How did battery chargers rectify AC to DC before solid state diodes? - Page 1
Forum section: electronics / beginners

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 18, 2021, 03:51:36 pm
content: I know about selenium and mercury rectifiers, but rechargeable batteries have been around a long time. How did people charge batteries from AC without resorting to such expensive rectifiers?

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2021, 04:09:48 pm
content: Did they charge them from AC? There were DC generators and DC power in many places.Early rectification systems included mechanical systems such as a set of contacts driven by a synchronous motor, regeneration system with a DC generator driven by an AC motor and electrochemical systems similar to an electrolytic capacitor except they were meant to break down and conduct, not store charge. All of those were forgotten 15 minutes after silicon power rectifiers became available.

author: geggi1
author_rank: Frequent Contributor
timestamp: April 18, 2021, 04:32:05 pm
content: There where tube diodes back in the day.Selenum rectifiers where first invented in 1876.https://en.wikipedia.org/wiki/Selenium_rectifierMercury rectifierers where first invented at about the same time.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 18, 2021, 04:38:19 pm
content: Quote from: Connecteur on April 18, 2021, 03:51:36 pmThey used these things:-https://www.radiomuseum.org/dsp_multipage_pdf.cfm?pdf=tungar_bulb_data_manual_52410.pdfThey are a mercury rectifier of sorts, but optimised for the simple battery charging job, & hence quite inexpensive.Or they used "Copper-Oxide" rectifiers---these & Selenium rectifiers are hard to tell apart when you get to the larger ones--------they both have large "fins" for heat dissipation.(strictly speaking, they are "solid state")Again, both were used in thousands throughout industry, so prices were not that high.The "Tungar", Copper Oxide, & Selenium rectifiers were quite reliable, if lossy, so in the relatively low stress job done by most chargers, lasted for decades.If you had a large battery bank to charge, a motor-generator could do the conversion.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 18, 2021, 04:45:20 pm
content: Quote from: Connecteur on April 18, 2021, 03:51:36 pmusing 20 cents rectifier ic like this...https://lcsc.com/product-detail/Bridge-Rectifiers_DIOTEC-S380_C212805.htmlwhy bring up or even consider semi conductor from jurassic age?

author: Benta
author_rank: Super Contributor
timestamp: April 18, 2021, 04:49:27 pm
content: Quote from: Mechatrommer on April 18, 2021, 04:45:20 pmUnfriendly and beside the point.If the OP is thinking automotive, dynamos were used for charging. Alternators didn't come into fashion before solid-state rectifiers were available at reasonable price.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: April 18, 2021, 04:56:29 pm
content: Quote from: Mechatrommer on April 18, 2021, 04:45:20 pmTopic title: How did battery chargers rectify AC to DCbefore solid state diodes?

author: Jwillis
author_rank: Super Contributor
timestamp: April 18, 2021, 05:39:42 pm
content: Also you'll want to search Mechanical Regulator .Earlier ones had a cut out (make or break) relay with a voltage regulator . Later ones included a current regulator .

author: coppice
author_rank: Super Contributor
timestamp: April 18, 2021, 06:04:53 pm
content: Quote from: Connecteur on April 18, 2021, 03:51:36 pmSelenium and copper oxide rectifiers, both crude forms of semiconductor diodes, were cheap.They performed poorly compared to modern silicon rectifiers, but they did a perfectly serviceable job in their day.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 18, 2021, 06:19:16 pm
content: Mercury-arc rectifiers:https://www.kemptonsteam.org/history/arc-rectifiers/https://en.wikipedia.org/wiki/Mercury-arc_valveAlso featured in a video game level "Sniper Elite 4 - Magazzeno Facility: Destroy The Mercury Arc Rectifiers":

author: coppice
author_rank: Super Contributor
timestamp: April 18, 2021, 06:36:31 pm
content: Quote from: RoGeorge on April 18, 2021, 06:19:16 pmMercury arc rectifiers were for large scale use, and didn't like being moved around. They were mostly used for high voltages, too. There were small cheap resonant reed rectifiers, which avoided the mercury and the glass envelope, for really crude low voltage use, such as car battery chargers. Even at a low frequency like 50Hz or 60Hz it was difficult to get these things to make and break contact bang on the zero crossings, so the results were kinda nasty.

