SOK 48v: draining extremely quickly

[Aussieguy]

swap 2 and 5............ so they become 3 and 4
double check all battery connections and wires
heat gun of feel connections to check if any are getting hot

Investigate whether a bus bar would be better (if you don't already have bus bar connection between batteries)

 

[dothedr3w]

Ok I've been monitoring and allowing the cells to balance since my last post. Here are the numbers:

11 Feb 2023

#1 PackV: 56.09v
#2 PackV: 53.91v
#3 PackV: 56.09v
#4 PackV: 56.12v
#5 PackV: 56.11v


Pack 1 Cells:
1: 3507
2: 3508
3: 3506
4: 3508
5: 3505
6: 3509
7: 3508
8: 3508
9: 3508
10: 3508
11: 3492
12: 3508

Pack 2 Cells:
1: 3338
2: 3361
3: 3345
4: 3357
5: 3421
6: 3346
7: 3360
8: 3360
9: 3337
10: 3416
11: 3366
12: 3352

Pack 3 Cells:
1: 3512
2: 3513
3: 3512
4: 3512
5: 3397
6: 3510
7: 3507
8: 3515
9: 3519
10: 3512
11: 3512
12: 3513

Pack 4 Cells:
1: 3512
2: 3512
3: 3495
4: 3512
5: 3497
6: 3511
7: 3513
8: 3514
9: 3506
10: 3507
11: 3490
12: 3512

Pack 5 Cells:
1: 3508
2: 3509
3: 3408
4: 3506
5: 3509
6: 3509
7: 3509
8: 3507
9: 3507
10: 3489
11: 3509
12: 3509

Summary of cell below 3.5v:
- Pack 1 Cell 11
- Pack 2 (all cells)
- Pack 3 Cell 5
- Pack 4 Cells 3/5/11
- Pack 5 Cells 3/10

 

[Lt.Dan]

Pack 2 cells are all low, and most below 3.4v. Can you check "BMS Status:" and see why its not charging to a higher voltage?

 

[dothedr3w]

Pack 2 cells are all low, and most below 3.4v. Can you check "BMS Status:" and see why its not charging to a higher voltage?

I will try this and report back

 

[dothedr3w]

Pack 2 cells are all low, and most below 3.4v. Can you check "BMS Status:" and see why its not charging to a higher voltage?

Should I worry about the cells between 3.4-3.5v in the other batteries if the PackV is acceptable?

 

[Lt.Dan]

Should I worry about the cells between 3.4-3.5v in the other batteries if the PackV is acceptable?

Pack 3, cell 5 is a little low, but not terrible. It's really close.

Pack 5, cell 3 is the same, but not terrible.

Pack 2 is the only concerning one, need to find out why it's not charging to a higher voltage.

 

[JRH]

There is common debate for float as well. I personally do not float. So I set my Bulk/Absorb/Float all to the same voltage. The argument is if you Absorb to 56-57v (roughly 3.5v), then immediately drop to 54.4v (3.4v), then you are still not allowing much (if any) balancing to happen. I like to bring my cells up to 3.5v, then hold it there, and give the balancers enough time to balance properly, where there is no confusion if a cell is actually at 100% or not. This argument is moot though, if the BMS will only balance while charging, which quite a few BMS's do.

I tend to do closely what you are doing. “ push them doggies” .. since I started 6 months ago pushing them rather than pampering them they do excellent ..always balenced and ready to roll .
When I was trying to baby them they drifted all over the place all the time… baffling …..

Now I use a Very high charge and sit awhile ….very low charge and then reverse ….always in balence at any point in the full cycle …also excellent load sharing #’s….
Like a good pack of hunting dogs , they are in shape to run…

If they die a little bit early , then so be it…at least while they were here they did their job without causing me grief..
J.

 

[marionw]

BMS Closed loop is probably managing the charge voltage thus the charge current and BMS communications will override any default bulk/boost and float charge voltage settings. The Master BMS is probably happy with the state of all the batteries so charging is conservative.
I am not familiar with your specific (SolArk 15k) inverter but generally if you simply disconnect the BMS to Inverter communication cable the Inverter will default back to whatever manual settings you have set for "Max" bulk/boost and float charge voltages as well as "Max" charge current. You should get a BMS Communication Fault but if it does not shut down the inverter it OK as you know why you have the alarm.

If you look at the "Parameter Settings" tab in the SOKTools you will see that the BMS setting for "Balance Threshold(V)" is 3.50. In addition you will see that "Cell OV Alarm(V)" is 3.60 and "Cell OV Protect(V)" is 3.70. "Pack OV Alarm(V)" is 57.60 volts. If a cell hits the "Cell OV Protect(V)" the BMS should open the Charging MOSFETS to stop all battery charging. You ideally want to get the "some" cells to Balance 3.50 volts at which time the BMS will start to passively balance them by using a bleed resistor to use their voltage to help charge the other cells.

What you want to do is have a charge voltage (try 55.5 to 56 as a start) that will get the some of cells to the "Balance Threshold(V)" of 3.50 volts and not exceed the "Cell OV Protect(V)" of 3.70 volts.

You certainly can charge at a greater voltage but you must monitor the other batteries as they are also being charged. You will by trial and error find the "sweet spot" so that periodically you disconnect the BMS Communication cable to fully top off the batteries.

