Renogy DC-DC schematic review

[Mike N]

I wanted to run this Renogy DC-DC schematic by the group and make sure I have this correct. I striped out most of the rest of my system to simplify the view. I've been using Gemini for help and I wanted to double check that EXTIO5 doesn't need a resistor as the SSR limits its current from 5 mA to 20 mA. I was planning on using a SSR with these specs:

Model SSR-25DD
Control method DC to DC
Control (Input) Voltage 3-32VDC
Load (Output) Voltage 5-220VDC
Min Control Current 5MA
Max Control Current 20MA
Current & Frequency 25A

Insulation Resistance 500M Ohm/500VDC
Off Leakage Current ≤5mA
On Voltage ≤1.6V
On-off-Time ≤10ms

Thanks, Mike

[Dacian Todea (electrodacus)]

Mike,

Unfortunately looking at the Renogy manual this model has the IGN signal as optional. That means SBMS can not turn OFF the charging using that signal.

While IGN is 0V disconnected the Renogy can consider that you are not using the IGN and run in Automatic mode ignoring the IGN.

If you already purchased this model the only safe way to use it to charge a Lithium type battery is to have a way for SBMS to disconnect the positive input from starter battery.

[Mike N]

Thanks Dacian , I fundamentally misunderstood how the ignition wire worked, it's more of a mode changer than a switch. lesson learned, don't buy something on "Prime Days" before you need it and then wait a month to implement it. 

I'll switch at the positive per your suggestion or pay up for the Victro unit. It's really just a backup until I get solar going and maybe for winter.

When I use a the SSR to switch the positive is it correct to say the EXTIO5 doesn't need a resistor as the SSR limits its current from 5 mA to 20 mA?

Thanks again the great product support, Mike

[Dacian Todea (electrodacus)]

While the SSR limits the current you will still need a resistor in order to protect the EXT IO5 in case of accidental short to GND of the wire. So if you connect EXT IO5+ to +12V battery and then EXT IO5- connects to GND (Battery negative) by accident it will damage the EXT IO5 but if you have a 270Ohm or so resistor to Batt+ before getting to EXT IO5+ then both the wires and the EXT IO5 are protected as the resistor limits the current.

The Victron BP65 can be directly controlled by EXT IO5 and is decently low cost (at least it was last time I checked).