Shunt Resistance Value

[Dustin Dudley]

(1) I have 2 Ram Meter 500 Ampp 50 DCmV DC Current shunts on my primary system (PV & Battery). I do not know how to calculate the proper shunt resistance value. Any help? 

(2) After that, I need to verify the following as I am starting over re-programming my SBMS0 and have some things that I think are true, outlined below. If someone wants to help me verify that those assumptions are correct, that would be great also.

(3) My battery system consists of 32 280Ah Eve Lifepo4 cells in a 4p 8s configuration. I assume this means that my Battery Capacity should be set as "1120 Ah". Is this correct?

(4) I assume I should first turn off the PV breakers, generator, all 120v breakers, and the Quattro. Then program the SBMS0 with the following “Parameter Settings.”

          1: Predefined batt: 1LFP

          2: Number of cells: 8

          3: Battery Capacity: 1120Ah??

          4: Store Parameters

          5: Remove 12pin connector and reconnect for new stored parameters to be accepted

 Then I want to verify or reconfigure “Advanced Parameter Settings”

 I assume this operation also requires that all PV breakers, generator, all 120v breakers, and the Quattro need to remain turned “off.”

          1: Remove 12pin connector

          2: Verify which EXT locations are used for turning on and off my MPPT’s and my Quattro for charge & discharge

          3: Calculate shunt resistance value: (500A 50mV shunt would be ??? mOhms) Need help here....

          4: Program shunt resistance value

          5: Verify that EXT I04 is connected to my charger and that it is set to “type 1”.

          6: To test this, set EXT I04 to type “0” to see if charging stops, then back to “1” to see if charging starts back up

[Dacian Todea (electrodacus)]

(1) 50mV/500A = 0.1000mOhm

(3) Yes 1120Ah will be the rated capacity. Usable may be slightly lower but unless you want to measure the capacity for a more accurate number this is what you will write in the SBMS parameter settings.

(4)

1: Yes 1 LFP (make sure you select and push OK even if it is already type 1 LFP as when you do this all advanced parameters will be set to default in case you made changes in the past).

2: Yes 8

3: Yes 1120Ah

4: Yes push Store Parameters and wait few seconds to finis writhing

5: Yes you need to power cycle for the new parameters to take effect.

Yes you will want 0A trough the current shunts during power up but if all is connected correctly the SBMS0 will keep everything powered OFF during the power up process but some equipment like Quarto may still have some standby current while powered OFF trough the remote ON/OFF control.

The reason for all to be OFF is so that SBMS0 can calibrate the current shunt offset to zero.

One important thing is that when you set the value for current shunts and the EXT IOx you need to go to Device settings menu and push the Save device settings so that the settings you made to shunts and EXT IOx remain permanently stored even after a power cycle.

Changes to any other settings except for those done in Parameter Settings menu do not require a power cycle to take effect. So say you change the EXT IOx after you did the power cycle all you need to do is go to Device settings and push the Save device settings so that it is permanently stored in case sometime you will power cycle the SBMS but power cycle is not require other than at first installation when you set the battery type.

[Dustin Dudley]

Thank you. I performed all of those tasks. My shunt values were wrong. Disconnecting loads and charging prior to these modifications and then saving those changes followed by disconnecting the 12 pin connector for a little bit then reconnecting it resulted in the BMS saying 50% SOC for a few minutes until CFET stopped charging. At that point the SOC reported by Victron and the SOC reported by SBMS0 synched up at 100%. Now the system is cycling normally. I will make a separate post in a few minutes to dive down my next "rabbit hole" relating to this system.