Hello,

This simple parallel consists of the following materials:
Two bulbs and their own holders
Wires
Eight AA batteries

OK, my goal is to get more amp-hours to prevent unfair bulbs' brightness. I want if I add one more bulb, the brightness of it just the same with the previously bulbs. And the previously bulbs' brightness will not be affected because of adding a new one bulbs.

LOOK AT my schematic

Thank you.

 

If the battery cells are AA alkaline then their voltage is 1.5V or 1.6V when brand new.
You have four in parallel on each side to increase their current or their capacity.
You have both sides in series so their total voltage to the light bulbs is 3.0V or 3.2V.

If you add a third light bulb then the battery cells will run down their voltage sooner because their load current will be higher. When the battery voltage is reduced because it has run down then adding the third light bulb reduces the total voltage and makes the first two light bulbs dim.

 

So, I must just make it four batteries? Two groups of parallel batteries (consisting of 2 batteries) then connected in series???

 

If you want light to last a long time, use white LEDs with the proper resistors. Much longer light output from batteries than from incandescent bulbs.