternators" make AC.
Perhaps in the automotive context, but not in general. I agree with coppice's assessment that the term "generator" has always been the common term in terms of mains electricity production.

Wiki says that generator is the blanket term for both AC and DC, with the alternator and dynamo representing the most common generator type for each, respectively.
 

Offline Circlotron

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Re: How did battery chargers rectify AC to DC before solid state diodes?
« Reply #65 on: May 03, 2021, 04:54:51 am »
Nomenclature detail:  strictly, "generators" make DC and "alternators" make AC.
A generator is something that generates something. Its a very generic term. An alternator is merely something that alternates, although in electrical terms we have a fairly clear idea what that means. I don't remember the big generators in power stations being referred to as anything but generators or generating sets.
I'd say there are two types of generators -
Alternators produce AC.
Dynamos produce DC.
Having diodes inside an automotive "alternator" does confuse the issue though.
Then again, an automotive dynamo has an internal mechanical rectifier in the form of a commutator.
 


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