EXT IO for diversion load control? Sbms40

[Levi Clark]

Am I mistaken in thinking that I can use the EXTIO3 pins to turn a SPDT relay and divert the solar load into like a hot water element?

Would the EXT IO 3 or 4 have enough amperage to work a 24v relay coil? 

I have a 24v system for a freezer bank and when the freezers' batteries are full (typically all summer) I would like to divert that load into something else with the use of a big ol' relay..

I could also use a smaller relay from the EXTIOx pin to then power the 24v coil if needed, would that be okay?

I understand that the newer SBMS0 has the SSRs that basically do this exact thing but I still.have a SBMS40 that works very well.

Thanks a million for the awesome product and service you provide everyone!

Levi

[Dacian Todea (electrodacus)]

Levi,

The EXT IO3 or 4 can not directly control a relay coil and also you will need to invert the logic anyway.  So you can use some SSR that can handle a relay coil or you can use something like Victron BP65 (not that much more expensive than a good relay).

You can also build something with a power transistor that both inverts the signal and controls the relay.  You will want something like EXT IO4 set as type 1 that way it will be open circuit when charging is not needed thus EXT IO4 can short the base or gate of a trasitor/mosfet keeping the transistor OFF until charging is no longer needed then it becomes open circuit allowing the transistor to pull the relay coil to GND energizing the relay (a diode will also likely be needed to handle the coil stored energy).