author: james_s
author_rank: Super Contributor
timestamp: April 18, 2021, 06:45:27 pm
content: Quote from: Mechatrommer on April 18, 2021, 04:45:20 pmDid you even read the question? How is that even remotely helpful?It's like someone asking how Roman chariots were built, and you tell them why even consider an ancient chariot, just go and buy a cheap bicycle

author: ozcar
author_rank: Frequent Contributor
timestamp: April 18, 2021, 08:34:32 pm
content: Quote from: coppice on April 18, 2021, 06:04:53 pmI was a bit surprised to see how selenium rectifiers could be used. If you zoom in to the photo here, you can actually read the labels - "SenTerCel Selenium Rectifiers".https://collection.sciencemuseumgroup.org.uk/objects/co538159/cascade-generator-built-at-the-cavendish-laboratoryI have seen the actual machine on display there in operation, close to 50 years ago.

author: coppice
author_rank: Super Contributor
timestamp: April 18, 2021, 08:53:19 pm
content: Quote from: ozcar on April 18, 2021, 08:34:32 pmLook in lots of electrical products from the 1950s, including battery chargers, and you will find something likehttps://en.wikipedia.org/wiki/Selenium_rectifier#/media/File:Selenium_Rectifier.jpg. Those finned rectifiers were commonplace. Sometimes they were selenium. Sometimes they were copper oxide.

author: ozcar
author_rank: Frequent Contributor
timestamp: April 18, 2021, 10:04:38 pm
content: Quote from: coppice on April 18, 2021, 08:53:19 pmNo fins on the ones I gave a link to. Not sure of the internal construction, but they had to be good for a few hundred kV each.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 18, 2021, 11:08:35 pm
content: Quote from: ozcar on April 18, 2021, 10:04:38 pmI used the term "fins" because it was closer to what a modern person would think upon seeing one.We would have called them "plates" back in the day.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)The large plates were for heat dissipation, as they were lossy devices.Small selenium devices used in radio receivers, etc came in quite different packages, with the "plates" either diminished in size, or missing altogether.The famous "Sentercel" high voltage rectifiers used in some earlier Oscilloscopes were stacked selenium devices.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 18, 2021, 11:21:14 pm
content: An interesting point about Tungar rectifiers:-They could "self protect" against quite severe overloads.I once inadverently shorted the output of the 1930s 6v battery charger I used to charge the battery of my old prewar Chev.I thought I had "killed" it, but the Tungar glowed brightly with the short on, & returned to normal operation when it was removed.A silicon, selenium, or copper oxide rectifier would have been toast!I was having these adventures in the very early 1960s, the car was from 1936, & the charger, a few years older than that!My old work had a very large Tungar charger which was probably of a similar vintage.

author: Renate
author_rank: Super Contributor
timestamp: April 19, 2021, 02:01:08 am
content: Some of the old "vibrators" in old tube car radios did synchronous rectification with extra contacts.The vibrator chopped the 12 V to feed a step up transformer.I think most used a tube rectifier though.

author: Martian Tech
author_rank: Regular Contributor
timestamp: April 19, 2021, 02:37:48 am
content: https://en.wikipedia.org/wiki/Motor%E2%80%93generator

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 19, 2021, 11:32:54 am
content: Quote from: james_s on April 18, 2021, 06:45:27 pmread again the OP.. he asked how to build a roman chariot, without using expensive roman chariot.Quote from: JohnnyMalaria on April 18, 2021, 04:56:29 pmone of the earlier (later?) suggestion is using car alternator... here we go...it should be "helpful"? if we dont consider anything inside the dotted box (before B+) as solid state diodesQuote from: coppice on April 18, 2021, 06:04:53 pmditto!... whats the purpose of placing solid state diodes afterward anyway? if its already rectified to DC? just to drop few multiples of 0.3V? to avoid over voltage trickle charge level?i havent seen that kind of trick recently done by factories... except with my own very crude and unintelligent chargerymmv.

