SBMS0 Resistors and Flyback Diodes

[Andre Samson]

Hi, hoping someone can explain when and where (and what values) to use resistors and flyback diodes in an Electrodacus SBMS0 setup? I can't seem to find a clear explanation.

I'm using this in a campervan with 3 panels, and will have BlueSeas 500a disconnects for load and charge. They will have optocouplers between them and the SMBS0 to bridge the switching load. Also have a Midnite Solar MPPT panel controller that's already installed in the van, so I will keep using that to run the panels. The SMBS0 will only see a charging source from them.

I believe the flyback diode has to go on any relays/optocouplers that aren't DSSR20s or 50s. Not sure where the resistors go. No idea on type or values.

[Andre Samson]

Also, what is recommended for an SSR or other relay to control the BlueSea relays?

[Dacian Todea (electrodacus)]

What is the exact model of that BlueSeas relay ?

The SBMS0 EXT IOx outputs are all optoisolated and they will be either Open circuit (for OFF) or Close circuit (for ON) and max current allowed when close circuit is 50mA.

The SBMS0 requires that charge sources are controlled ON/OFF separately from loads and SBMS0 needs to be able to control ON/OFF all Loads and separately all charge sources else it can not protect the battery.

I do not know what model of Midnite MPPT you have but some have a AUX port that can be configured to be able to be controlled by an external BMS.  The SBMS0 needs to control ON/OFF your MPPT as the MPPT has no idea when to stop charging as it can not see the individual cell voltages.

[sailingharry]

If you are talking about the Blue Seas RBS (Remote Battery Switch), I'm about 95% (or more!) sure that the control wires (which you connect the SBMS0 to) are truly control wires -- their current is measured in mA or even microamps.  They don't actually operate the switch, they activate internal circuitry and the power for the operation comes from the connected battery.