ian field wrote:
"Peter Dettmann" wrote in message
...

On Fri, 01 Aug 2008 11:58:05 -0400, John Popelish
wrote:


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

The 29 volts is a standard level from a 24 volt battery charger, and
reality they were saying, use a constant current supply. They now
seem to have changed to 1/10 of the amp-hour capacity, and not 1/3 .

Their present recommendation reads:-
Depending on the degree of sulphation, a battery may be recovered
from this condition by constant current charging at a higher voltage
with the current limited to one tenth of the battery capacity for a
maximum of 12 hours.
Note: The applied voltage will exceed the normal recommendation
and so the battery must be monitored (not left unattended) and
removed from charge if excess heat is dissipated. The voltage
required to "force" this maximum current into the battery will reduce
as the battery recovers until normal charging can take place.
In extreme circumstances a battery may never fully recover from
sulphation and must therefore be replaced.

Peter


The book Yuasa sent me many years ago answered just about every question
except the one I'd asked them.

Someone told me that if you soldered to lead battery terminal posts the tin
in the solder migrated through the lead and poisoned the plates, I had been
experimenting with methods of recovering sulphated batteries and often
soldered to the terminal posts - all of the batteries got worse not better,
many equipment manufacturers solder to the spade terminals on SLAs but I
couldn't even find any recommendations on that.


I'd be most surprised if tin could diffuse through lead at normal temperatures in the timescale implied by your remark.