It's gotten simpler since that first post now that GC2 form factor batteries are available. But to your comment, this is a one-time thing and is frankly because HiSun went with older technology batteries when it came out.
Now to "fill up" I just plug in to an outlet at the end of the day. No going to the station to fill up cans of gas, no fumes, no noise, no oil changes, no maintenance issues with all the additional little parts that keep a combustion engine going and tuned up, no worry that my UTV sat too long between uses and might not start or the gas needs stabilizer. I can even run electric loads like the light bars I installed without leaving an engine running and worrying about the little 12v battery. I've even considered adding a 2000W 48v dc to ac inverter to run power tools.