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.