My recollection from someone far more expert than me was that charging a dead battery, charging a new battery, or charging a BCR at high voltage would burn up the PS 1 board, and that any charging should be done at a lower voltage over a longer time rather than at a higher voltage. This goes back years. There was a guy that specialized in working on ProtoSound 1 systems who had a site up a decade or fifteen years ago; it is my vague recollection that he recommended not using the BCR unless the PS 1 board was modified somehow so that the higher voltage would not burn it up. I believe he said the newer boards designed after the BCR had been out a while was designed to permit their use so it would not cause such issues. I do not pretend to be expert in these matters, but that is my recollection of what someone said who knew a lot more about it than I did, or do!
David