Let's see if this makes sense. The 5Ah battery does have more capacity, but when it's half discharged, and down to around 36-37V, blipping the throttle on a 25A controller trips the battery. It shuts down, and I have to power off the controller and pedal a bit before the pack comes back. Meanwhile, the 2.6AH battery doesn't do that. It will push 23A and does not pop off. Is it the BMS limiting the current, or less sag in the cells? I don't know, except I have to be more conservative with the 5AH battery. I don't use either as ebike batteries much these days, having moved on to other packs.