Victron battery voltage confusion

[dhays]

I have a Victron Smart Solar 100/30 MPPT controller connected to a house bank with a Victron Smart Battery Sense battery sensor connected to the same VE Smart Networking network via Bluetooth.

My controller is showing a different battery voltage than my battery sensor. I don't understand why?

No other charge sources at the moment. Engine off. Genset off. Not connected to shore power.

 

[dhays]

FWIW, testing shows that the Battery Sense is sending the correct voltage information.

 

[SteveK]

I get similar WTF readings and have learned to ignore them. I do look for any adjustment to readout to agree with a measurement at battery terminal, but if none found just accept it.
For instance I have two inverters off the same house bank which are 1/10 volt off. I guess I could conclude the one wired 1st in parallels could read higher and the 2nd in line sees a slight lower. SHRUG

 

[Delta Riverat]

I wouldn't worry unless over 5%.

 

[dhays]

I only noticed as I was down at the boat to check on the batteries. My dock pedestal 50a/110v receptacle burned up a week ago and the marina hasn't been able to replace it yet. So I have been relying on solar to keep up with the refrigerator until they can replace it. Good news is that the solar charger got it back to float every day despite the weather being overcast and cloudy the past week.

 

[twistedtree]

Looks like a bug.

 

[dhays]

Looks like a bug.

That is what I was wondering. When connected to the network, shouldn't the MPPT controller display the voltage reading from the battery sensor?

 

[av8r]

It’s possible you are seeing the voltage drop across the wire run from the controller to the battery bank. There will be a drop across the run at 14 amps, it will range from negligible to substantial depending on wire size, length of run, and number of connections.

 

[dhays]

It’s possible you are seeing the voltage drop across the wire run from the controller to the battery bank. There will be a drop across the run at 14 amps, it will range from negligible to substantial depending on wire size, length of run, and number of connections.

I expect there to be a drop along the wire running from the controller to the battery. Typically, before I had the battery sensor networked with the controller, there was a .2v drop along the wire to the battery.

Maybe it is just that I'm wrong as to what I expect? Does the Victron MPPT controller display the networked value of the battery voltage sent by the battery sensor? Or does it display the voltage at the output of the controller? If the latter, why? Is there a way to ensure that the controller is using the battery sensor information to set the charger voltage?

 

[twistedtree]

Is all the software up to date in all the devices? That would be the first step, hoping that it's a bug that has already been fixed.

I would next check to see if the MPPT is operating according to the remote voltage sense, or it's own local voltage sense. It may be that only the MPPT's display is using the local sense voltage, yet the actual operation is correctly using the remote sense voltage. In other words it might just be a display bug, and not an operational issue.

If you have the patience and inclination, you could check Victron's community forum to see if anyone else has reported it, and if not, raise the question.

 

[luna]

If the MPPT is displaying its own local voltage value and not the battery sense value, under a charge current of 14 Amps a voltage drop of 0.36 V is not surprising.
To help confirm that this is actually occurring, you don’t have to do too much.

Simply while enjoying the company of the ones you love and your favourite beverage watch the sun go down, for about the last hour.
As the current falls the voltage value difference should diminish and the 2 voltage values eventually match.

Have a good time during the test!

 

[cafesport]

The Bluetooth remote sensors are accurate for voltage, but the temps are constantly out of whack ( no adjustment possible). They work pretty well with other victron charge sources if the remote sensor is within Bluetooth range and they are networked together using the ve smart network. Your controller should use the remote sensor voltage and temp readings to maintain the charge profile selected at your controller, even though the reported outputs are misreported. You may also notice that individual banks vary quite a bit from the shunt values on your bmv if you have one.

 

[Bmarler]

I have the same discrepancy with my Victron smart solar controllers too. Like has been mentioned, the solar controller is giving a volt reading off of its terminal voltage. Depending on distance to the battery bank, and the wire gauge between the two, and a host of other possible plot complications, there will be slightly different values, especially when the panels are producing max output. Since they’re programmable, you can use the actual battery voltage and adjust the solar output to achieve the value you want.

