Thanks for the feedback guys
I've killed a few car batteries in the past too (not braille), but it was probably my fault. Battery would typically go flat from lack of use. After doing this more than a few times, they just died. Did some research and learned about sulphation and how it damages the cells.
I think
AGM batteries like braille and deka discharge pretty slow normally (<3% a month?). But I found my Brant/Subaru alarm (or something else?) would fully drain a big battery in a week or two, and a race battery even faster. Then most chargers just wouldn't charge them.
The lesson for me... an automatic charger with race connections is cheap insurance.