author: coppice
author_rank: Super Contributor
timestamp: April 19, 2021, 01:49:01 pm
content: Quote from: ozcar on April 18, 2021, 10:04:38 pmI think the huge ones you linked to were for pulsed operation. Selenium and copper oxide rectifiers got quite hot in continuous operation, so they were usually mounted on finned heat sink assemblies for good cooling.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 19, 2021, 01:53:04 pm
content: The earliest rectifiers that I know were pools of liquid mercury with a rod hanging over them and with an arc to the pool. Using a large pool they could handle large amounts of current (industrial scale). These were shortly replaced with mercury vapor rectifier tubes and those were still in use into the 1970s. The MV rectifier tubes had a bad reputation because they generated UV-C radiation so they needed to be used in an enclosed cabinet but you can well imagine the hazards of not only the UV-C radiation but the mercury vapor that was added into the room air by mercury pool rectifiers!I used to have a book on the early NYC subway system and, IIRC, it explained the pool rectifiers and had pictures of them. The book 'Electric Circuits and Machines' by B. L. Robertson has a good description of MV rectifier tubes. My copy is dated 1949 but is still useful!

author: Renate
author_rank: Super Contributor
timestamp: April 19, 2021, 02:12:01 pm
content: Quote from: Mechatrommer on April 19, 2021, 11:32:54 amIt's interesting to note that Roman chariots actually used a pair of brushless DC motors.The horses were just for show.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 19, 2021, 02:12:19 pm
content: Quote from: Connecteur on April 18, 2021, 03:51:36 pmBefore the REA (1936) and in the 1920s, 30s and even the 40s, manyruralpeople in the US had their own wind turbines and they put out 36(?) VDC directly. Operating radios and a few electric lights in very rural locations that didn't have commercial power, was a very popular justification for installing a wind turbine. When I lived in rural Virginia in the 1970s these were still in demand! Seehttp://www.jacobswind.net/historyIf you lived in a city that had AC power, other early devices are included AC powered motor driven DC generators. I just saw a NICE one from the 1920s in a surplus store near here. I'll try to get pictures of it if it's still there. Then there were also mercury vapor rectifier tubes if you needed large amounts of power or high voltages. But Selenium, copper oxide and other solid state rectifiers were ahugeimprovement over any of those!

author: coppice
author_rank: Super Contributor
timestamp: April 19, 2021, 02:13:13 pm
content: Quote from: Stray Electron on April 19, 2021, 01:53:04 pmMost mercury rectifiers were of the pool + arc type. They were common in the 1950s, but pretty much gone by the end of 1960s, because silicon rectifiers developed so fast and outclassed them. British Rail introduced trains running from 25kV AC at the beginning of the 1960s, using mercury arc rectifiers in the trains, and they were a disaster. Those rectifiers worked well in fixed locations, but very poorly with the mercury sloshing about on the move. Luckily, silicon rectifiers came to the rescue in the nick of time, and the trains ended up working well.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 19, 2021, 02:14:59 pm
content: Quote from: coppice on April 18, 2021, 06:04:53 pmNails it!

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 19, 2021, 03:08:00 pm
content: What about the vibrating rectifier? The AC causes a relay to invert the inverted power, converting it to DC.

author: coppice
author_rank: Super Contributor
timestamp: April 19, 2021, 03:27:51 pm
content: Quote from: Connecteur on April 19, 2021, 03:08:00 pmI covered that one earlier in this thread.

author: TimFox
author_rank: Super Contributor
timestamp: April 19, 2021, 04:09:22 pm
content: At the other end of the voltage range in years gone by, Shimadzu (the first Japanese x-ray equipment manufacturer) brought a century-old museum piece to their exhibit at RSNA a few years ago that featured a mechanical rectifier to rectify the high-voltage transformer output. A rotating spark gap, driven by a synchronous motor, rectified the voltage applied to the x-ray tube by commutation. Probably wouldn't pass modern EMI regulations.

