I’m not sure that I understand your units here: “1’9-3fv?” The best batteries to use are usually AA or AAA cells, as they have good energy density. But, 4 LEDs in a string can use 12 V or more to run at full current, depending on the colors and how bright you want to run them. It may be better to run from 4.5 V (three AA or AAA cells), so as to minimize battery size and weight, but then to run the LEDs in parallel, each with their own resistor.
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