I am solving a problem when charging the battery with MultiPlus 24/1200/25. When charging with low current 7A, the charging is quite standard, but if I increase the current to 12A, for example, the MultiPlus switches from charging mode to inverter mode every 5 - 15 minutes for a few seconds and then back to charging mode. It could be related to the voltage, it already thinks the battery is charged, but I tried increasing the target voltage and I would say it has no effect.
The battery is a LiFePO4 280Ah type. I don’t use any assistants or virtual switch in MultiPlus.
Any idea what this could be?
The battery BMS could be disconnecting charge for some reason such as a high cell voltage. As this only happens at higher current the high voltage cell gets pushed higher. You need to see what your battery cell voltage are. Keep charging at lower current until your battery is balanced. Hopefully you purchased a battery with Bluetooth or other form of comms.
Thank you for your reply. The battery is purchased as a complete unit, the BMS is there Jikong JK-B2A8S20P, so with Bluetooth. But there is nothing wrong in the log via the mobile app. Yesterday I noticed the problem even at lower voltage, 26,8 V. I tried to write to the battery dealer to see if he has any idea.
There is entry in the log with overcharge protection. This indicate one or more cell voltage is over the limit. To check it you need to watch the cell voltage at your battery when it is under charge an almost full.
The other cause is you could have an intermittent ac load on your inverter, something like a fridge starting up. The start up current may be higher than the input current limit to the inverter so it has to stop charging and go into inverting to supply the load. The higher the battery charge current, the less available for ac loads so the more likely that the inverter stops charging.
I must have misunderstood the time stamp in the log dump. I thought it was an event that happened 157 days ago. But it’s probably the total run time. So there are some recent records. I don’t know if the log has a limited capacity because there would have to be dozens of events. I’ll see what the battery manufacturer replies.
It shouldn’t be a jump load on the inverter. Currently the load changes very little in the range of up to 50 watts.
The previous picture was a bad example. That was the time I just turned on the charge.
Here’s an example from yesterday.
Hi again
It looks like your BMS is balancing cells with a to low voltage!
Don’t balance your cells under 3.4V.
You will also need to share all your JK settings.
I have seen mistakes in set up - your log show overcharge protection.
This can be triggered by quite a few settings in the bms.
I found that the log in BMS is probably showing up with the wrong timestamp. The logs are still there and every time I open it, the time changes to the current time. I am still attaching the detailed log from BMS below. It is probably data from the battery factory, as I never had the voltage set that high. The BMS current shows a date of 3/25/2020, and the overcharge information is dated 1/1/2020. But the date may reset with each BMS shutdown (which I did last about 3 months ago). I had the absorption set to 27.4V and the float set to 26.8V.
Cell balance is set to 3.35V from the manufacturer and I can’t change it.
Having found the log to be time old, it rather brings me back to the Multiplus causing the behaviour. I forgot to mention at the beginning that there is still a SmartSolar Charger connected to the battery and when charging from it, I never noticed any problem even with charging current around 30A.
I guess MultiPlus doesn’t have any detailed event log?
I forgot to attach the detailed log from BMS.