 

[Bmarler]

The Bluetooth remote sensors are accurate for voltage, but the temps are constantly out of whack ( no adjustment possible). They work pretty well with other victron charge sources if the remote sensor is within Bluetooth range and they are networked together using the ve smart network. Your controller should use the remote sensor voltage and temp readings to maintain the charge profile selected at your controller, even though the reported outputs are misreported. You may also notice that individual banks vary quite a bit from the shunt values on your bmv if you have one.

Can you actually set the solar controller to use the data directly from the remote sensor instead of the local sensor?

 

[dhays]

I have the same discrepancy with my Victron smart solar controllers too. Like has been mentioned, the solar controller is giving a volt reading off of its terminal voltage. Depending on distance to the battery bank, and the wire gauge between the two, and a host of other possible plot complications, there will be slightly different values, especially when the panels are producing max output. Since they’re programmable, you can use the actual battery voltage and adjust the solar output to achieve the value you want.

You may be correct that the controller is displaying the voltage at the terminals for the battery on the controller. However, I am suspicious that the controller is setting the charge parameters by the controllers voltage and not the battery sensor. It seems as if the charger changes to Absorb before the battery sensor reaches the absorb voltage.

 

[Bmarler]

If it uses the terminal voltage, it certainly is switching early. You can program the controller for a higher voltage before switching to absorb.
If you depend on solar for the majority of your charging I would do that. If solar is just used on weekends and maybe a week trip here and there, it’s not as important.

 

[twistedtree]

If it uses the terminal voltage, it certainly is switching early. You can program the controller for a higher voltage before switching to absorb.
If you depend on solar for the majority of your charging I would do that. If solar is just used on weekends and maybe a week trip here and there, it’s not as important.

It's certainly supposed to be using the remote voltage sense. That's the whole point of adding that device, and both that and the MPPT report that they are correctly networked together. So I'd be surprised if charging isn't based on the remote voltage sense since it would be such a blatant bug. But I could definitely see the MPPT reporting (but not acting on) it's locally sensed voltage, either as a bug, or even intentionally so you can see the voltage drop. Somewhere buried in the mass of Victron online info it might even say somewhere who it's supposed to work, but good luck finding it.

 

[SteveK]

I read mppt takes higher voltage and converts it to amps and charges at lesser volts. so incoming pv volts are higher than at bank voltage.

 

[cafesport]

Can you actually set the solar controller to use the data directly from the remote sensor instead of the local sensor?

If you have the long range sensor, and the battery is close enough to the smart controller, the controller will use the data from the remote battery sensor.

The ve smart network page should show what is on the network and whether the data is being used.

 

[cafesport]

I only noticed as I was down at the boat to check on the batteries. My dock pedestal 50a/110v receptacle burned up a week ago and the marina hasn't been able to replace it yet. So I have been relying on solar to keep up with the refrigerator until they can replace it. Good news is that the solar charger got it back to float every day despite the weather being overcast and cloudy the past week.

Using the remote sensor lets you see and compensate for voltage drops down the delivery line.

The remote sensor also logs data for 180 days so you can see exactly what happened to your battery when you lost your shore power.

You will most likely end up creating a custom charge setting using the advanced programming settings on the smart controller.

 

[dhays]

Using the remote sensor lets you see and compensate for voltage drops down the delivery line.

That is what I had been doing until I installed a long range sensor that was able to network with the controller. I then expected the controller to use that voltage and temp information to adjust the current going to the batteries. I am not sure that is happening.

The remote sensor also logs data for 180 days so you can see exactly what happened to your battery when you lost your shore power.

You will most likely end up creating a custom charge setting using the advanced programming settings on the smart controller.

I already setup a custom charge profile for the controller.

Next time I am on the boat I will carefully compare the controller activity with the battery voltage. When I looked the other day, it appeared that the controller went to absorb before the battery reached the absorb voltage.

