In article ,
EricP writes:
Before the modern plastic battery weren't they sealed by pouring
bitumen into the top and this could be removed to repair the battery?
Hence the reason for sealed plastic things at large cost.

Prior to around 1940, there were plenty of dismantlable ones
used for valve radios. Any book of that time on radios will
include lots of details on caring for lead acid cells,
including replacing the electrolite, plates, cleaning out
the sludge, etc. Normally you took them back to the shop
for charging and maintenance, but lots of people DIY'ed
it. Actually, we had lots of them at school of the
rectangular glass tank type, where you could lift off the
top with the plates for maintenance. I think they all got
chucked out and replaced with mains power supplies quite
soon after I arrived though.

--
Andrew Gabriel