Victron SmartShunt Charged Voltage Setting Question

[YurtSolar]

Tldr: Should I set my Victron Smartshunt charge voltage to just below my battery absorption voltage of 28.1v, or just below my battery float voltage of 27.0v?

I set up my Victron Smartshunt with setting values based on my Off Grid Power Solutions' excellent video. In the video (around 6:30) he recommends setting the charge voltage slightly below the bulk voltage. He says that the settings in the BMS and charger should be the same, and has his charge voltage set to 14.0 for his 12 volt system. I have seen the same recommendation in other threads like this one, that the charge voltage be set just below the absorbtion voltage.

My system is 24 volt, so I assume the equivalent would be a charge setting of 28.0. This is indeed 0.1v below the EG4 recommended bulk setting of 28.1, which is what I set as my absorption voltage on my Victron mppts. However the Victron Smartshunt manual says to set the charge voltage 0.2-0.3v below the float voltage of 27.0. Do you recommend that I set the Smartshunt charge voltage just below the absorbtion voltage like I see recommended in tutorials online, or just below the float voltage like Victron suggests? Thank you!

Running 2 parallel EG4 24v lithium batteries with recommended absorbtion of 28.1v and float of 27v.

 

[sunshine_eggo]

If charging with solar, you use 0.2V below absorption. If charging with AC powered chargers that always deliver dependable current, 0.2V below float.

Solar charging with charged voltage set based on float runs a significant risk of a false sync indicating 100% earlier than it should.

Victron Troubleshooting includes setting charged voltage based on absorption:

Section 10.3.11:

10. Troubleshooting

www.victronenergy.com

 

[YurtSolar]

If charging with solar, you use 0.2V below absorption. If charging with AC powered chargers that always deliver dependable current, 0.2V below float.

Solar charging with charged voltage set based on float runs a significant risk of a false sync indicating 100% earlier than it should.

Victron Troubleshooting includes setting charged voltage based on absorption:

Section 10.3.11:

10. Troubleshooting

www.victronenergy.com

Very helpful, thank you so much @sunshine_eggo ! I don't anticipate using my AC battery charger, but if I do use it sometime should I just change that one setting in the app while I'm using the AC charger and then change it back when I'm back to solar?

 

[740GLE]

Also make sure you set up a VEsmart network, have that shunt tell your victron SCC what the actual battery voltage is. This will avoid and losses or voltage drop on the leads for the SCC.

 

[YurtSolar]

Also make sure you set up a VEsmart network, have that shunt tell your victron SCC what the actual battery voltage is. This will avoid and losses or voltage drop on the leads for the SCC.

Update: done! I just watched one short video about the VEsmart network and connected my Smartshunt to all 3 of my SCC's in less than 5 minutes. Thank you so much @740GLE for telling me about that. What else do I not even know about that could be helpful?

Ooh! I've never heard about that, I'll have to look into it. I have 1 smart shunt and 3 75/15 SCC's. Can the shunt tell all 3 the actual battery voltage? Currently there is a good gap between the SCC stated battery voltage and the shunt stated battery voltage (see screenshot). Shunt shows way lower than the scc's..

 

[outboard1196]

Ooh! I've never heard about that, I'll have to look into it. I have 1 smart shunt and 3 75/15 SCC's. Can the shunt tell all 3 the actual battery voltage? Currently there is a good gap between the SCC stated battery voltage and the shunt stated battery voltage (see screenshot). Shunt shows way lower than the scc's..View attachment 225839

Are all the charge controllers charging the same battery bank ?
If so they should all be using ve smart network with the shunt . if you open any device in the app below history you should see the network icon . set it up ( its all Bluetooth) it improved my set up a lot when I set it up . just be aware the led indicator in the charger will flash every second . this just says in receiving data via network, I though it was an error at first .

 

[740GLE]

Yup one shunt to rule them all! Just as long as they are close enough for the BT to talk to one another.

For the cheaper smart shunt that’s something like 5-8ft.

It also hits home to have that smart shunt sensing lead as close to the true battery terminals as possible.

 

[YurtSolar]

This is amazing @740GLE and @outboard1196 I've got them all set up in network now. That was the easiest improvement of this whole system!

 

[740GLE]

So when are you getting a multiplus? Cerbo? Lynx? lol

I started with just a 100/15 and it worked okay but I knew I had losses between battery and SCC, but adding my shunt really was able to get that battery up to 100% without any fudge factor.

 

[YurtSolar]

I have the Victron 500 amp smartshunt the ip65 version, I'm not sure if it's the cheaper one or not but it seems to be working well. Length from negative terminal to shunt is 18 inches, longer than I wanted but I have the batteries inside a heated box with the shunt on the outside. Distance from the shunt to the SCC is about 2 feet so pretty close.

