Trying to integrate two SSR's and a VEDirect cable in one EXTIO circuit

[Egbert Jager]

Good morning from Malaysia,

Before I start on my question I want to thank Dave and Chris for their help. The BlueSea 7713 switches are controlled, simply, by the SBMS0 on EXTIO3 and EXTIO4 with the (included) remote switches wired in series. I haven't added the switch LED lighting wire yet, but that's a later project.

My present project is the wiring of the control circuit for the charging sources, preferably all on one EXTIO.

They are: 

Victron Smart Solar 30/100 MPPT through the VE-Direct Cable (only one now but looking to add to more panels on a second identical controller.)

Meanwell NPB 750-12 Battery charger. This can be remote-controlled by shorting pin 8 (12V+) with pin 7 (ground). I anticipated using a Fotek DDSSR

Alternator via external regulator MC-614. I anticipated using a Fotek DDSSR to open and close the ignition wire circuit.

I will try to include a (very) rough sketch without the second MPPT, in a response as my laptop is failing me right now...., . My electronics ability hasn't reached a point where I can confidently say what resistors I need to make this happen safely.

Any help would be greatly appreciated.

[Egbert Jager]

[Dacian Todea (electrodacus)]

In order to protect EXT IO5 assuming about 14V max battery voltage and around 50mA max current allowed trough EXT IO5 the resistor on EXT IO5+ can be as low as 270Ohm in case EXT IO5- is shorted to GND 14V / 270Ohm = 52mA

The VE direct I think only requires about 1mA so voltage drop on the 270Ohm resistor will be 0.001A * 270Ohm = 0.27V

It is hard to say what current the DSSR's requires as those Fotek are build in different factories with very different components and design.

But say they require 3mA each to work properly so 6mA in total

Then total voltage drop on the 270 Ohm resistor will be 7mA * 270 Ohm = 1.89V

Say 12V battery - 1.89V = 10.11V so sufficient for the VE.direct that require a minimum of 6V to work.

With about 10V at that point and assuming about 5V on the DSSR when 3mA are pushed trough you have the 10V - 5V = 5V delta dropping on the resistors  and so with 3mA trough resistor and 5V drop on it you need around 1.666Kohm so 1.5 or 1.6kOhm should work fine but you need to test as those DSSR's do not have a proper spec as they are not all build the same.