Strangely. Mine, (a Halfords 063?) has been hooked up to a 15W solar panel (Aldi), for the last several years, (yes, I know, I should get back to doing some more on the "kit of parts"😪, but it`s bloody cold in there!!), It is still happily sitting at 12.5V, and occasionally gets pressed into action to start a reluctant "modern"👍. The "file" is very fat, mostly from the P-O`s, back to the 1980`s, I keep threatening to scan it all and archive it. But the paper is impressive, I think it includes the original bill of sale?..
Pete