author: Gyro
author_rank: Super Contributor
timestamp: April 19, 2021, 04:29:52 pm
content: Quote from: coppice on April 19, 2021, 02:13:13 pmUK suburban services (the 600 / 750V 3rd rail ones) used stationary mercury rectifiers for a very long time. Likewise the London Underground train supply.

author: coppice
author_rank: Super Contributor
timestamp: April 19, 2021, 04:45:13 pm
content: Quote from: Gyro on April 19, 2021, 04:29:52 pmYep, the stationary ones work well. I saw some monster ones in industrial applications in the 80s, where they worked well enough there was no point in replacing them with superior silicon rectifiers until they failed.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 19, 2021, 05:23:35 pm
content: Another early non-solidstate rectifier was the Exide Rectifier.https://www.americanradiohistory.com/hd2/IDX-Service-%26-Sales-IDX/Archive-Radio-Retailing-IDX/IDX/20s/Radio-Retailing-1925-02-OCR-Page-0089.pdfOne terminal was lead, the other was aluminum. Add water and a packet of powdered chemicals and it formed a rectifier. I saw a description in a 1930 book about storage batteries.

author: Renate
author_rank: Super Contributor
timestamp: April 19, 2021, 06:30:46 pm
content: Quote from: Gyro on April 19, 2021, 04:29:52 pmNot to get too tangential...I remember the "Green" subway line in Boston in years gone by had lighting int the tunnelsthat consisted of a foot square piece of plywood with five household lightbulbs in an "X" pattern.5 x 120 V = 600 V, AC or DC, it's all the same.

author: BrianHG
author_rank: Super Contributor
timestamp: April 19, 2021, 09:36:38 pm
content: Here is a restoration of a 1920's rare battery charger. Before skipping to the end to see it working, see if you can figure out how it gets DC from the AC source:

author: tooki
author_rank: Super Contributor
timestamp: April 19, 2021, 10:06:27 pm
content: Quote from: Mechatrommer on April 18, 2021, 04:45:20 pmQuote from: Mechatrommer on April 19, 2021, 11:32:54 amUhhh, nope. OP did not ask for advice on how to do it. They asked how it was done in the past.Don’t tell other people to read when you’ve demonstrated your inability and/or unwillingness to do so yourself.

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2021, 10:24:50 pm
content: Quote from: Mechatrommer on April 19, 2021, 11:32:54 amPerhaps there is a linguistic or idiomatic barrier here? Nobody suggested an alternator--I suggested a DC generator--and 'before solid state diodes' in this case means 'in the time preceding the invention of silicon power rectifiers'. It's not a bad question, AC power and rechargeable batteries predate silicon rectifiers by more than 50 years.

author: bdunham7
author_rank: Super Contributor
timestamp: April 19, 2021, 10:26:21 pm
content: Quote from: BrianHG on April 19, 2021, 09:36:38 pmIt uses vibranium! That's an interesting core on that transformer.

author: Robert Smith Eco Warrior
author_rank: Regular Contributor
timestamp: April 19, 2021, 10:32:31 pm
content: I am not that good with history but I think a lot of equipment avoided AC entirely.I have a 1940 Lister generating set that is 3kW 110v DC and was used to power a large house.I also lived in a cottage that was part of an estate belonging to a big house. The big house, not he same one my generator was from, had a room with rows of glass tanks about 2 feet wide, deep and tall and about an inch thick glass. These tanks were big flooded lead acid batteries for powering that big house. The lead had been taken for scrap years before just leaving the big glass tanks.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2021, 10:34:21 pm
content: Quote from: bdunham7 on April 19, 2021, 10:24:50 pmMaybe that's it, that didn't occur to me. In this case "before" clearly means back in an earlier time, prior to the invention of solid state diodes. Not placed before a diode in a circuit. There was a time before silicon diodes existed, and the OP is asking what methods were used back in that time. Totally reasonable question.

