Hi Community,
I ran a MP II 48/5000 with a 48V/280Ah (EVE LiFePo, 16S, self-built) battery using a JK BMS.
The discharge process stops at 52V, which is around 30% SoC, but I'd like to go down to 3,0...3,1V cell voltage, means a cut-off voltage of 48..49,6.
As far as I understand the discharge limit is defined by the SoC (I usually set it to 20%, which I never reach) and the Dynamic cut-off voltage, right?
Where can I change the Dynamic cut-off voltage?
Thanks in advance for your support,
Oliver
I suspect you're confusing different things and you haven't detailed enough about your config so we can only rattle off obvious stuff.
If your system is controlled by the BMS, the BMS will tell the system when to stop discharging by dropping the DCL, this can be checked via VRM widgets.
If this is the issue you need to tweak your bms.
Voltage and SOC in a lithium battery have a vague relationship, you can't use one to determine the other.
DIY cells can vary in quality, one cell dropping under load is not uncommon and makes interesting things happen for the BMS and broader system, this can also be seen via VRM widgets.
If you are using ESS, then you need to drop that minimum SOC, remembering it is overridden by batterylife active SOC.
There are also cutoffs set in the inverter tab of the multi, if enabled, both voltage and SOC.
The ESS assistant has it's own cutoff and sustain settings which must be set for your battery.
All pretty thoroughly documented in the relevant manuals and guides, and often already asked and searchable on the community.
My JK BMS is configured to only control the max/min limits of all relevant battery related parameters, which I have never reached so far.
I control all charge/discharge processes and parameters via Modbus and have far more parameters on display, than the VRM widgets do offer. So I also have a clear view on each individual cell voltage and potential drifting of cells.
My ESS has the following settings,
but somewhere there is a discharge cut-off at app. 51.2V...52V defined and I could not figure out yet (even reading through the manuals and the forum) where this limit is being configured.
I'd very much appreciate a hint, where to find the parameter defining this cut-off voltage.
In case someone has the same problem, here is the solution (thank you Jörg of meintechblog.de):
Open VE Configure -> Tab "Assistants" -> Select Assistant "ESS..." -> Start Assistant -> Click ">>" until you get to the "Dynamic cut-off" page and there change the settings accordingly:
As an example in my case (16S 3,2V LiFePo) I chose 48,00V for all discharge current fields, as I control most of the process externally and use the assistant only as backup in case my controls don't work.
