Victron shunt suggestion

[STW]

Here is an idea I hope Victron will read and implement.

We need a new feature on a shunt. We need a shunt that can OUTPUT a voltage based on a state of charge.

The problem is that most auto generator start systems don’t work with Lithium batteries. It’s not that a Lithium battery can’t start the generator, it’s because the Lithium battery voltage doesn’t really change as the battery state of charge goes down. The gen start systems rely on voltage to determine when to start generator.

If we had a shunt that included a port that OUTPUT a voltage based on the SOC, we could use that to trick the auto gen start. So basically at 90% SOC the port would output a voltage of 12.5, at 50% it would output a volatage of 12.06, etc. Implementing this on a shunt would be relatively inexpensive and not require other high priced equipment (Multiplus, Cerbo, etc).

Does anyone know if this exists already? Or do you think this is a good idea (I’m sure others have thought of it as well).

 

[Crowz]

Here is an idea I hope Victron will read and implement.

We need a new feature on a shunt. We need a shunt that can OUTPUT a voltage based on a state of charge.

The problem is that most auto generator start systems don’t work with Lithium batteries. It’s not that a Lithium battery can’t start the generator, it’s because the Lithium battery voltage doesn’t really change as the battery state of charge goes down. The gen start systems rely on voltage to determine when to start generator.

If we had a shunt that included a port that OUTPUT a voltage based on the SOC, we could use that to trick the auto gen start. So basically at 90% SOC the port would output a voltage of 12.5, at 50% it would output a volatage of 12.06, etc. Implementing this on a shunt would be relatively inexpensive and not require other high priced equipment (Multiplus, Cerbo, etc).

Does anyone know if this exists already? Or do you think this is a good idea (I’m sure others have thought of it as well).

Actually you just adjust the generators start voltage to match the battery banks desired soc.

So either change the generators settings or add something to subtract voltage from the wire feeding the generators voltage check.

I know the voltages are not the same as a lead acid battery but they do change as the soc declines. Its how I have my battery chargers setup to charge my lifepo4 battery bank if it gets to low from lack of solar charging during days of bad weather.

 

[wholybee]

Here is an idea I hope Victron will read and implement.

We need a new feature on a shunt. We need a shunt that can OUTPUT a voltage based on a state of charge.

The problem is that most auto generator start systems don’t work with Lithium batteries. It’s not that a Lithium battery can’t start the generator, it’s because the Lithium battery voltage doesn’t really change as the battery state of charge goes down. The gen start systems rely on voltage to determine when to start generator.

If we had a shunt that included a port that OUTPUT a voltage based on the SOC, we could use that to trick the auto gen start. So basically at 90% SOC the port would output a voltage of 12.5, at 50% it would output a volatage of 12.06, etc. Implementing this on a shunt would be relatively inexpensive and not require other high priced equipment (Multiplus, Cerbo, etc).

Does anyone know if this exists already? Or do you think this is a good idea (I’m sure others have thought of it as well).

Yes, it exists, more or less. The Victron BMV-712 (which is similar to the smart shunt but has a display) also has a relay output which can be set to trigger on SOC. If you need a voltage, just connect the battery + to the relay common. Then connect the N/C output to the generator. When the SOC drops below the setpoint the relay will open, and the voltage drop to zero.

 

[Rocketman]

Also, you can connect a Cerbo, and the Cerbo also has a Generator start/stop functions with several different options.

The Victron is just a 2wire on/off. If you need additional starting electronics (for example a Onan 3-wire system) Atkinson electronics makes a generator electronics module that allows almost any inverter to start almost any generator.

 

[STW]

Most gen starts say they don’t support lithium. Probably because they don’t recognize the higher voltage (13+).

I am not sure if the gen start sees NO voltage if it will try to start. Onan manual says it won’t start under 9 volts.

I just bought an Onan ECS-AGS+ and it states it will not work with lithium.

https://cssna-ec.cummins.com/pub/AGSCompatiblityChart.pdf

 

[marionw]

Victron shunt VE.Direct connection is really an RS232-TTL port. Use an Arduino and you can react to voltage and/or SOC

 

[STW]

Victron shunt VE.Direct connection is really an RS232-TTL port. Use an Arduino and you can react to voltage and/or SOC

That solution will be beyond 99% of the users.

Thats why I was suggesting Victron build it in as a feature of their shunt. It takes out the voltage difference problems between lead acid and lithium. It could be programmable via their app for voltage curve. It would be simple for any user to implement.

 

[STW]

Also, you can connect a Cerbo, and the Cerbo also has a Generator start/stop functions with several different options.

The Victron is just a 2wire on/off. If you need additional starting electronics (for example a Onan 3-wire system) Atkinson electronics makes a generator electronics module that allows almost any inverter to start almost any generator.