author: janoc
author_rank: Super Contributor
timestamp: April 19, 2021, 11:40:55 pm
content: It seems that nobody has posted this here yet:https://en.wikipedia.org/wiki/Rotary_converterThese were pretty common for powering trams, railways, metros and such.Still in operation in 1996:https://www.nycsubway.org/wiki/IRT_Substation_21And a video of it running:And startup with explanation:

author: BrianHG
author_rank: Super Contributor
timestamp: April 20, 2021, 11:39:29 am
content: Quote from: bdunham7 on April 19, 2021, 10:26:21 pmLOL, Literally...

author: coppice
author_rank: Super Contributor
timestamp: April 20, 2021, 07:04:59 pm
content: Quote from: janoc on April 19, 2021, 11:40:55 pmYou could still find mainframe computers in the late 80s running from rotary converters, although most of those were used to convert 50/60Hz AC to 440Hz 3 phase AC, to simplify the power supplies.

author: TimFox
author_rank: Super Contributor
timestamp: April 20, 2021, 07:21:09 pm
content: Nomenclature detail: strictly, "generators" make DC and "alternators" make AC.A motor-generator set has a motor driving a "generator", which strictly means a DC generator. Dynamotors (common field with separate armature windings on a single rotor) were used in WWII military radios to produce high-voltage DC for the plate supply from a low-voltage source (e.g., 200 or 250 VDC from a 28 VDC vehicle battery).A rotary converter has an AC motor driving an "alternator", which generates AC. These are commonly used to change frequency, as in the 400 Hz case above and electrified railways (e.g., the Swiss railways that use 16-2/3 Hz AC, a subharmonic of the 50 Hz commercial mains).

author: bdunham7
author_rank: Super Contributor
timestamp: April 20, 2021, 07:35:58 pm
content: Quote from: TimFox on April 20, 2021, 07:21:09 pm'Alternator' certainly seems to imply AC, at least internally, but 'generator' is a more generic term and the term is widely used that way. It could be generating AC, DC or smoke. Do you have a style guide somewhere that specifies that the term 'generator' can only apply to DC? Perhaps you are thinking of 'dynamo'?

author: TimFox
author_rank: Super Contributor
timestamp: April 20, 2021, 08:52:15 pm
content: 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.

author: coppice
author_rank: Super Contributor
timestamp: April 20, 2021, 09:25:37 pm
content: Quote from: TimFox on April 20, 2021, 07:21:09 pmA 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.

author: bdunham7
author_rank: Super Contributor
timestamp: April 20, 2021, 10:19:46 pm
content: Quote from: TimFox on April 20, 2021, 08:52:15 pmI don't know if Westinghouse used the term to distinguish his generators during the AC/DC wars, but Chrysler used the term in advertising to distinguish their product and it stuck. Years later, the SAE standardized terms and now it is 'officially' referred to as a generator in modern day service and parts manuals. I guess that's the metric equivalent of an alternator. I would point out that all of the devices mentioned so far actually produce AC at their core, the automotive alternator using rectifiers to produce DC while the dynamo is actually a many-phased AC generator that uses mechanical rectification--the commutator. The only mechanical true DC generator I can think of would be a Van de Graaf type.

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2021, 09:45:10 am
content: Quote from: bdunham7 on April 20, 2021, 10:19:46 pmLook up the homopolar generator.https://en.wikipedia.org/wiki/Homopolar_generator

author: Gyro
author_rank: Super Contributor
timestamp: April 21, 2021, 10:38:43 am
content: It's sad that Faraday never thought to try cutting some radial slots in the disc. I remember trying the one in the Science Museum in South Kensington (when you were allowed to do such things). It was a bugger to turn at any significant speed!

