12v sla charger

[asimov_18]

hi folks,
i am constructing a small ckt for 12v sla(ups battery) battery charging with automatic cut off . the problem that comes up is that generally a charged battery should have a voltage around 13.8 volts.
but while charging the battery voltage varies considerably when connected to a 12v mains transformer through a rectifier becase the voltage from transfomer is around 15 volts . secondly if u disconnet a freshly charged battery the voltage is much above 13.8 volts . so how does one know wether the battery is fully charged or not.
any comments or suggestions
asimov

[docel]

1. You need to look upp the manufacturers Data sheet for the batteries.
2. Open circuit voltage is 13.8, will coast down to 12.6 to 12.8 after cooling.
3. Any lead acid battery will clamp the source to 14.45V. This si also the max charge voltage.
4. set for 13.9V charging .This will draw minimum current when fully charged (float charge)

5.You should not 'design' anything unless you follow the manufacturers data sheet and the respective parameters.!!

6. No need to 'design': its already there. You can probably improve existing designs for something better.

[asimov_18]

sorry folks for miss framing my sentence