They often use more cells of lower capacity (ie cheaper)Is that your soup in the other bottle or the controller? So 2 for not much more than 2 kilo and my 10amp battery weighs 4.6kg! I wonder why commercial batteries are so much heavier? Better start looking if Aldi still have any bottles left!
But age is amassive factor. High drain 3000mah cells or more simply didn't exist a couple of years ago
Nkon are doing Samsung 30q on a discount. 73 euro delivered for 20 cells (so 36v 6ah)