 

[dothedr3w]

BMS Closed loop is probably managing the charge voltage thus the charge current and BMS communications will override any default bulk/boost and float charge voltage settings. The Master BMS is probably happy with the state of all the batteries so charging is conservative.
I am not familiar with your specific (SolArk 15k) inverter but generally if you simply disconnect the BMS to Inverter communication cable the Inverter will default back to whatever manual settings you have set for "Max" bulk/boost and float charge voltages as well as "Max" charge current. You should get a BMS Communication Fault but if it does not shut down the inverter it OK as you know why you have the alarm.

If you look at the "Parameter Settings" tab in the SOKTools you will see that the BMS setting for "Balance Threshold(V)" is 3.50. In addition you will see that "Cell OV Alarm(V)" is 3.60 and "Cell OV Protect(V)" is 3.70. "Pack OV Alarm(V)" is 57.60 volts. If a cell hits the "Cell OV Protect(V)" the BMS should open the Charging MOSFETS to stop all battery charging. You ideally want to get the "some" cells to Balance 3.50 volts at which time the BMS will start to passively balance them by using a bleed resistor to use their voltage to help charge the other cells.

What you want to do is have a charge voltage (try 55.5 to 56 as a start) that will get the some of cells to the "Balance Threshold(V)" of 3.50 volts and not exceed the "Cell OV Protect(V)" of 3.70 volts.

You certainly can charge at a greater voltage but you must monitor the other batteries as they are also being charged. You will by trial and error find the "sweet spot" so that periodically you disconnect the BMS Communication cable to fully top off the batteries.

I'm trying to convert this to my lamenst terms....just disconnect BMS and watch?

 

[dothedr3w]

I'm trying to convert this to my lamenst terms....just disconnect BMS and watch?

Oh should I just 'take all batteries out of the system's by turning them off and disconnecting the BMS comms cable? And make the shitty battery 1 of 1 battery known to the inverter?

 

[marionw]

Yes, unplug the BMS communication cable at the battery or the inverter, but check whatever you have set for battery charging parameters in the inverter software. You should hopefully see the values change when you disconnect then re-connect the BMS Communication cable (may have to change or refresh the screen).

Monitor all batteries with the SOKTool. If you select "FF" for the "Pack" in the "Serial Port" box you will be able to monitor all connected batteries

 

[dothedr3w]

BMS Statuses:

Pack 1: Full
Pack 2: OVP
Pack 3: Full
Pack 4: Full
Pack 5: Full

I've turned off all batteries except #2. Disconnected all communication cables.

Float/Absorption/Equalization voltages are all set to 57.6v, and the battery is currently reading at 53.2v on the inverter. If I plug the comms cable directly back into the OVP battery, and only that battery, it reads as 99%.

How can I get the battery out of overvolt protection?

 

[dothedr3w]

Update: with the comms cable attached it's registering OV (overvolt) as 'Yes', but its status isn't OVP anymore status is now 'idle'

 

[dothedr3w]

Update again:

With the closed loop system completely disconnected, the BMS status is now 'DSG'.

I'm assuming that means discharging. The inverter has stopped using grid power, and is actively draining the battery at about 2.2kW

 

[dothedr3w]

Well I think the BMS is toast on that battery. Everything was trending positively when I went to bed last night, but when I woke up, it was stuck at 53.9v and had kicked back into OVP.

 

[Lt.Dan]

Well I think the BMS is toast on that battery. Everything was trending positively when I went to bed last night, but when I woke up, it was stuck at 53.9v and had kicked back into OVP.

It could have 1 cell running, and kicking on OVP, then by the time you look at it hours later, the cell has settled down to a more reasonable voltage.

You need to catch it in the act

 

[Rich V]

@HighTechLab
Ask the expert

 

[marionw]

You need to ensure all batteries are FULLY charged. Just because the BMS indicates a 100% SOC does not mean the battery(ies) are FULLY charged. Until you get the battery(ies) FULLY charged the BMS has no idea what 100% SOC truly is. The cells are probably extremely unbalanced.
Once you get the batteries to 90%-95% SOC and the charge source is able to deliver at least 56.2 volts (Pack OV Alarm is 57.6) and 5 to 10 amps per battery (per battery means the charge source needs to deliver 5 amps * battery count). When cell(s) reaches 3.5 volts which is the Balance Threshold (for an SOK Battery) you will see the BMS start to passively balance the cell(s) by engaging a bleed resistor for that cell(s) to use its extra voltage to charge other lower voltage cells and to limit it's continued charging. Hold this charge for some time and you will see the battery charge amps slowly decrease as the battery voltage slowly increases. Once the charge amps are less than 1 amp (preferably 0) the BMS will now know what 100% SOC really is and the battery(ies) will be FULLY charged. This process is a must for any new battery being added into a solar system.

 

[HighTechLab]

The others in this thread pretty much summed it all up. Charge your batteries to 100% whenever possible and try to stop draining at 20% if you want to be "nice"...but lower is still fine. They like to be treated rough and cycled often. Run with comms if possible and things will work themselves out after a few cycles. The BMS will keep everything under control, physically limiting or stopping charging as needed for balancing.