Hi, I use 2 100AH Lithium batteries with our 2019 Sunset Trail 289QB trailer.
Each battery weighs 32 lbs. 100AH A Lead Acid battery weighs around 60 lbs plus range.
Size matches the Group 27 standard.
The only issue to this is the charging. Lead acid battery chargers or the trailer converter can charge Lithium batteries but not to full charge. Lithium batteries have a full charge at 14.3V to 14.6V.
Here is a link to a article explaining this:
https://enerdrive.com.au/2017/11/29/...-acid-charger/
The change I made was adding a Lithium specific battery charger. The 30/45 amp plus models range in price from $30 to $100 plus.
We really like the lithium batteries. They hold their charge when not in use and no messing (in the case of Lead Acid) with water levels etc. No maintenance.
Price is the big issue. A 100AH Group 27 Lithium battery will cost from $900 to $1300 each. Maybe with a sale you could get one for $800.
Weight - Good
Maintenance - Good
Reliability - Good
Charging - Mixed
Price - Bad
Good luck