[emeritus]

I remember that in the late 1950's/early 1960's, the large 3V Ray-O-Vac cycle lamp batteries used to carry a notice saying that any cycle lamp damaged by a leaking battery would be replaced free of charge. These were the metal-clad cells - "Cased in steel" - that I only ever saw sold in cycle shops. My uncle used to use them on his bike, and never had to claim. (My dad's bike had a dynamo, so never used them.)

I must have got through dozens of sets of 6 blue U2 batteries throughout the 1960's to power my EL3585 tape recorder, and never had a single one leak, despite regularly subjecting them to "recharging" by being connected in parallel with a very basic 9V DC mains unit that dad built from a PW article (bell transformer, one silicon diode, one zener, and one electrolytic capacitor). The mains unit's smoothing wasn't up top much, so I tried connecting it in parallel with the batteries and found that, not only was the hum much reduced, but the batteries gave out more voltage after the mains unit was disconnected. Conversely, the early Ever-Ready (white ) "Sealed" U2s did leak, and the early (orange) alkaline HP2 batteries produced too high a voltage for the tape recorder's simple regulator to cope with, so I never used them.