Electric Automation Forum
Forum » Power Supply » Charging 12V lead-acid battery and PFC converters
Topics: Charging 12V lead-acid battery and PFC converters on Power Supply
Start by
Alireza Golahmar Zavare
12-16-2013 11:31 PM

Charging 12V lead-acid battery and PFC converters

1- How much current and voltage is appropriate for charging a 12 V lead-acid battery?
2- As you know,in PFC converters,we have output ripple frequency with two times the input frequency.Moreover because of switching we have a ripple high frequency in output.Which one of them is harmful for battery and must be eliminate?
12-17-2013 02:21 AM
Top #2
Mohmd Firzabdi
12-17-2013 02:21 AM
1. Charging voltage is function of temperature, @ 20'C it is 2.25V/cell and @ 30'C increases 3mV equal to 2.28V/cell. This range is useful for battery lifetime.
2. Charging current is a function of Ah rating of the accumulator approx to a half. If the batt. is 12Ah, charge it @ 6A or 2 hours.

You need check the battery manufacturer specification their catalog as well.

3. PFC is @ 65kHz and current spikes on battery should be eliminated by means of proper filter on DC bus. Here you need high quality, high peak current capacitors and some HF inductor as well.
4. Switching frequency is different from PFC frequency. The highest amplitude crest factor should be controlled.
12-17-2013 04:45 AM
Top #3
Kyle Miller
12-17-2013 04:45 AM
It depends on the charger, but I'll break up the questions:
You'll get an output ripple from PFC around 100-120Hz (2x the 50-60Hz line), you can get rid of this with a second stage (and decently fast control loop) if you need to.

Switching frequency that is harmful to lead acid:
Look around for papers from battery manufacturers, but the majority of the papers I've read say any ripple below about 300Hz seems to cause the battery to heat up. So, if you can, try to get rid of the PFC ripple. I would still try to keep you HF ripple around 5-10% of the nominal max DC current as well, but that's not too hard.

12-17-2013 07:34 AM
Top #4
Carole Sherrington
12-17-2013 07:34 AM
It depends on what you mean by "charge".
Telecomm rectifiers, which are essentially switch-mode power supplies designed for battery connection give excellently smooth outputs that are compensated in temperature at between 2mV and 3mV/ cell/degree C dependant upon the battery chemistry and the whim of the customer.
Batteries for use in traction applications that can suffer deep discharges often benefit from 100Hz ripple in the charge current because this promotes localised gassing and recombination at the plates that has a scrubbing action, removing sulphation.
Some batteries require charge current management to prevent localised gassing and distortion of the grid structures. High levels of ripple would be undesireable for these batteries.
It all depends on the battery..............
Reply to Thread