Hello. I got about 1000 18650 cells to make one 3.6V/4.2V big cell. I want to fast charge them using either a 12V car battery or other multiple 12V power supplies (in the 300W+ range each). I found these noname Chinese made 40A buck converters CCCV around $13-$25 ea. That means I need ballpark two of these buck converters for each power supply. If I use 5 power supplies, that makes already $125-$250 for the 10 buck converters for a measly 1500W charge capability. If I'm going to have to spend that much just to charge the batteries, I wonder if there is a larger amperage CC buck converters available for charging lithium batteries that might be more economical anyone has run across or give me some pointers. Thank you very much.