Was looking for a lower cost solution that doesn’t require a user to implement an entire eco system. A shunt is simple to add to a system… it just needs this added feature to be very valuable to a ton of users.

 

[STW]

Yes, it exists, more or less. The Victron BMV-712 (which is similar to the smart shunt but has a display) also has a relay output which can be set to trigger on SOC. If you need a voltage, just connect the battery + to the relay common. Then connect the N/C output to the generator. When the SOC drops below the setpoint the relay will open, and the voltage drop to zero.

Won’t work as the gen start won’t try to start if <9v is seen.

 

[wholybee]

Won’t work as the gen start won’t try to start if <9v is seen.

Then use 2 resistors to make a voltage divider. I'm not that familiar with many generators, but don't most have a remote start connection that will start the generator on a contact closure?

I think you are over estimating the difficulty in adding the feature to the smart shunt. It is obviously possible, but it is a niche feature that few people would use, and would add significantly to the complexity and cost.

 

[timselectric]

Most generators have a two wire remote start option.
I have never seen one that watches battery voltage. (Other than the on board battery)

 

[STW]

Most generators have a two wire remote start option.
I have never seen one that watches battery voltage. (Other than the on board battery)

All of Onan and Magnum gen start modules use battery voltage to determine when to start generator. Look up the Onan EC-AGS+.

 

[STW]

Then use 2 resistors to make a voltage divider. I'm not that familiar with many generators, but don't most have a remote start connection that will start the generator on a contact closure?

I think you are over estimating the difficulty in adding the feature to the smart shunt. It is obviously possible, but it is a niche feature that few people would use, and would add significantly to the complexity and cost.

Everybody with an RV that wasn’t designed for lithium… so 99% of them could use this feature.

 

[STW]

This feature could also be used to FIX the built in battery monitors in RVs. These simple 5 light indicators rely on voltage values to indicate SOC. They could be wired to the shunt port feature mentioned so they could continue to operate correctly.

 

[timselectric]

All of Onan and Magnum gen start modules use battery voltage to determine when to start generator. Look up the Onan EC-AGS+.

This makes zero sense. Generators are mostly used as a backup power source.
Are you referring to dedicated battery charging Generators?

 

[wholybee]

Everybody with an RV that wasn’t designed for lithium… so 99% of them could use this feature.

So there is no way to manually start the generator except by opening the panel on the side of the RV? There is no control panel inside with a remote start button? Similarly no way to disable the generator so it won't start if you don't want it to? That doesn't make any sense. As I said, the BMV-712 would give a real SOC indication (since you mentioned the 5 light indicator) and connect the relay to the remote start switch. If you don't have a remote start, figure that out. There *is* a way.

You CAN NOT determine the state of charge of a Lithium battery by voltage. You might rig something so the generator will start somewhere between 10% and 40% but you would never exactly know where in that range. And the 5 light meter based on voltage simply won't ever work. Replace the 5 light meter with a BMV-712.

 

[wholybee]

All of Onan and Magnum gen start modules use battery voltage to determine when to start generator. Look up the Onan EC-AGS+.

But they must also have other controls, a remote start, a generator disable, etc. For sure, the Onan generators I have seen absolutely did have those features. Start digging into the manual.

 

[OzSolar]

All of Onan and Magnum gen start modules use battery voltage to determine when to start generator. Look up the Onan EC-AGS+.

Sounds like you just need to get one of them then.

In the bad old days of lead acid it was the only option and it was terribly unreliable.

IMHO, there is zero chance that any manufacturer today would be naive enough to solely use battery voltage as a state of charge indicator for controlling the generator to charge LFP batteries.

 

[wholybee]

All of Onan and Magnum gen start modules use battery voltage to determine when to start generator. Look up the Onan EC-AGS+.

Just looked up the EC-AGS+. See page 13 of the manual, it supports a remote start/stop switch. Connect that to the relay on the BMV-712.

https://www.cummins.com/sites/default/files/2021-05/A065F574_I2_202106.pdf

 

[STW]

Just looked up the EC-AGS+. See page 13 of the manual, it supports a remote start/stop switch. Connect that to the relay on the BMV-712.

https://www.cummins.com/sites/default/files/2021-05/A065F574_I2_202106.pdf

The EC-AGS+ is using the remote switch connection to start the generator….. but 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. This could be wired to a shunt that output a voltage showing SOC that mimics a lead acid battery.

I also research Victron solution, but it seems it doesn’t work as simple as it sounds with an Onan generator.

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Again,most are not looking for a gen start replacement. They want to use what they already got, but somehow make it work with lithium. Easiest way I could think of was if the shunt sent a voltage that mimicked lead acid SOC.

Also most gen starts in RV provide more features than simply starting on voltage. They also start on temperature. To me this is most critical because if pets are in RV you want the gen to start so AC can run.