Trojan has new 12V Group 27 drop-in lithium LiFePO replacement batteries. 4x12V/1400Whr = 48V/5600Whr. You will need a charger that is capable of AGM charging or one that is programmable like Lester Summit 2 1050W or Delta-Q QuiQ 1500. >5000 charge cycles and most likely >8000 charge cycles to 70% of original capacity. These are true zero-maintenance lifetime batteries.
Expensive but maybe worth it to some.
https://www.trojanbattery.com/pdf/da...m_12.8-110.pdf