Those batteries.
Am i misunderstanding but you can get 48v (51,2 volt packages) at 100 ah for 1.500 usd. That would be cheaper :)
https://shop.signaturesolar.us/products/48v-100ah-lifepower4-battery-by-eg4?ref=cPwLcVc0SW-BjN
good luck, lets know how it goes