ian field wrote:

Yuasa publish a "Little red battery book" which recommends supplying a
sulphated battery with 29V current limited to 1/3 of the Ah capacity,
assuming the sulphation starts to break down the terminal voltage will pull
down to the deep discharge value ( about 10.8V for a 12V battery) A
comparator should be arranged to detect this event and switch the charger
over to constant voltage charging (about 13.8 to 14.4V).

Down loadable in PDF form at:
http://www.yuasa-battery.co.uk/indus...downloads.html

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Regards,

John Popelish