LiFePo4 battery users

[Ticklebelly]

This cannot be done based on voltage...

I suggest you investigate a device known in the RC world as an IMAX B6.   My cells came as nominal 50AH.   Factory test data before release came with the cells I have and all the individual cells factory tested at least a couple of AH above the 50AH.   I played around using the B6 device to establish a usable capacity of 43AH by setting and varying voltage levels top and bottom. 

To aim for a no more than 80% as a goal to get a maximum life out of a battery first requires some decision of what 100% is.    Max life?   what is that?    I will need about 20 years a couple of times before I can report what life I got out of mine.   How will I ever know if I could have got longer life by charging to a lower and upper voltage level?   Three mostly rhetorical questions there.   I am mostly concerned about what usable capacity I have available to run my campervan use.   My EV building friend in mostly concerned with leaving the shop with the batteries as full as electrically possible.   People who have a major focus on battery bank life will need to work out what upper and lower levels to work between. 

I am going to a workshop this weekend to share ideas on good ways to upcycle electrical equipment.   I am building a Li Ion pack to power an electric conversion Quad.   The relevance is that several of the workshop presenters are upcycling lap top battery packs and broken down PowerWall 16850 cells.   Seriously time consuming, but these people are testing individual cells using the B6 to establish either good or bad on the to , be upcycled 18650 cells.   As testing happens, records of the capacity of each cell under test are kept.   Most of the testing relies on looking at the capacity written on the cell then testing the cell to see if the cell gets close to that baseline.