Bruteforce LTO cells for Nissan Leaf battery

[ohilton576]

Hi All,

I am considering doing an LTO upgrade experiment with my old depleted 24kwh leaf battery.
Was looking at the Yinlong 40A cells.

Dala (https://github.com/dalathegreat/Nissan-Leaf-Bruteforce-Upgrade/) recommends against changing cell chemistries for these reasons:-
1. Range estimation/charge bars/GOM:
2. battery management system will not behave correctly:
3. Isolation resistance error:
4. Fast charging issues:

But nothing that seems insurmountable. I would really like to just buy a hundred of these LTO's, bang them in and see what happens.

Assuming that they have similar absorption and discharge characteristics and I can connect them the correct way, and find a micro-BMS solution, and achieve correct voltage range etc. are there any other reasons for not going ahead with this project that are showstoppers?
I mean why aren't LTO batteries mainstream? Is it just a cost thing?

Thanks,

Oliver
(newbie leaf tinkerer)

 

[MikeinPA]

The voltage for the LTO chemistry is at first glance incompatible with the "Lithium Battery Controller" LBC that is in the Leaf battery. The LBC would not allow the car to start or even close the relays inside the battery, because it tracks the voltage of every cell in the battery. The leaf cells cycle from about 4.12 volts to 3.5 volts; the LTOs cycle from 2.5 to 2.0. However, 3 LTO cells in series would cycle in the same voltage range as 2 Leaf cells. If you put 3 LTOs in series, and then placed a voltage divider across that to present 2 voltages, connected the LBC cell monitoring leads to the voltage divider, then the LBC might be fooled into working. The range and other information the LBC is providing would be inaccurate, but that could be lived with. One way to test this would be to take a working pack, and put a voltage divider across 2 of the existing Leaf cells, and then connect the LBC leads to that. If that worked, next try replacing those 2 Leaf cells with 3 LTO cells, and use the same voltage divider. All sort of things could stop this from working. You would lose the cell level monitoring and need a way to get that back which does not irritate the LBC. And finally, you are messing with 400 volts at thousands of short-circuit amps--very dangerous. The LTO cells you would buy are likely not rated for operation at those voltage.

What we need is an LBC configured for LTOs. And a good supply of automotive grade LTOs.