What does multiple Batteries Do?

6/4 = 1.5X, or 50% more stored energy.

The additional energy storage could be used for more output or more runtime, or less output with a lot more runtime, or less runtime with a lot more output. How the stored energy is used varies from device to device, even those with the same battery configuration.

On the old fashioned incandescent lights (merely a bulb, switch and battery), adding batteries in series would increase the voltage and hence the brightness (you could keep adding them until you blew the bulb), but adding them in parallel would merely increase the runtime with no effect on brightness as the voltage stays the same.

I think the answer to your question is "It depends". Sometimes manufacturers specify 4 batteries even though 2 would be enough to achieve maximum brightness, and the extra two are purely for better runtime. However 1 battery in the same flashlight wouldn't provide enough power to achieve max brightness, so the second battery is to provide increased lumens.

Thanks to both of you. That clears it up for me. I just bought
a torch that uses 6.

Roy Walker, use black font with stand sized font Colored font can be used occasionally to emphasize information, and to display a color relative to a posting.

Bill