Possible 12V battery charging setup.

Thread Starter

MCH170

Joined May 13, 2021
10
I have a 13.5V power supply and a 12V agm car battery that I need to keep charged up. I thought of this setup to make use of my spare power supply but I want a second opinion before I start using it. The diode has a voltage drop of 0.6V and for the resistor I am thinking of using a 1Ω 25W one. What do you guys think? Thanks for your help.battery setup.jpg
 

crutschow

Joined Mar 14, 2008
30,098
Is the diode to prevent a reverse battery connection?
That will drop the voltage at the trickle charge current (about 50mA for a typical 50AHr auto battery).
So you likely want to increase the supply voltage to about 14V to maintain the battery at about 13.4V.
If you use a Schottky rectifier, the drop will be about 0.3V, so you would bump the supply voltage to about 13.7V.

Is your supply voltage adjustable?
You could adjust it to give a battery voltage of 13.4V after a few days of charging.
More accurate may be to measure the voltage across the 1Ω resistor and adjust the supply to give about a 50-100mV drop (50-100mA charge current).
 
Last edited:

Thread Starter

MCH170

Joined May 13, 2021
10
Is the diode to prevent a reverse battery connection?
That will drop the voltage at the trickle charge current (about 50mA for a typical 50AHr auto battery).
So you likely want to increase the supply voltage to about 14V to maintain the battery at about 13.4V.
If you use a Schottky rectifier, the drop will be about 0.3V, so you would bump the supply voltage to about 13.7V.

Is your supply voltage adjustable?
You could adjust it to give a battery voltage of 13.4V after a few days of charging.
More accurate may be to measure the voltage across the 1Ω resistor and adjust the supply to give about a 50-100mV drop (50-100mA charge current).
Yes, the diode is to prevent reverse voltage.
Yes, the voltage can be adjusted.
I will bump the voltage to 14V as you suggested.
Thanks for your help.
 
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