Lithium batteries are taking over GS. Lightweight and very fast charging. You could use a second battery for your solar and locate it closer to the panels.
The GZ lithium 3000 is only 68 pounds! Thats a roll around. I see though lithium batteries cant be paired together like AGM batteries.
I bought Marinco 10/10 chargers for my AGM gels. They work great. 10 amp charge is beyond my solar capability. Maybe if I had a windmill.
By the way battery chargers are designed to have a slow charge rate in the beginning. Its not until it gets to bulk charge that it speeds up. Microprocessor control. You spend the money for the good stuff. Lol