Note that longevity isn't the only advantage of these batteries:
- round-trip (charge/discharge) efficiency is considerably higher than lead-acid
- less internal/self discharge
These two mean less total energy is drawn from the traction battery to keep the 12V battery charged. This is probably not very significant, but might matter, depending on your priorities.
- maintenance free and spill-proof . . . granted there are AGM alternatives but those aren't 4x less expensive (more like 2x)
- more stable voltage over the discharge curve
- happy to be left at partial/low states of charge, which causes premature aging on lead-acid (even AGM)
- one-third the weight (for comparable capacities)
Frequency of replacement isn't just something to multiply battery cost by . . . for one, that ignores the labor aspect of such a replacement. Admittedly that is small (under four minutes in my video). But risking a dead vehicle due to a 12V battery dying (or just overdischarging) can have a significant cost. With the longer life, less self-discharge, and more stable (higher) voltages of these batteries at lower states of charge, that risk goes way down (in my estimation).
It's been observed that the Nissan Leaf doesn't do a good job of keeping the 12V battery in a high state of charge. This wears out a lead-acid battery more quickly than if it were more fully charged most of the time (due to sulfation). No such worries for a LiFePO4 battery.
Pearl White 2016 Leaf S, 24kWh battery, 6.6kW charger upgrade
Nissan All-Season Floor Protectors
ClipperCreek LCS-25P (NEMA 14-50P)
Ohmmu T12403 LiFePO4 12V Battery