[biofox]

The batteries were either charged using a "telephone magneto", or were taken to a local town to be charged off of mains electricity:

https://www.1900s.org.uk/1920s60s-windup-phones.htm

[themadturk]

My 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.

[smelendez]

There’s a great radio museum in Howth, Ireland, a waterfront town near Dublin. The founder was a lifelong radio enthusiast who grew up in a poor rural community and was mesmerized by the power of radio from an early age. I remember him telling me he had never heard a language other than English until radio came to town and he heard a broadcast in French. He also talked about using very basic acid batteries and having to go into town to change out the acid. I believe he said it was also a serious problem if you spilled any in the house because it would damage or dissolve anything it came in contact with.

[pyrale]

From what I understand, the crank was used to ring the exchange's bell, not to reload the phone battery.

[greenbit]

Yes, 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.