QQ (quick question)
How many shunts do I use for a 2 batt system using (1) REC 9M master and (2) REC Slave units?
From this diagram, each battery has it's own shunt. This makes sense. Do I also use another Shunt to show total in/out current to rest of the system which will include a WS500, MPPT solar, and the 3x MultiPlus II inverters?
Good question,
In this configuration you will only need 2 shunts. You set the shunt coefficient in the Master and it will broadcast it to both of the slaves. The Master will take the sum of all connected slaves and use that value. Highest and lowest cells are also monitored by the Master and dsplayed. Here is what they look like on the Victron
Cerbo. And here is a link to an updated diagram: https://rec-bms-na.com/download/39/rec-master-slave-bms-sketches/1337/rec-2q-master-slave-parallel-victron-ws500-example-2.pdf
hmm...
Does matter that I am using the 1Q units as slaves and NOT the 2Q's?
If I understand correctly, I only need a shunt for each battery. In my case I need two 1,000A shunts as each battery consists of 32 CALB 230 cells arranged as a 4P8S battery. I will be able to see current flow from each battery and the 9M Master BMS manages communications to the outside world?
no, the 1Q's are fine too. You will be able to see the total current flow from the the Master. To check that each shunt is working, jut power off one pack to verify each bank is working correctly.
If you have older firmware you will need to set the coefficient for each slave through the Master in the Manual commands section. Just select your slave address when issuing the command
The shunt only gets installed at the Master when you have a high voltage series connected system.
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