I am keeping my head down and fingers crossed - 4 years so far on 4 x 110 batteries from advanced batteries, stockport - 2 on the transit side - 1 start, 1 "house", 2 on the leisure side. perhaps Wildebus comment - get more than you need applies !
It really is the case with batteries that that less you stress them the longer they last. And the best way to reduce stress is to fit extra if you have the space to do so
In my own case, because I have changed where I am fitting my new batteries, I have evaluated the space available and am adding an extra one to the install - so getting 3 instead of 2. And with that 50% extra, I fully expect that this
battery bank will last at least the full
battery design life of 15 years.
To do some maths, if I were to add 50% more capacity, but use the same amount of
battery Ahs as before, I would get an additional 1,000 Charge Cycles if I was previously taking it down to 80% DOD.
If I were just taking to down to 50% DOD before (100AH from a 200Ah bank), the extra
battery in the bank would improve the Charge Cycles count from 3,000 to about 5,000 as the DOD you go down to drops to around 33%
And this is just in "normal" use. Factor in High Current
inverter use and the difference between 2-
Battery Banks and 3-
Battery Banks becomes much bigger.
You are in the realm of Lithium Batteries now in terms of usable life
for you (unless you intend to bequeath your batteries to your grandchildren in your will) for a lower price than a single
LiFePO4 battery.
And bear in mind that a 100Ah Lithium for around £650 will deliver a maximum of 100Ah. Your 300Ah Lead Carbon Bank costing £600 will also deliver 100Ah 5,000 times, but will also, if you had the need if "caught short", the ability to deliver 250Ah+ without damaging the batteries (you
will start to reduce the charge cycle count if you do this regulalry, but on occasion, no problems)
Of course, Lithium has other advantages (weight, space, charge speed, etc) and those may well be the deciding factor, depending on individual circumstances.
