UK Using 3 Fogstar 5.12kWh Energy Server Rack Batteries, cant keep them in sync

[Oldman2]

Balance threshold is too high, try 3.4v and I personally go with 15mv differential.
Seems like you may have a cell in that 1 battery that is not so great and it limits the charge that battery can absorb.

I have now altered the Balance threshold to 3.40V on each of my battery BMS's but 15mV balance is below the available limit set, I have to use 20mV as that's the lowest available to me.
I now have to wait at least until tomorrow for any chance of enough PV to fully charge the batteries, dull & raining with 18watts so far today.

Using battery 1 & 3 since yesterday as suggested @DIYrich Start numbers were:
B1 54.80v 100% 99780mAH remain 99780mAH full capacity
B3 54.84v 100% 99740mAH remain 99740mAH full capacity

By this morning after a night of discharge but including 2kWh cheap rate grid charge.
B1 53.18v 77% 76930mAH remain 99760mAH full capacity
B3 53.15v 76% 75350mAH remain 99740mAH full capacity

So already there is 1340mAH difference in the remaining capacity between these 2 batteries in just a few hours.

 

[ABJ]

I wouldn't worry about it.
I've got 3 SOK 5.1KWh, they have the same Pace BMS. When they charge fully they suddenly jump to 100%, it's the BMS not recording the correct SOC.
I have the same configuration of leads as you do.

 

[goldserve]

If you have cell level monitoring, all I care is that all my batteries make it to 3.5V per cell even though I have 3 different BMSes in my setup. The reported soc can spread 7-10%

 

[Alkaline]

SOC is a BMS calculated value..
So unless all cells are in balance, and all batteries are in balance, SOC isn't a good value to go on.

Off-grid garage will give you good explaintion on how this BMS works ( jakiper also uses the PACEbms)

what the heck I thought he said he liked the pace bms?

 

[Quattrohead]

Come on man get real you know he likes whatever needs to be sold this month ??

 

[houseofancients]

Come on man get real you know he likes whatever needs to be sold this month ??

Yeah, then again, he does do a good job in explaining BMS settings and general menu structure, which is helpfull for a lot of folks..

Also " the grass is always greener at the neighbors" sometimes come to mind, so I absorb what I think is usefull , and ignore what I think is a sales pitch

 

[Ben@Fogstar]

Hi Mike,

I charged all mine to 100% seperatley before connecting them together, via the inverter. I think the SOC differences are superficial and probably due to current calibration between different BMS. Also, each pack will be a slightly different capacity. Mine do sometimes differ by a couple of percent, but then sort themselves out.

 

[Oldman2]

I have just 2 batteries connected today, this one has been at 99% and 1000mAH short of full for 30mins or more, its now balancing, I would like to know why it cant make the 100% capacity? Full charge volts are set at 56v and 2amps pack full charge current. Balance threshold is 3.45v and Vcell is 20mV.

 

[Oldman2]

After about 1hr the same battery still with BL on 11 of the 16 cells suddenly is 100% and the remain capacity jumped the 1000mAH it was short.
I now have cell 10 OV alarm and it seems to me that The inverter isn't supplying charge any more under 2amps but the other battery is? when one battery is discharging the other is charging. Both now have alarms for OV one being 3690mV and OVProtect has kicked in.

 

[Quattrohead]

It is still balancing, when done with that it should be 100%, if not at that point you can reset the SOC to 100% if you have that option.

 

[Quattrohead]

Both now have alarms for OV one being 3690mV and OVProtect has kicked in.

This is not ideal, weakest cell in the pack. Try knocking down your charge voltage a bit, maybe 1v.

 

[DIYrich]

Pic of your parameters tab.
Your BMS settings are too close to the inverter charge settings. My vcell is 5mv.

 

[houseofancients]

Pic of your parameters tab.
Your BMS settings are too close to the inverter charge settings.

When running communication, BMS setting trump inverter settings.
It is still not clear to me if OP now has set his inverter to AGM, using. Voltage settings earlier provided, and disconnected the comm cable

 

[Oldman2]

@Quattrohead I have adjusted the full charge volts to 55.20v which I believe is full charge for the Fogstar pack.
Here is the current parameter page @DIYrich.

 

[Oldman2]

When running communication, BMS setting trump inverter settings.
It is still not clear to me if OP now has set his inverter to AGM, using. Voltage settings earlier provided, and disconnected the comm cable

I really dont know how to do what you ask. When I first got the Fogstar batteries I tried using user defined battery settings and it was a bit of a disaster with lots of alarms.

Below is the default list of settings.
Battery capacity 100A
Discharge depth 80%
Overcharge SOC 95%
Overdischarge SOC 20%
I max charge 60A
I max discharge 60A
Charge OVV-pro 56.4v
Discharge UNV-pro 46v
Battery OVV-pro 59.5v
Battery UNV-pro 46v
Floating volts 55v
Floating current 3A
Floating time 30mins
Equalising volts 55v
Equalising time 000day

 

[SeaGal]

Few thoughts... it seems @Ben@Fogstar posting is saying same as I did in post #5 - that the difference in SOC is probably just down to the differences in the BMS measuring the state of each battery. As they packs are all connected in parallel and all using grade A cells, hopefully there is not too much real-life difference in the SOC of each pack.

With regard to BMS settings and balancing, if it were me, I'd make some changes...

First, OVP for cell of 3.7V is too high. It should be 3.65V max.
It would be OK to set OVP for cell to release sooner than 3.38 though.. maybe 3.45V?

Secondly, I'd set the balancing to start at 3.4V, not 3.45V and at 15mV difference.

Lastly, is there a way you can limit charge current when above say 95% SOC. The screen is showing a charge current of 20A at 99% which is quite high. That means the cells will peak voltage very quickly - much more quickly than a passive balancer can do its job to balance. If you can slow the charge current down, then the balancer will have more time to do its job.

Finally (if you can have a finally after a lastly!!), with Pack FullCharge Voltage set to 55.2, I don't see why the pack is not reporting 100% SOC when you have a pack voltage of 55.8V. Or even why it is still charging at 55.8V when full charge voltage has been reached - but maybe you changed settings between those two screenshots?

 

[Oldman2]

Thank you @SeaGal for the pointers, I have made the changes you suggested OVP 3.65V OVP release 3.45V
Balancing at 3.40V but the lowest Vcell I can set is 20mV

I'm not aware of anything I can change to limit the charge current at 95% SOC
I will monitor to see what happens at 55.2V and above as I don't remember if the setting was changed after the screenshot or not.
Today with healthy sun to charge with I watched PbmsTools with all 3 batteries getting to 99% then with reduced current all 3 hung there for 30mins or more with no sight of alarms, they all changed to 100% and have stayed that way for 4hrs. Pack volts are 53.44 to 53.48V Cells Max are 3338 to 3342mV with differences of 1 to 4mV across 3 batteries. I have seen no attempt at balancing taking place at all.

 

[SeaGal]

I have made the changes you suggested OVP 2.65V OVP release 3.45V
Balancing at 3.40V but the lowest Vcell I can set is 20mV

3.65, not 2.65 I hope!

 

[Oldman2]

3.65, not 2.65 I hope!

LOL yes 3.65 time to do a quick edit

 

[Oldman2]

My 3 batteries were full charged by 2pm today.
Bat1 was 6.81A 55.795V pack volts 100% and balancing,
Bat2 was 6.40A 54.529V pack volts 100% no balancing
Bat3 was 8.29A 54.762V pack volts 100% no balancing.
No alarms and Amps dropped to zero on all after a few mins.
Looks like another sunny day tomorrow so I will see how close together they are then