Charging lead acid battery with computer power supply

[Almazick]

I’m trying to charge lead acid battery 7ah with my computer power switching supply. I’ve been using my computer power supply for other project to get 2 amps without putting any load for 5v rail. I raised the voltage in PSU from 12v rail to 13.5v just by adjusting potential meter. I connected PSU to acid lead battery 7ah with amp meter and volt meter. It does look like it charging but only with 150ma and current keeps slowly dropping after I put back into battery 300 mah. I tried to put diode inline but the current dropped to 3ma. What should I do to charge my 12v lead acid battery using directly my PSU 13.5v rail?

 

[RODALCO]

A computer power supply is not really designed to charge accu's.

BTW is this an old one you have laying around , or is it feeding your computer as well ? In the second case you may be overloading your power supply, hence reduced output current.

A charged 12 Volts accu sits at 12.6 Volts with no load connected to it. To charge it properly your charging voltage should be above that. For slow charging opt for about 13.5 to 13.7 Volts, for fast charging max voltage up to 14.4 Volts.

If you supply output is 13.5 volts it should charge your 12 Volts accu.
Put a 12 Volts 21 watt car bulb in series, it will initially reduce your charging current. As the accu voltage builds up the volts drop across the bulb will be minimal, certainly less than a rectifer diode.

 

[Almazick]

A computer power supply is not really designed to charge accu's.

BTW is this an old one you have laying around , or is it feeding your computer as well ? In the second case you may be overloading your power supply, hence reduced output current.

A charged 12 Volts accu sits at 12.6 Volts with no load connected to it. To charge it properly your charging voltage should be above that. For slow charging opt for about 13.5 to 13.7 Volts, for fast charging max voltage up to 14.4 Volts.

If you supply output is 13.5 volts it should charge your 12 Volts accu.
Put a 12 Volts 21 watt car bulb in series, it will initially reduce your charging current. As the accu voltage builds up the volts drop across the bulb will be minimal, certainly less than a rectifer diode.

I'm using a stand alone 500w computer power supply using 13.5v rail output. My lead-acid battery is very discharged and needs to put back around 5A-6A. When I connect directly to a lead-acid battery I get only 120-130ma charging current but if connect the bulb in series would it help?

 

[Cry_Wolf]

Hello Almazick,

I have a PDF, it has a collection of Power Supplies and Charging circuits for probably every Battery type. I think this may be helpful for you and may be for many others. Have a look

**broken link removed**

 

[mashersmasher]

is this a car battery? if so i am very interested in this too.

 

[Almazick]

is this a car battery? if so i am very interested in this too.

It is the same as a car battery but a little bit smaller.