Victron shunt suggestion

[wholybee]

Not sure it works that way. Your earlier post said when the relay opens the voltage drops to zero… so what starts the generator?

The remote switch they are talking about is the manual switch on the dashboard of the RV. The EC-AGS+ is using that connection to start the generator….. but it needs to determine when voltage is low. It then cranks for a predetermined amount of time and verifies the gen set starts. If not it tries again a couple times. It only has a profile for lead acid, so lithium does not work. On same page in manual it shows the hard wired connection that is uses to do the voltage detection.

It's a relay. With both N/O and N/C connections. In my other post, I said that you can connect the battery to the common terminal, and it will provide a voltage.

But it is just a relay. You can connect it to the Y cable (you will need the pinouts and signal descriptions of the wires) and it will start the generator just like the controller does. It won't have the smarts to check that it starts and try again, that would be some additional logic you would need to add if you want it. Or, just connect the relay to the switch on the dashboard of the RV. That was one of my earlier suggestions, just connect the relay to the remote start. Simple as can be.

As I said, the voltage detection part will not work with LFP, because the LFP voltage curve is very flat, but voltage will still go up/down based on load or charging. It just doesn't work.

 

[STW]

I appreciate the comments, but I feel like we are not on the same page. Let me try to explain.

This is for an RV gen start solution. I know there are MANY solutions possible, but the goal is to not replace working equipment. Many RVs already have a gen start built into them. The problem is they only have lead acid profiles to determine battery SOC. So when moving to lithium’s their solution fails to work as battery voltage is not reliable indicator of lithium SOC. Also these gen starts have another VERY important feature of starting based on temperature… this feature we do not want to lose. Adding this feature would require a lot more Victron equipment.

The battery monitors built into many RVs are a simple 5 light solution. I agree that is not great, but it is something. If Victron headless shunt had a voltage output it could solve the problem of letting existing equipment work as designed for a low cost. Also many may not want to install the Victron display, as it would not be needed if their 5 light monitor worked… less cutting, drilling, and routing wires to install a display they don’t need.

 

[wholybee]

I appreciate the comments, but I feel like we are not on the same page. Let me try to explain.

This is for an RV gen start solution. I know there are MANY solutions possible, but the goal is to not replace working equipment. Many RVs already have a gen start built into them. The problem is they only have lead acid profiles to determine battery SOC. So when moving to lithium’s their solution fails to work as battery voltage is not reliable indicator of lithium SOC. Also these gen starts have another VERY important feature of starting based on temperature… this feature we do not want to lose. Adding this feature would require a lot more Victron equipment.

The battery monitors built into many RVs are a simple 5 light solution. I agree that is not great, but it is something. If Victron headless shunt had a voltage output it could solve the problem of letting existing equipment work as designed for a low cost. Also many may not want to install the Victron display, as it would not be needed if their 5 light monitor worked… less cutting, drilling, and routing wires to install a display they don’t need.

I think you are wrong in assuming it will be low cost. That is the main thing. The smart shunt is a very limited device. It doesn't even have the relay the more expensive display has. You are talking about a hardware change that probably involves a more powerful microprocessor, a larger footprint, new firmware to be written, etc. And I very honestly don't think very many people would be interested at all. It is a very limited application, for which there is already a solution.

Certainly, no one from Victron is going to read this and add that feature any time soon. So, we are offering you how to do what you want, with products that actually exist. If you are looking for a solution for future RV buyers, the best solution is that the start module should had a canbus interface.

All that said, you could _probably_ get an almost working solution with 2 resistors to make a voltage divider to reduce the LFP full charge voltage from 14.2 to 12.8. The 5 light meter wouldn't work very well, but it would work a little bit. And the generator would start.
Instead of 2 resistors, you could use a potentiometer so the output level is adjustable. Something like a 5k/1W pot. Pins 1 and 3 go to the battery +/- and pin 2 is your adjustable voltage output.