energy dissipation vs cell aging

Still creating the system in my mind, but still the bms part keeps bugging my brain,

let's talk examples here, 14 s system,...

in an ideal world you would balance all cells so all 14 have the exact same capacity, however, with some degrading of the cells, and not each cell being 100% identical (even if you would buy the cells new at once from the same source), so after some times, the cells start drifting apart more and more, the bms (for example batrium) comes into play by balancing the cells so they should all charge up equally.

here are my memory pokes:
- the cells increasing in voltage to fast are basically the bad cells, having fewer capacity, does the bms burn off the FED energy or the allready stored energy? According to my brain itwould make more sense to burn off the newly fed energy untill the "better" cells come into range and only at that pointfeed more "fresh" energy ... and repeat, if it were to burn off the energy allready in the cells you are basically applying more discharge to the weakest links making them weaker?
- in a system for example using the cells between 3.6 and 3.9 would it not be less stressing in the above assumption to let the cells charge (not keeping in mind their neigbors voltage) to 3.9 and then burn off the surplus energy once reached the max and wait for their friends to come to the same voltage?

thanks

1. There is no difference between the energy that is fed to the cells and the stored energy. The BMS turns energy into heat, doesn't matter where the energy comes from. The cells are in series, it is not possible to cut the circuit at the cell that is about to go overvoltage. The energy has to be burnt to keep the cell at its voltage. The only difference would be if this energy is used for something else instead of being wasted as heat.

2. Less stressing than what? Basically you are already describing how a BMS usually works. A BMS turns the excess charge into heat, a balance charger would do the other thing and stop the main charge and continue balancing. These are the two main approaches to balancing. Again, as the cells are in series it is not possible to stop charging a cell and wait for the others to catch up.

1. Yes you can set that in Batrium when you want to burn of excess. During discharge, idle or charging. Its up to you to decide when to balance.
2. Yes Batrium have 2 types of leveling currently active (if you run latest version) The base leveling batrium does is only burn of excess energy of those above set voltage.


So basically you have the excess energy above voltage xxx they will be burnt of. It can also burn of and level cells pending on your settings. Take a look at my video here:

thanks both for your answers, if I watch the video, it seems it bypasses current, since your cells are in series I assume this "bypassed" current is the burned off current?

sorry for my bad and limited english, my worries were towards the balancing act of the "worse" cell, I understood that to balance it, it burned off the energy but to "lower" the voltage it needed to burn off energy from the cell, thus applying a discharge cycle to it, if my understanding is correct, it does not burn off the energy from the cell to get the cell back in line with the others, it just starts feeding it slower (by burning off energy) to "wait" for the others right?

thanks guys

It depends, you can also balance while not charging, which is a discharge then. But you don't have to worry about cycles, it will never be a complete cycle. Far from it actually.

ok thanks guys