Date & Time, System Log, Charge MOS Status, Discharge MOS Status, Balance Status, Heating Status, Max Cell Voltage No, Min Cell Voltage No, Max Cell Voltage, Min Cell Voltage, Battery Voltage, Battery Current, SOC Cap. Remain, SOC Full Charge Cap., Max Temp, Min Temp, Temp MOS, Heat Current
2020-01-01 00:00:03, Boot, CHG OFF, DSG OFF, BALANCE OFF, HEAT OFF, 0, 0, 0.0, 0.0, 0.0, 0.0, 0.0, 40.0, 24, 24, 23, 0.0
2020-01-01 00:00:04, Cell 01 over charge protection, CHG OFF, DSG OFF, BALANCE OFF, HEAT OFF, 0, 0, 3.5, 3.5, 27.7, 0.0, 0.0, 40.0, 24, 24, 23, 0.0
2020-01-01 00:00:45, Cell overcharge protection is released, CHG OFF, DSG OFF, BALANCE ON, HEAT OFF, 4, 5, 3.5, 3.4, 27.6, 0.0, 40.0, 40.0, 24, 24, 23, 0.0
2020-01-01 00:02:16, APP open discharge, CHG OFF, DSG OFF, BALANCE ON, HEAT OFF, 4, 5, 3.5, 3.4, 27.6, 0.0, 239.4, 280.0, 25, 24, 24, 0.0
2020-01-01 00:02:16, APP open charge, CHG OFF, DSG OFF, BALANCE ON, HEAT OFF, 4, 5, 3.5, 3.4, 27.6, 0.0, 239.4, 280.0, 25, 24, 24, 0.0
2020-01-01 00:05:26, Button to turn it off, CHG ON, DSG ON, BALANCE ON, HEAT OFF, 4, 5, 3.5, 3.4, 27.6, 0.0, 239.3, 280.0, 24, 24, 25, 0.0
2020-01-01 00:00:03, Boot, CHG OFF, DSG OFF, BALANCE OFF, HEAT OFF, 0, 0, 0.0, 0.0, 0.0, 0.0, 239.3, 280.0, 19, 19, 19, 0.0
2020-01-01 00:27:30, Cell 01 over charge protection, CHG ON, DSG ON, BALANCE ON, HEAT OFF, 4, 1, 3.6, 3.6, 28.8, 17.2, 280.0, 280.0, 19, 19, 24, 0.0
2020-01-01 00:57:04, Cell overcharge protection is released, CHG ON, DSG ON, BALANCE OFF, HEAT OFF, 3, 2, 3.4, 3.4, 27.3, -7.0, 279.7, 280.0, 19, 19, 22, 0.0
2020-03-14 03:27:39, Button to turn it off, CHG ON, DSG ON, BALANCE OFF, HEAT OFF, 0, 2, 3.3, 3.3, 26.6, 0.0, 267.9, 280.0, 23, 23, 26, 0.0
2020-01-01 00:00:03, Boot, CHG OFF, DSG OFF, BALANCE OFF, HEAT OFF, 0, 0, 0.0, 0.0, 0.0, 0.0, 267.9, 280.0, 23, 23, 26, 0.0
That battery voltage takes quite a dive with such a small discharge current.
What size DC cable do you have? And do you have fusing on it?
What is the volt drop over the cable?
The copper cable from MultiPlus is about 40 cm long, 8 or 10 mm thick. The voltage drop should be very small. I also have a Smart Battery Sense connected to the SmartSolar Charger and it shows exactly the same voltage as the MultiPlus.
I don’t currently have a fuse between the MultiPlus and the battery.
2020-01-01 00:27:30, Cell 01 over charge protection, CHG ON, DSG ON, BALANCE ON, HEAT OFF, 4, 1, 3.6, 3.6, 28.8, 17.2, 280.0, 280.0, 19, 19, 24, 0.0
At this entry your BMS is disconnecting your charge source. Max cell voltage is 3,6V and min cell voltage is 3,6V and your BMS overvoltage protection is 3,6V
If your charge voltage is over 28,8V it will triger a BMS disconnect.
Try lower your charge voltage to 28V.
Just a thought, you are using a lithium charging profile.
As I wrote, the information in the log will be old, probably still from the battery manufacturer, no new entries are added even though the recharging problem repeats several times a day. I normally charge at 27.4V, now only at 27.1V and the problem still occurs. I rather think the fault is in the MultiPlus, since I don’t experience problems when charging via the SmartSolar Charger.
Oh, sory I did’nt pay attention to the date. 
What is the reasoning behind your cell voltage choices?
Set cell voltage in the BMS?
This is set by the battery manufacturer and I have no way to change it.