why i call Li fussy
Hi all, This doesn't cover all the concerns for me, but it does show at least some of them: https://youtu.be/_PgthByAYz4
Forum Discussion
It certainly seems to me (and probably others) that there is a whole lot of picking going on. To paraphrase, the question is never 'how does this work?' but 'looks like it won't work between 0 - 5c', 'looks like it won't work with an inverter/charger'. Then there is the 'it would be impossible to heat the battery because I made up some numbers', 'let me come up with some sort of crazy scenario where that might not work' etc. The whole point of this thread seems to be to pick at something without any real understanding or experience with how it works.
As to the 'BMS disconnects the cells', as you suggest, the writer of that really does not understand how their solid state BMS works. The battery will continue to allow the battery to discharge below 0C so clearly it cannot have 'disconnected the cells'.
As I think I have explained several times before, the BMS acts like a programmable ideal diode. For most of the time, when the temperature/voltage/current is within spec it is in bidirectional mode and will let current flow in either direction (ie it looks like a wire). When it is in charge cut off mode, either because the temperature is too low, or the voltage is too high etc, it will only allow current to flow out of the battery. When it is in discharge cutoff mode, because the battery is depleted, it will only allow current to flow into the battery. It will never be in both charge and discharge cut off mode.
A heated battery at low temperature is in charge cut off mode - it won't allow current into the battery, but turns on a heater upstream of the BMS 'diode' so that current can flow to the heater. To the charger it looks like any other LiFePO4 battery.
I am happy to explain how this stuff works and clear up some of the many misconceptions, but it would be nice if this wasn't always an argument.
As to the 'BMS disconnects the cells', as you suggest, the writer of that really does not understand how their solid state BMS works. The battery will continue to allow the battery to discharge below 0C so clearly it cannot have 'disconnected the cells'.
As I think I have explained several times before, the BMS acts like a programmable ideal diode. For most of the time, when the temperature/voltage/current is within spec it is in bidirectional mode and will let current flow in either direction (ie it looks like a wire). When it is in charge cut off mode, either because the temperature is too low, or the voltage is too high etc, it will only allow current to flow out of the battery. When it is in discharge cutoff mode, because the battery is depleted, it will only allow current to flow into the battery. It will never be in both charge and discharge cut off mode.
A heated battery at low temperature is in charge cut off mode - it won't allow current into the battery, but turns on a heater upstream of the BMS 'diode' so that current can flow to the heater. To the charger it looks like any other LiFePO4 battery.
I am happy to explain how this stuff works and clear up some of the many misconceptions, but it would be nice if this wasn't always an argument.
