Hi all
Just a general query to try and improve my understanding of how all of this works.
I have a forced charge set between 2 and 5 am to make use of the cheaper rate electricity.
What I do not understand is why doe the rate at which it imports change? The attached screenshot shows a regular pattern that I am seeing over night.
The first hour is less than 3 kW, then is goes to just under 5 kW and finally down to 4 kW.
My simple question is why is this not a constant amount of kW?
Almost certainly battery temperature at the beginning, as it warms up from charging, it 'unlocks' the next higher rate of charge.
Then as the SoC reaches 9x% then it will throttle the charge power and balance the cells.
Here is an older image showing the cell balancing towards the end.
Then as the SoC reaches 9x% then it will throttle the charge power and balance the cells.
Here is an older image showing the cell balancing towards the end.
It's quite normal behaviour, LFP batteries (their LifePo4 chemistry) have to be carefully managed as they approach fully charged, to do this the charger starts to reduce the charge current usually as it passes 90% soc, but it is temperature dependent as well.
An LFP cell has a very flat voltage across the majority of its charge range but it jumps rapidly as it nears 100%, and also minimum SoC. The BMS manages the charge rate and reduces it to allow time for the individual cells within a battery pack to balance, and for each pack to balance itself with all other packs - this avoids imbalance (in which case you'll see strange jumps in the battery soc as the BMS re-assesses the charge state).
An LFP cell has a very flat voltage across the majority of its charge range but it jumps rapidly as it nears 100%, and also minimum SoC. The BMS manages the charge rate and reduces it to allow time for the individual cells within a battery pack to balance, and for each pack to balance itself with all other packs - this avoids imbalance (in which case you'll see strange jumps in the battery soc as the BMS re-assesses the charge state).