LTO is mature and tested as much as you can with over 10,000 cycle life and >10yr calendar life. The cells I have are currently being used in the more recent BYD busses being sold around the world as the older cells were not as energy dense and did not hold the voltage as high under high current draws (1C to 10C).
I believe that when you calculate the cost per kWh of energy through the battery/cell that LTO works out cheaper, even though the purchase price is higher and this is the reason I waited 2 years for these type of cells to become available outside the vertical companies. I think that these only came into the market because BYD was cought out with the cut in subsidies by China in January for Busses and may not be available in new condition later in the year. BYD and an lot of LTO manufacturers are all verttically integrated and will not sell the cells separately, like Tesla will not sell thier cells separately. All the other BYD cells on the market are 30Ah that have been recovered from older busses, capacity tested and then sold on. Watch for the cells with the small red framed label with hand written capacity value.... they are all used...
A good BMS is an energy balancer and not a voltage balancer. BMS systems typically balance against a nominal voltage at the top or bottom of a charge cycle and do not take into account the "energy" in the cells over the cycle range and this should be balanced closer to mid voltage charge equalisation point and not top or bottom balancing. The top or bottom approach is basically because it is electronically easier to implement, top balancing is just a basic voltage level switch to a dump resistor. Anything other than basic top/bottom you need to computerise and monitor the charge over a number of charge/discharge cycles. Basically you want to have for the worst cell in your pack, to utilise the comparable 10% to 90% capacity of that cell. I fthis means you are using 10% to 80% of another cell and 20% to 90% of another cell that does not really matter, what matteris is you are getting 80% of the worst cell in the mid cycle capacity range to make the most of the cell life..
My own approach is to attach an ESP8266 to each parallel set of cells and use wireles. No wires between cells, each parallel battery set is it's own module and all the data and controll is via wireless. Each ESP8266 is powered via a small DC-DC 1V-5V buck to 3.3V for the ESP. The ESP then controlls a bypass/dump resistor that is switched on for several hours or "days" to energy balance. With this approach there is no need to push and pull the top or bottom of the charge cycle and waste cell throughput. Plus, it works out quite cheap for a BMS... and standby power draw is minimal. I will end up with at least 34 ESP untis for the basic pack and likely around 70 for the two systems (1 fully field portable).
Cell voltage is not really an issue as it just means you have more points for the BMS to manage. Your overall pack voltage of say 48V is the key end result and not the individual cell voltages.. Different chemistry, different voltages. 12V lead acid batteries are after all several sub cells inside the case with no BMS and people did not scream out for a BMS for a 12V lead acid car battery.....
Unfortunately I am not looking to post overseas and would prefer for the buyer(s) to collect as this would provide an opportunity to make sure they know the cells, can test them before buying, I can tell them or teach them any additional information and they can also pick which ones they want so it is very open.
I will possibly end up listing some of them on eB at a higher level to cover eB, PP and post charges, although I would prefer not to waste time and buyers cash on paying 3rd party fees. Hence the post here first. I may end up selling all the cells I have if I can get hold of more, although dealing with China can be quite time consuming and risky.
At the moment the cells are doing around 18kn in the South China sea....