SOMETHING DIFFERENT:
Currently, I have set of 3 packs in Parallel with the new JK-PB2A16S20P Hardware V:15
I noticed the other day that 1 pack disabled Charge (it was 100% and BMS stated this even in the "Error Log" Reporting) Other packs were still taking a "tiny bit" yet they were also 100% and cells were "there" voltage wise. I HAD to Investigate of course !
These are 24V/280AH with same BMS. Not currently interconnected (not until I finish the whole bank)
An error is generated because I use only 2 Temp Sensors. Firmware is too stupid to disable the other 2 if in 8S config. (BUG)
The Settings I have that relate to this.
Cell OVP 3.500
VOL Cell Rcv 3.450
SOC 100% 3.449
Cell OVPR 3.448
Simple enough, here's what is happening. I am sending 28.1V (3.512Vpc) to the bank.
BMS sets SOC 100% when the cells reach 3.449
Allows charge to continue until 1 Cell reaches 3.502 and stays there for 60 seconds +/- then turns off charge.
At this point the BMS "LOGS" verbally (into the error log) that the Battery is FULL.
The cells will of course settle a wee bit over time (about 20 mins) to where 1 cell will get below 3.447 and stay there for a bit again and then the charge is turned back on. At which point it tops off and stops again.
I sat & observed 3 packs all go through this cycling process repeatedly and it was all very consistent. Could almost time it to the second.
Unfortunately, the way JK set this up is a bit screwy !
The OVPR must be lower than the SOC 100% and that must be lower than the Cell RCV (part of inverter comms).
NB: All the cells remained below the 0.010V differential.
I tried furtling with the number combos and got the "Data not written" or whatever msg... Really, they ought to put "Value out of Range" or something.
TRICK LEARNED !
I furtled with this for a couple of hours trying to work out how to keep the "cycle" neat as such. Partly because it does take time for the settling and when multiple packs are cycling that that it's "weird" although NOT Harmful in any way. I have ACTIVE Balancing start @ 3.42 and had Balance Trigger Volt 0.010 so I figured try it at 0.005 and "COOL" this actually reduced the cycling and kept the voltages "tight".
Now after I did this I watched very carefully and noted that: The cycling continued for a few minutes BUT after about 15 minutes of that, the cells collectively stayed put and the cycling slowed to maybe once per hour and the cells actually all stayed around 0.003 apart.
With a bit of tweaking on the SCC, this is now working smoother than any previous setups I have done/ tested & beaten upon.
FYI: I do NOT use an AIO. My SCC's are Midnite Solar Classics (no interaction with other gear). I use a Samlex EVO Inverter/Charger (not compatible with JK yet, although I made the introductions between Samlex Engineering & JiKong, never worked out). Maybe because Samlex is Taiwanese ? Who knows.
Bottom Line:
It's important to "know" what the BMS is actually doing independently and how it is logging/reacting to the settings when triggered. For example the BMS setting the SOC state to 100% when it reaches the set SOC-100% Setting Value but NOT triggering the Log Entry that states it is FULL. That "Log Entry" is also the signal sent to an AIO and the only way that gets triggered is when A CELL creeps over the OVP threshold. IMO this is Flawed Logic as cells should never have to reach OVP (whatever it is set to) in order to trigger the "Battery Is Full" msg and send the Stop Charging trigger to an external device.
ADDITIONAL GOTCHA !
As stated, these packs are presently operating "independently" and this is how each is behaving in this situation. With a Master/Slave system as implemented the "Master" pack is BOSS and is responsible for comms to devices. HOW will BOSS react & communicate with several packs in Parallel if not
all have triggered the 100% "Battery is Full". Say 3 of 5 have not set that "trigger" msg. WHAT will happen and how is that handled.
?? F
rom my current understanding of the cycle, BOSS will send the final "Battery is Full" message to Device when "IT" has reached that OVP point regardless of the other packs status. When in reality it should register if ANY pack has not reached that threshold so that Charge Input can continue until All Packs in Parallel have reached 100% Battery Full state with the trigger. The SOC-100% value works for "display" purposes but otherwise not so much,.
Ideally, BOSS should not disable charging input if "any" pack in the bank has not achieved 100% Battery Full Trigger. (Apparently only triggered when A cell within a pack reaches OVP). The BMS' are more than capable of disconnecting charge independently and put the pack into "rest" mode while others can take the rest of the charge incoming. This should be the Default because Banks of Batteries never ever charge "exactly the same" because of numerous factors.
Hope it Helps & Good Luck.
Pinging
@Nami from JK in case they are even remotely paying attention.