Firstly the assumption that a rechargeable battery is 1. 5 v is wrong.
NiCad and NiMH batteries are nominally 1.2 v.
Let's take the latest technology Duracell NiMH battery, 2500 mAh, 1.2 v (measure 1.3v charged). Note I am ignoring cheap Chinese rechargeable AA batteries that claim ridiculous Ah values but using a known brand for my computations.
For 16 Ah battery, which is what yamaha
specify would need 64 AA batteries.
It would cost 3-4 times equivalent lead acid battery and likely to take up much more space, and that is not taking into account the cost and time to connect them together.
Google DIY Lion Car battery - Lion battery technology I believe has the highest power to volume ratio