 

[sunshine_eggo]

Very helpful, thank you so much @sunshine_eggo ! I don't anticipate using my AC battery charger, but if I do use it sometime should I just change that one setting in the app while I'm using the AC charger and then change it back when I'm back to solar?

No. It will still function properly provided you are also AC charging to the same absorption voltage.

Regardless, triggered syncs on every charge aren't required to maintain accuracy. The shunts can simply count back up to 100% as charging occurs.

Regarding VE.Smart networks:

Smartshunt or BMV-712 with temperature sensor can be used to feed voltage, battery current and temperature data to Smartsolar MPPTs. This improves charging and tends to speed it up a little since it extends the bulk phase of charging by a bit (elimination of charger induced voltage drop). Temperature data can be used to provide low temp charge protection for LFP on the MPPT.

Lastly, networked MPPT tend to stay in the same phase of charging to better distribute the charge load across multiple MPPT. This is most effective in bulk mode. Once in absorption, and particularly in float, the chargers don't generally share current equally.

 

[YurtSolar]

No. It will still function properly provided you are also AC charging to the same absorption voltage.

Regardless, triggered syncs on every charge aren't required to maintain accuracy. The shunts can simply count back up to 100% as charging occurs.

Regarding VE.Smart networks:

Smartshunt or BMV-712 with temperature sensor can be used to feed voltage, battery current and temperature data to Smartsolar MPPTs. This improves charging and tends to speed it up a little since it extends the bulk phase of charging by a bit (elimination of charger induced voltage drop). Temperature data can be used to provide low temp charge protection for LFP on the MPPT.

Lastly, networked MPPT tend to stay in the same phase of charging to better distribute the charge load across multiple MPPT. This is most effective in bulk mode. Once in absorption, and particularly in float, the chargers don't generally share current equally.

Thank you for sharing this knowledge @sunshine_eggo ! This brought up two thoughts.

1. You convinced me to get the temp sensor - I was on the fence but now I see more of the utility with this network communication. I'm going to order that today.

2. My AC charger (which I don't anticipate using much at all) is a Cotek cx2415. It says that it works with lithium, but the lowest charging voltage option is 28.8 followed by a float of 27.0. The 27.0 float is the same as my SCC float setting, but that 28.8 is much higher than the charge setting I have programmed in, which EG4 recommends (28.1). Should I not use the Cotek charger given that it charges with a higher voltage than is recommend? For reference I currently use less than 1kw per day and have 2 batteries in parallel with 10+ kwh total so it's unlikely I will need to use the charger much at all unless my draw increases.

 

[sunshine_eggo]

Thank you for sharing this knowledge @sunshine_eggo ! This brought up two thoughts.

1. You convinced me to get the temp sensor - I was on the fence but now I see more of the utility with this network communication. I'm going to order that today.

2. My AC charger (which I don't anticipate using much at all) is a Cotek cx2415. It says that it works with lithium, but the lowest charging voltage option is 28.8 followed by a float of 27.0. The 27.0 float is the same as my SCC float setting, but that 28.8 is much higher than the charge setting I have programmed in, which EG4 recommends (28.1). Should I not use the Cotek charger given that it charges with a higher voltage than is recommend?

It's fine. That's 3.6V/cell, which is safe for LFP. The BMS will protect the battery if one or more cells exceeds the allowable cell limit.

For reference I currently use less than 1kw per day and have 2 batteries in parallel with 10+ kwh total so it's unlikely I will need to use the charger much at all unless my draw increases.

Nice.

 

[Bananaman321]

It's very heartwarming to know that all you have to do is mention the V word and @sunshine_eggo magically appears

He might as well put a giant V on his eggo

It sure would be nice if he would share some discount codes with us "Leggo-My-Victron-eggo"

 

[sunshine_eggo]

It's very heartwarming to know that all you have to do is mention the V word and @sunshine_eggo magically appears

He might as well put a giant V on his eggo

It sure would be nice if he would share some discount codes with us "Leggo-My-Victron-eggo"

If I had any, I would share. My fanaticism comes with zero financial benefit.

 

[740GLE]

If I had any, I would share. My fanaticism comes with zero financial benefit.

It probably does the actual opposite!!

I know my spending has increased once I tasted the blue koolaid.

 

[Bananaman321]

It probably does the actual opposite!!

I know my spending has increased once I tasted the blue koolaid.

There's always the peace in mind that it will most likely pay it in longevity

 

[robbob2112]