question

Hi @Owenski There are lots information out there and even on the forum so I am not going to repeat anything. It is really something that should have already been taken care of during the requirements definition and system design phases.

One key aspect is how will you be using your system? Daily consumption or backup only. That could be the deciding factor.

Personally Lithium is the way to go if you can as it charges more efficiently, has smaller footprint for same size e.g. LA, safer, many are "self managed" with own BMSs etc. etc. To oversimplify it, imagine replacing your phone battery with agm, la or gel equivalents.

Only thing to be mindful of is low temperatures as Lithium does not like being charged below 5 degrees c. Not sure about the 7 year lifespan as often lithium is even guaranteed to still have 70-80% usable capacity after 10 years if used as per the manufacturers specification. My NCM 189Ah is discharged every day down to about 10% during winter (i dont have solar) and can be charged fully to 98% (inbuilt limit) in 4 hrs at 40A.