My grandmother from rural Saskatchewan said that back then they would exchange their radio batteries when they went to town.
replyHer husband, my grandfather, lived in Regina but worked on a traveling threshing crew and mentioned seeing a windmill driving an old generator from a car to charge batteries at one stop.
The batteries were either charged using a "telephone magneto", or were taken to a local town to be charged off of mains electricity:
replyMy father in law grew up in the Denver area. His father made his living as a handyman, and one of his regular customers was Molly Brown (the Titanic survivor known as "The Unsinkable Molly Brown"). Every week he would go to her house to exchange her radio battery, then bring the old battery back to his workshop for charging.
replyFrom what I understand, the crank was used to ring the exchange's bell, not to reload the phone battery.
replyYes, in the old systems, you'd get about 90 volts AC down the line to ring the mechanical bell ringer. Once saw a guy nearly fall off a ladder, splicing phone lines with bare hands. He thought the relatively low voltage was safe enough, but then someone rang him in the middle of the job.
replyI know 30+ years ago as I kid I learned this in my parents basement as I was rigging something up.
replyIt is more the surprise, as if one is ignorant to this fact it is not expected at all.
The phone batteries weren't a high load kind of affair. They merely needed to change the varying resistance of the carbon microphone into an audio voltage - on the order of milliwatts of power - to send down the line. A more modern phone, still using a carbon microphone but powered by the line, needed about 20mA of loop current to do this. The telephone terms for the old system vs. the newer is "local" vs. "common" battery.
replyHeavy duty batteries - specifically the "A" batteries that powered the vacuum tube heaters in early radios - were made rechargeable to save cost.
This might be a bit of a tangent but I couldn't help but wonder if the appearance of 20ma here is related to the old fashioned, but I understand commonly used, 4-20ma current loop signalling in industrial applications.
replyIt's almost never a coincidence. Before digital switching everything was done mechanically, and before mechanical switching everything was done by people with plugs. If you have a big enough industry like telephone switching equipment then you're bound to see a lot of suppliers expand their market by selling the same parts outside of their home industry. Current flow is a nice signalling mechanism because you can tell the difference between short, open, and functional circuit. So I'm guessing it got used in telephone switching equipment and then preserved because there was no reason to change.
reply> Sadly, he did not say how the batteries were re-charged.
replyDry-cell batteries had to be changed, they weren't recharged.
https://www.reddit.com/r/diyelectronics/comments/y7qmhq/15v_...
If the batteries were rechargeable at all (some radio 'A' batteries [0] were), they could have been recharged by a small wind turbine [1].
replyMaybe they used a Delco-Light Plant
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