LiFePO4 Battery Lifespan
Lifespan is two numbers, not one: how many cycles the pack survives, and how many years pass while it does. Both are in the datasheet - if you read it properly.
Ask how long a LiFePO4 battery lasts and the honest answer is a formula, not a number: rated cycles at a stated depth of discharge, divided by how often you cycle it - checked against a calendar life of roughly a decade or more. The storage datasheets in this manufacturer's range state the cycle side plainly: 6,000 cycles or more at 80% depth of discharge and 25 degrees C. Cycled once a day, 6,000 cycles is over sixteen years of turns; the calendar side of ageing will usually call time first. Cycled three times a day in a hard-working fleet, the same pack is a five-to-six-year asset. Same battery, different arithmetic.
Depth of discharge is the lever the rating hangs on. A cycle rating is meaningless without its DOD: 6,000 cycles at 80% DOD delivers far more lifetime energy than 6,000 shallow cycles at 30%. This is also where LiFePO4 separates from lead-acid in practice - a lead-acid bank cycled to 80% dies young, so lead systems are planned at 50% DOD, while LiFePO4 is planned at the 80% its rating assumes. When comparing any two batteries, compare cycle count at the same DOD, or you are comparing marketing departments.
Temperature writes the fine print. Heat accelerates every ageing mechanism in a lithium cell; the published ratings assume around 25 degrees C. A pack living in a hot plant room will age faster than the same pack in a ventilated garage, and chronic high state of charge at high temperature is the hardest combination of all. None of this is mysterious - it is why installation environment belongs in a serious quote conversation.
