im thinking about an 11.1v but i dont know how many mah i need to last the whole day
i know there is up to 2000mAh battery for gel blaster
It would depend on what you have, motor, spring and gear ratio etc. And how much you use it in that day.
I would typically need around 2400 to 3600mah for a full day.
I use 1200mah packs and have 3