author: janoc
author_rank: Super Contributor
timestamp: April 21, 2021, 12:03:13 pm
content: Quote from: TimFox on April 20, 2021, 07:21:09 pmThat's not true. You have plenty of diesel-powered generator sets that generate AC:https://www.survivalcenter.com/Diesel%20Generators.htmlI would even argue that AC generators are way more common because they are simpler and more useful (most appliances meant to run from mains need AC) than DC which would require an inverter.Or even electrically powered sets:https://www.horlick.com/products/motor-generators/Quote from: TimFox on April 20, 2021, 07:21:09 pmThat's not quite true either or rather it is not the only type. Read the articles I have posted and watch the video. They explicitly talk about rotary converters with DC output. That's from New York subway which was converting 25Hz ("cycle") AC to 625VDCused for the third rail.These actually predate the use of the frequency converting types by a lot - the substation with the converter from New York was built and operating roughly 10 years before Switzerland has even adopted that 16 2/3Hz for railways and 2 years before the first line electrified by this type of system (at 16Hz) by Siemens started to operate in Bavaria.Also, rotary converter isnota "motor driving a generator" (i.e. implying two machines connected by some shaft, belt or gears), even though the function principle is the same. The two machines actually share the same armature and field coils, making the whole assembly smaller, lighter and more efficient than having two units connected only mechanically, as is common in motor-generators.

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 21, 2021, 04:22:45 pm
content: 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.

author: janoc
author_rank: Super Contributor
timestamp: April 21, 2021, 04:36:17 pm
content: Quote from: Connecteur on April 21, 2021, 04:22:45 pmYou are assuming that an average consumer in the early 20th century actuallyneededto 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.

author: BrianHG
author_rank: Super Contributor
timestamp: April 21, 2021, 04:50:02 pm
content: Quote from: Connecteur on April 21, 2021, 04:22:45 pmDid 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/#msg3552749A dirt cheap 120v AC in, 6v 5 amp DC charger available in the 1920's.

author: janoc
author_rank: Super Contributor
timestamp: April 21, 2021, 04:52:36 pm
content: Quote from: BrianHG on April 21, 2021, 04:50:02 pmNice old car battery charger.

author: BrianHG
author_rank: Super Contributor
timestamp: April 21, 2021, 04:55:11 pm
content: And it's DC rectifier is powered by Vibranium.

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 21, 2021, 05:23:43 pm
content: 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.

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 21, 2021, 05:26:24 pm
content: Quote from: janoc on April 21, 2021, 04:36:17 pmGood 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.

author: Connecteur
author_rank: Frequent Contributor
timestamp: April 21, 2021, 05:29:13 pm
content: 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

author: james_s
author_rank: Super Contributor
timestamp: April 21, 2021, 06:15:50 pm
content: Quote from: janoc on April 21, 2021, 04:36:17 pmThere 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.

author: janoc
author_rank: Super Contributor
timestamp: April 21, 2021, 06:28:54 pm
content: Quote from: Connecteur on April 21, 2021, 05:29:13 pmLol, andfrom how manywere those 28% calculated?Here is the full quote:"28 percent of all4,192 cars produced in the USin 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.

author: ejeffrey
author_rank: Super Contributor
timestamp: April 21, 2021, 07:40:30 pm
content: Quote from: TimFox on April 20, 2021, 08:52:15 pmThat 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.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 22, 2021, 02:52:48 am
content: Quote from: Connecteur on April 21, 2021, 05:23:43 pmRemember "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.

author: The Electrician
author_rank: Frequent Contributor
timestamp: April 22, 2021, 04:43:03 am
content: Quote from: vk6zgo on April 18, 2021, 11:08:35 pmThis 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.pdfThe 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).

author: vk6zgo
author_rank: Super Contributor
timestamp: April 22, 2021, 06:25:53 am
content: Quote from: The Electrician on April 22, 2021, 04:43:03 amThat 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-GleichrichterThey 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/viewThe 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.

author: tooki
author_rank: Super Contributor
timestamp: May 03, 2021, 04:20:20 am
content: Quote from: TimFox on April 20, 2021, 07:21:09 pmPerhaps 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 thatgeneratoris the blanket term for both AC and DC, with thealternatoranddynamorepresenting the most common generator type for each, respectively.

author: Circlotron
author_rank: Super Contributor
timestamp: May 03, 2021, 04:54:51 am
content: Quote from: coppice on April 20, 2021, 09:25:37 pmI'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.