Originally Posted by xrated
Your understanding that every battery cycle shortens the life of the battery is absolutely correct....there is no getting around that. But, a lot of the modern LFP batteries are listed at 4000 to 6000 cycles, which is a LOT of years of use, obviously depending on how often you charge and discharge them. 4000 cycles would work out to almost 11 years of battery use, and that would be if you charged/discharged every single day/365 days a year.
A couple of things that do shorten that life is charging all the way to the max voltage of the cells.....3.65V or 14.6V for the battery. I have my charger set to a max output of 14.2V for the battery (3.55V per cell) and so the battery never gets close to the very top end of it's voltage range, yet the battery gets fully 100% charged.....it just takes a bit longer. Same way on the bottom end, the further you stay away from 2.5V per cell or 10V for the battery, the less stress on the battery over time. In most commercially built LFP batteries, the BMS will take the battery off line long before you get that low.
even that is a little bit misleading. if you look at prismatic cells (which are the most popular cell used, aside from the cylindrical that Battleborn uses)
most of them are rated for an approximate life of 3500 cycles. this is defined as a charge from 0 to 100% and drained to 0% again as 1 cycle. So, you can use 100 to 0 as your capacity for 3500 cycles, which for the average weekend warrior is 22 years or something like that. then even at the end of this you will still have a usable battery as cycle life is defined as the point where the battery is reduced to 80% of its original capacity. so, your 100am battery after approx. 3500 full cycles will still work as an 80AH battery.
that 3500 cycle life is not a hard number you can lower it or raise it. The best way to lower it is to leave your battery on a float of 100% all the time or charging it when the battery itself is below 32F or above its high limit.
pretty much all of the batteries sold use a top balancing BMS setup so to ensure they remail balanced you must charge them to 100% once and a while, but aside from this you can pick 90 as your top end and 10% as your bottom, what this does is increase that cycle life. the shallower you keep your discharge the more cycle life you can add.
what I do is charge my 280AH battery to 100% the day before I go camping then I adjust the BMS programing to set the top and bottom hard limits at 10% and 90%. I built my own battery and picked a BMS that allows me to change any settings I want. now do I need to do this, no not really but maybe. I am only 56 so 22 years at 3500 cycles I'll still be camping so I want to see if I can extend that, I'll let you know in 20 years haha. in reality the battery will probably age out before I take out the cycle life.
I did the camper as an experiment. I replaced two 6V GC2 batteries, with 110 usable AH going by the 50% rule, which weighed 160lbs and took up a fair bit of space, with one battery that is approx. 11"long 7" wide and 8" tall and weighs less than 50lbs. This one is using 280AH cells, so I have 2.5 times more usable capacity. it ended up working so well I am now going to build three or four more for my 5th wheel replacing four GC2 batteries so that will take 160 lbs off my hitch weight maybe more depending where I put the new batteries as I want them in a conditioned space, and give me 840 to 1120 usable AH instead of the 220 usable I have now. I could probable get buy easily with two of them, but I want to get close to that 10 days use with the solar not working as I do a lot of camping in early spring and lait fall/early winter and snow is always a concern, so I want that capacity for bad solar days. I do also want to be able to run the bar fridge in the outdoor kitchen and that takes a fair bit of power, but I think this, and a solar upgrade will take care of that easily.