Originally Posted by _cy_
if self discharge is your most important criteria ... then a sealed battery like AGM will do the job. provided there is no ghost discharge (disconnect battery for long term) a new AGM battery will discharge at 1-2% .. so let's call it 3% self discharge per month. no battery tender needed.
lithium iron phosphate cells discharges at 5-10% per month .... so AGM wins here. note a gel cell battery is best at deep discharge applications. NO battery should discharged to completely dead. permanent damage typically occurs.
AGM and gel cell batteries are similar that both are sealed. they are not the same. Gel batteries should not be charged at over 14v ... permanent damage will occur.
Lithium Iron Phosphate batteries DO NOT discharge at 5-10% per month. Real world experience here. Less than 1% per month static use.