... than to go into discussion with SFK on Andy's YT comment section.
For context, the issue is that the JK (new one) resets its values after x amount of time un-powered. This is a bug, obviously, and the reset values of 4.2V per cell are very bad for LFP. So SFK commented under the video:
Which is not correct. It's not the 4.2V balancing voltage that's the issue. The cell will never see that voltage, because cell over voltage protection for one, and two, during balancing the cell will pull this voltage down (just like with a power supply). So I replied explaining this as well as I could in a YT comment:
To which they replied:
Which completely ignores what I was trying to explain, so I replied:
And of course they missed the point and replied:
Seriously, those guys...
For context, the issue is that the JK (new one) resets its values after x amount of time un-powered. This is a bug, obviously, and the reset values of 4.2V per cell are very bad for LFP. So SFK commented under the video:
The JK BMS (all of them) does Ram/Over Volt Active Balancing where it will send 4.2V to LFP cells to balance them. So I don't think it would have caused the cells to explode at 4.2 it certainly is not good for them. However It would shorten the life of the cells. Please test with a volt meter Andy on any JK device to see the Ram Balancing technique with the JK active balancers, you can simulate the same using a power supply sending 4.2- 4.8 volts for faster cell balancing (not good for the cell)...
Which is not correct. It's not the 4.2V balancing voltage that's the issue. The cell will never see that voltage, because cell over voltage protection for one, and two, during balancing the cell will pull this voltage down (just like with a power supply). So I replied explaining this as well as I could in a YT comment:
A cell that is not at e.g. 3.5V yet will pull down the voltage of the supply (balancer) to its level, even if the supply is set at 10V (constant current mode). If you now have a cell at 3.5V and apply 4.2V to that cell continuously (because your settings are gone) the cell will keep going up in voltage until it reaches 4.2V as well (or before it gives in before getting there). So for a balancer, it's not an issue since the cell itself won't get to a value over 3.5V (if that's where the cell high voltage disconnect is) even if the balancer voltage is 4.2V. If however the cell protection sits at 4.2V after a reset, the cell will get to 4.2V, and likely vent/bloat (charger settings ignored in this discussion of course, but after a reset, it could request the higher voltage from the charge controller if comms are set up).
To which they replied:
This is absolutely incorrect, incoming voltage should never exceed 3.65v on LFP cells, doing so will damage the cell. LFP cells must be charged using the CC/CV constant current / constant voltage method meaning once they reach a fully charged voltage of 3.65 volts only the incoming amps should be adjusted as needed as to maintain this voltage. Over-volting a cell to speed up balancing is harming the cell because the cell is forced to absorb amps higher than it would do under normal charging circumstances.This is why the JK is able to do constant 2 amp balancing because it Ram Balancing / Over-volt balancing.The capacitor style balancing is far better for the cell, it is slower but safer way of balancing cells as the cell never sees an input voltage greater than 3.65.
Which completely ignores what I was trying to explain, so I replied:
Take a e.g. 10A lab power supply, take an LFP cell at 3.1V. Put the lab supply at 4V before connecting. Connect to the cell. What does a multimeter show as a voltage at the cell?
And of course they missed the point and replied:
Why stop at 4v why not put 8v, how about 10v? It is truly remarkable how uninformed you are, I guess now we have to make video explaining why this is bad.
Seriously, those guys...