hello,may i ask,what method is the best way to charge a acid lead battery(car battery),

charging voltage usually is slightly higher than the fully charged battery,but if the voltage contain heavy ripple(full wave rectifier WITHOUT capacitor bank),will it shorten the battery lifespan compare to perfect DC voltage?

thanks in advance

 

It depends on the battery and charger. An accurate charger utilizing filtered DC is certainly a good idea, but car batteries get full-wave rectified pulsing DC through an SCR. A car's battery charges in the car without benefit of filtering, too.

We made a very accurate automotive battery charger based on a commercial unit. It kept the full-wave rectifier & SCR, but managed a very accurate float at 13.6 volts. The ripple did not appear to harm the batteries.

 

i was thinking ripple might shorten the car battery lifespan.

can you explain more on your design?why would you need scr?is that you rectify 240v directly and use scr to PWM the output to get average of 13.6v?

i read about slow charging,how would we achieve slow charging?reries resistor does not seem doing the job well unless the resistance is varying accordingly.

 

From what i remember the final charge voltage varies between application. If you're deep discharging it the finish voltage is a little higher. I think this is to help break down the remaining lead sulphate which forms in large quantities during a deep discharge. For float applications like in a UPS or car you don't want the final charge voltage to be too high or you'll electrolyze away the electrolyte.

In general lead acid batteries are extremely robust. The main thing to avoid is deep discharging them, especially a car battery as the plates have to be very thin in order to decrease the internal resistance.

 

The charger I was referring had a step-down transformer. Trying to apply mains voltage is extermely dangerous. There is no isolation for galvanic protection, and the high voltage applied is going to cause excess electrolysis. The evolution of hydrogen and oxxgen gas is a precursor to an explosion. Never try to charge a lead-acid battery with a source capable of causing significant electrolysis in the cells.