# DC power supply - battery charging [duplicate]

I want to charge Lead acid battery (12V, 55Ah) I have adjustable DC power supply (I can set voltage and limit amps). Do I need to put resistor in between power supply and battery? If so.. how much Ω ?

• With both voltage and current limiting on your power supply, you don't need a resistor. Set the voltage to 14.4 V and the current to less than 20 A and you are good to go. Don't leave it for a long period of time once the current has dropped significatly. – winny Feb 6 '18 at 11:22
• Please do a search for your problem on this Q&A-site before posting questions. The usability of this site and the benefit its users can derive from it strongly depend on not having numerous questions on the very same topic. – Ariser - reinstate Monica Feb 6 '18 at 11:57
• The battery spec sheet (and often, a lable on the battery itself) will specify charge voltage and max current for float and cycle use. Float use uses a lower voltage and current may be unlimited (as the battery will set its own limit at Vfloat. For cyclic use the voltage is higher and Imax will need to be set. See (and bookmark) Battery University for a vast amount of information on batteries - lead acid and other. – Russell McMahon Feb 6 '18 at 12:21

Resistor will not be required, you may limit the current to 1/10th of the battery Ah value, or at the most at 2/10th of the battery Ah value, above this it is strictly not recommended for a lead acid battery. Next, let it charge for 10 to 12 hours minimum, and then remove it from the supply, you will find it optimally charged.

The battery spec sheet (and often, a label on the battery itself) will specify charge voltage and max current for float and cycle use.

• Float use uses a lower voltage and current may be unlimited (as the battery will set its own limit at Vfloat.

• For cyclic use the voltage is higher and Imax will need to be set.

See (and bookmark) Battery University for a vast amount of information on batteries - lead acid and other.