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QUCC 500A BMS connection to inverter

theologu

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Oct 5, 2021
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Hello guys!

I am the happy owner of a QUCC BMS 500A, 4 contactors, 2 pre/dis/charge resistors and hall sensor - the full package from QUCC :) . This BMS has distinct charge and discharge contactors, and on each of them it can do pre-charge or pre-discharge with additional contactors and an resistor (50R, 100w). It looked simple when I ordered, but now I am trying to figure out how to connect it in an efficient way to the hybrid inverter, that does charge/discharge on the same port.

So, for short, my battery bank will be a 16S2P setup with 32x 302A CATL LiFePo, resulting (hopefully) a 48V ~600A bank. My inverter is an DEYE SUN-12K-SG04LP3, 12KW 3P; I plan to not discharge more than 200A, and charge with less, let's say 100A, but this is not extremely important now.

On their Aliexpress product page, they show multiple connection methods: https://www.aliexpress.com/item/1005002859512726.html?spm=a2g0s.12269583.0.0.721673bdhS9yIN

What should be the best connection method and schematic btw the BMS/contactors/inverter ?

qucc_full_pack.JPG
ch_dsch.JPG

discharge_preamp.JPG

They also list some MD* diodes or diode modules (MDC, MDK), 50-350A/1600V ; my fear is that such diodes will have a significand voltage drop and impact the performance of the system.
Any advice is welcomed....

Thanks,
 
I have the same system I struggled with this a bit myself. I wont get into my use case as it is very specific to a marine installation.
In the end I realized it is of little concern, here is why:
The BMS is not a charge and discharge controller, it is for battery PROTECTION this is an important distinction.
The BMS should NOT disconnect your batteries from load under normal circumstances those Low Volt settings should be in the Inverter.
The BMS should not be the charge cutoff mechanism under normal circumstances, those settings should be in the High Volt settings in the MPPT.
The BMS only gets involved if the cells are out of balance
and ONE cell starts hit HV before the pack as a whole (when the pack reaches full SOC the MPPT should stop charging.)
or if ONE cell hits LV before the pack as a whole (when the pack reaches Low SOC the Invertor should drop the load)

Now the diagram you choose is a single charge discharge system (hybrid inverter/charger with internal MPPT All-in-one, which is my case)
If you are not using a hybrid, then you would not need the diodes, the charge relay would go to an independent MPPT unit and the dischrage relay would go to the inverter only.

Given the above the diode/rectifiers come into play very infrequently with an All-in-one, only during a "miss-managed" or fault state.

Starting with all relays open, there is no flow thru the diodes, Assuming the battery is healthy at this point not HV nor LV.
When the BMS Discharge is turned "ON", first the Pre-charge closes for a moment, then Discharge closes, and current will flow thru the diode to the Inverter. Then the BMS Charge is turned "ON" Now the diodes are completely bypassed and have no afffect

1643561907281.png1643562167584.png


Normal operation, no diode current flow.
1643562519695.png

Now the "fault modes" will cause flow thru the diodes with losses, but only until the pack returns to a normal state.
But these are only to protect the cells it should not be used as an on/off for the inverter or on/off charging.
Low Volt cutoff the discharge relay would open, IF the inverter can still supply enough charge current from the Solar or charger then the charge relay would still be closed and current will flow thru one diode.
1643563178796.png
Similar for HV cutoff of charging, Inverter can still draw power, which should eliminate the HV and return to normal at some point.
But both of these situations should rarely occur if the Inverter/Charger/MPPT settings configured to kick in slightly before "BMS Protection"

1643563279611.png
 

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Thank you @hughespat57 for taking the time to describe the flows and for the drawings. You are totally right, meantime I had some discussions with Qucc support - while there's a language barrier and they are not focused on solar, they are very supportive and tried to answer all my questions. I will make this setup and hopefully return here with positive feedback. It will take me some time to build the whole thing and i have some delays, but nonetheless, it will happen :)
Regarding Qucc BMS communication with Deye/Sunsynk/SolArk inverters, based on my research it will not happen out of the box. Deye is not willing to work and integrate integrate with Qucc. There is hope anyway, I've seen people doing it by reading on RS485 modbus registers from BMC and publish the data on CAN, using Pylonthech registers, that most of the inverters recognize. This can be done with an arduino or a raspberry pi, I am posting here few links, maybe it will save somebody's time:

 
While it certainly would be nice if all the devices played well together, it never seems to be the case.
I use the battery app to monitor over all health and cell balance other than that I do everything from the Inverter.

I set the BMS to 10% SOC low disconnect or if any one cell hits 5% (3.00 volt). 90% SOC charge disconnect or any cell hits 95% (3.50 volt)
Inverter is set to 20% SOC load disconnect, 80% SOC charging stop.
So BMS limits should only kick in if I have an inverter fault of some kind.
 
Hi & help,
What can anyone tell me about the 4S version? They show one but I can't get to buy one yet! Also is there any user manual available?
Marine system with a 3000watt inverter so it will pass some hi currents & I am not interested in mosfets. Cells have come down since the last boat I had but now the cost of the BMS has made things & the many to choose from, is not making it an easy job!
Regards Bill
 
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