Classic 200 SCC & LFP BMS shut off

[dRdoS7]

Hi,

I had a quick search through a few pages of posts, back to 2018, and didn't find anything.

I have a Classic 200, ATM connected to a NiFe 48V battery bank, and am replacing those with an LFP 48V bank & BMS.

There's 7Kw of panels connected to the Classic.

My question is: would it possibly damage the Classic if/when the BMS shuts off the battery?

There is also an inverter, which will be connected to the same point on the BMS, so that will also be shut off, though not from the Classic.

The inverter can run batteryless, so it would keep running, off it's own 3kW solar.

I have tested by shutting the inverter DC battery switch, but that was early morning, and not much sun.

Thanks,

dRdoS7

[mahendra]

Does this BMS cuts power to the Inverter and charge controller by use of a solid state relay?
If so in my opinion it not the wisest scenario to use.
I use midnite wbjr to tell my batteries when to float and the classic to tell the inverter whe. To shut off when it goes beyond my soc set point.
I had an after marken BMS but that posed a series of Complications so I just removed it and use the wbjr.
I had mention the only draw back of the wbjr is that it does not monitor individual cells. But some persons on this forum has install separately individual cell monitors to their pack. From my experiences it is not required but can definitely be a good addition.
Just ensure they are balanced properly.

[dRdoS7]

Hi,

Does this BMS cuts power to the Inverter and charge controller by use of a solid state relay?
If so in my opinion it not the wisest scenario to use.
I use midnite wbjr to tell my batteries when to float and the classic to tell the inverter whe. To shut off when it goes beyond my soc set point.
I had an after marken BMS but that posed a series of Complications so I just removed it and use the wbjr.
I had mention the only draw back of the wbjr is that it does not monitor individual cells. But some persons on this forum has install separately individual cell monitors to their pack. From my experiences it is not required but can definitely be a good addition.
Just ensure they are balanced properly.

I'm not planning on running my LFP bank without a BMS.

Could you explain why this is not wise? What were the complications?

The Classic & Inverter will both keep the bank within voltage specs, but neither can tell if a cell goes out of spec. Hopefully the BMS will do it's balancing correctly, and there will be no need to shut off the battery. I want to know if this happens, could it damage the Classic?

Thanks,

dRdoS7

[mike90045]

I don't think it's good to have solar panels producing 140V with the classic battery terminals disconnected.   That places the system into Voc and eventually the battery side of the classic may see the PV voltage
I know for sure battery voltage, at night, bleeds thru to the PV side and lights up the SPD on the array pole

[dRdoS7]

Hi,

Hi,

Does this BMS cuts power to the Inverter and charge controller by use of a solid state relay?
If so in my opinion it not the wisest scenario to use.
I use midnite wbjr to tell my batteries when to float and the classic to tell the inverter whe. To shut off when it goes beyond my soc set point.
I had an after marken BMS but that posed a series of Complications so I just removed it and use the wbjr.
I had mention the only draw back of the wbjr is that it does not monitor individual cells. But some persons on this forum has install separately individual cell monitors to their pack. From my experiences it is not required but can definitely be a good addition.
Just ensure they are balanced properly.

I'm not planning on running my LFP bank without a BMS.

Could you explain why this is not wise? What were the complications?

The Classic & Inverter will both keep the bank within voltage specs, but neither can tell if a cell goes out of spec. Hopefully the BMS will do it's balancing correctly, and there will be no need to shut off the battery. I want to know if this happens, could it damage the Classic?

Thanks,

dRdoS7

I was reading other posts, and saw one you had started on Lithium. I noticed that your BMS was at fault.

I would be interested in hearing why it's not wise to use a BMS.

I don't think it's good to have solar panels producing 140V with the classic battery terminals disconnected.   That places the system into Voc and eventually the battery side of the classic may see the PV voltage
I know for sure battery voltage, at night, bleeds thru to the PV side and lights up the SPD on the array pole

So, you had a night light! 

In all seriousness, do you think the battery side of the Classic will get PV voltage?

Maybe I should put a solenoid/SSR in the PV & Classic outputs, so the BMS shutdown can turn them off (via a voltage controller).

Thanks,

dRdoS7

[boB]

I don't think it's good to have solar panels producing 140V with the classic battery terminals disconnected.   That places the system into Voc and eventually the battery side of the classic may see the PV voltage
I know for sure battery voltage, at night, bleeds thru to the PV side and lights up the SPD on the array pole

The diode FETs are what allows the small amount of current to pass from battery to PV input with 10K of resistance.  Current should not pass the other way.

[dRdoS7]

Hi,

I don't think it's good to have solar panels producing 140V with the classic battery terminals disconnected.   That places the system into Voc and eventually the battery side of the classic may see the PV voltage
I know for sure battery voltage, at night, bleeds thru to the PV side and lights up the SPD on the array pole

The diode FETs are what allows the small amount of current to pass from battery to PV input with 10K of resistance.  Current should not pass the other way.

Any thought on what will happen if the battery is suddenly disconnected? Bad thing to do to the Classic? Imagine it happened in full sunshine in Spring, at Noon. With a depleted battery bank. Just as a cloud has passed.   OK, it wasn't full sunshine.

I am hopeful that it will not occur, but Murphy's Law suggests it is likely to.

Thanks,

dRdoS7

[mike90045]

I think it would be much better for the BMS to shutdown the Solar PV input to the charge controller, which will stop all solar charging and pose no risk to the controller.   Getting gear to interrupt the potential 150V 40A (or whatever your array is) could be tough, maybe a ganged breaker, but that would require a manual reset.   Probably a good idea anyway, if your BMS trips , you need to understand why it went off and clear the problem

[mahendra]

 I agree. This is what I was trying to point out.
The wbjr is a battery monitor but with some drawbacks as I indicated.