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Recharging a car battery Answered


My burning question is if I can recharge a car battery with a 12 v 5 Amps DC energy source. The car battery is a 12v 70 A standard battery, i think it uses Lead. I am asking because i do not have any experience in recharging car batteries and i know that mobile phone batteries can explode if you do somenthing wrong, so i want to get it right the first time with a car battery. Thanks.


If the output of the charger is greater then the battery then you should be fine.

What is the power source your using. If its a charger of any kind it should have protection diodes of its own.

When connecting the power source to the battery you'll want positive to positive and ground to ground.

It is not an ordinarry charger. It`s a custom power supply wich a friend made for a car subwoofer amplifier. It connects to 220 and right now it gives about 12.1 volts. But it has a a button inside wich i can rotate to modify the output voltage. I did a little research and found out that the flow is determined by the diffrence between the 2 power supplys. Va-Vb= power flow. So in my case 13.5-12.4=1.1 so current is going in my battery not the other way arround. But i will check from time to ime if the ratio is beeing kept. Thank you verry much for your help.

FYI, while the output is 13.5V that is without a load. When you put a load on it such as connecting it to the battery there will be a voltage drop. If the PSU isn't well regulated the drop may put you below 12.4V. So its best if you go out and get the right Diode to prevent any issues.

It think it is regullated because when the subwoofer was making a continuous deep bass at its maximum power it had a fraction of a second at the begining of the test where the light on the amplifier would go dim and the sound got a little distorted, but after that it works perfectly. I guess that is what you ment by regullated. But better go and get my friend to put those diodes in just to be safe. Once again many thanks.

Lead acid car batteries are very resilient. There is a wolrd of difference between them and a cell phone battery. They can take 15V or more for charging without a problem. Even a little 12V solar panel that push out very low amperage will charge the battery. Most commercial chargers output 12v @ 5A or more.

Just be sure whatever your source is that it has protection diodes in place. You want the power flowing from your charger to the battery not the other way around. Just keep in mind the lower the amperage going in the longer it will take to charge the battery.

Thanks for your answear. I checked and i don`t have those diodes so i can not use it right now. Another quick question. I can raise the voltage in that power supply to about 13.3-13.5 V . The measured voltage of the car battery is 12.4. In this case the flow of electricity is still a problem? Or how can i verify wich way the energy is going?