Looking further into this i found that there is a cell chemistry called Lithium Titanate in the marketplace. these batteries can have even higher current ratings than LiPo, they also have a much wider temperature operating range, up to 50C, and down to -30C. They also have 10x the cycle life of LiPo, with LTO batteries a pack would last 20-30,000 cycles.
https://www.alibaba.com/product-detail/ ... 5fefVVxGYE
https://www.ebay.com/itm/Lithium-Titana ... SwgGBbp984
But they have the lower cell voltage, so how can we work around that? The idea to have 6 cells in a module instead of 4 can help with this, running the numbers a 2012 24kwh pack has 96s Lipo max charge volts are 4.0 and the cells is flat at 3.3v that works out to 384 max volts, 360 nominal (@3.75v), and 316v minimum with a total of 65ah. A module made of 6x 55ah LTO pouches in a 3s 2p arrangement would have a max pack volts of 396v (144s*2.75v max charging), nominal of 345v (2.4v nominal) and minimum of 316v and have a capacity of 110ah (36.4KWH and 54-87 years life!!!)
While the 2012 nissan leaf BMS obviously cannot measure two taps inside of each module it could be worked around by putting a high impedance voltage divider across the center LTO cell in each module, that way it would report to the BMS nearly the same “cell voltage” it would expect from a center tap in a 2s LiPo module. But doing that will prevent any balance current coming into the cell. How big of a problem would that be for LTO chemistry?
Also the turtle mode would be activated with some power still left in the LTO pack, but would the BMS have the ability to learn to allow lower voltages before turtle mode kicked in over time? some of these questions can only be answered with experimentation, since its never been tried. sort of like how the BMS learned to allow extra capacity when G2 cells are put into a G1 pack DIY. What about completely fooling the BMS and having an elaborate voltage supply board that scaled the LTO voltages to expected LiPo voltages for any given state of charge at each of the 97 BMS tap locations to allow the LTO pack to go down to its minimum? if the BMS is fooled anyway, then the pack could be made into any arrangement less than the max inverter volts and work with any chemistry! with 100,000+ leafs on the road and near the end of their packs lifes its worth at least talking about it. would this LTO chemistry finally shoot down the main complaint about EVs, that the battery is short lived, expensive and over its life cycle worse for the environment? with a 54 year life, a car would be multi generation, my grandkids could still be cruising around in my leaf in 2072!