 

[luna]

After reading what TT wrote I thought I would have a look at "the mass of Victron online info" as I've heard before that it's a large unorganized mess. But first, as usual I looked at the 2 unit's manuals.

First, the Battery Sense gizmo.
Page one, the first 2 lines reveals what the unit is suppose to do.

https://www.victronenergy.com/upload/documents/Smart_Battery_Sense/17801-Smart_Battery_Sense_Manual-pdf-en.pdf

Then the MPPT's manual on page 10 clause 3.11 spells out the behaviour of the MPPT once connected to the Battery Sense device.

https://www.victronenergy.com/upload/documents/Manual_SmartSolar_MPPT_75-10_up_to_100-20/29694-MPPT_solar_charger_manual-pdf-en.pdf

It appears that the MPPT will increase it's voltage by the difference between the Battery's actual voltage as provided by the Battery Sense device and the MPPT's normal output voltage, thereby accounting for voltage drop due to current. It would only make sense that the MPPT displays what it measures as it's output as it can quite happily run without the Battery Sense device.
This also means that the the 2 reported voltage values will always be different until the current drops to zero. Have you tried the sunset test yet?

If it doesn't do this adjust for voltage drop or the MPPT now switches to absorb at a lower voltage than programmed (which I think is your early) and you followed the, when can I and when can't I use the Battery Sense device, plus both unit's are installed correctly, perhaps you have a valid warranty claim.

I never got to the on line Victron forum.

 

[dhays]

Thanks. I think I need to do as you and Cafesport have indicated which is to closely complete more the history of both instruments and look to see what the battery voltage is when it goes from Bulk to Absorb. Since my dock power is still out I will have a couple weeks of data to look at. I will also look at the switch from absorb to float and see what the current is when it makes that change. They both should match what I have entered into the custom charge profile.

Unfortunately, I can't access the data unless I'm on the boat and im currently in the middle of two weeks of work as I fill in for my colleagues vacations.

However, I only have a total of 19 work days left over the span of 121 calendar days till I am completely and permanently retired. So more time for the important boat stuff.

 

[bglad]

I installed LFP batteries that I can Bluetooth with to see what is going on inside them. I noticed my Magnum Energy inverter meter shows a little lower voltage than the battery Bluetooth says. After messing around a bit with the inverter I went to the BMK meter and found it shows the same as the batteries. I assume the difference is caused by the resistance of the BMK shunt.

I adjusted the inverter charging voltage to avoid overcharging the batteries. It is set to charge the batteries at 56 volts but finishes at 55.6 at which point the batteries are 56-volts.

I have a Victron Smart Solar 100/30 MPPT controller connected to a house bank with a Victron Smart Battery Sense battery sensor connected to the same VE Smart Networking network via Bluetooth.

My controller is showing a different battery voltage than my battery sensor. I don't understand why?

No other charge sources at the moment. Engine off. Genset off. Not connected to shore power.

View attachment 157442View attachment 157443View attachment 157444View attachment 157445

 

[Capt Ray]

Confucius say: "Man with two watches never knows what time it is."

Here is a good article on the subject of volt meter accuracy:
https://www.fluke.com/en-us/learn/blog/digital-multimeters/accuracy-precision

Seriously, if you own a good quality volt meter, it would be a "fun" experiment to physically see if that 0.36 difference (delta or voltage drop) was discernable on both ends of the battery cables between the devices.

The other thing to do is watch the delta over time. It is always the same under different loads and charging cycles?

 

[Hobbit]

If the MPPT is displaying its own local voltage value and not the battery sense value, under a charge current of 14 Amps a voltage drop of 0.36 V is not surprising.
To help confirm that this is actually occurring, you don’t have to do too much.

Simply while enjoying the company of the ones you love and your favourite beverage watch the sun go down, for about the last hour.
As the current falls the voltage value difference should diminish and the 2 voltage values eventually match.

Have a good time during the test!

I agree with what you've suggested, with the little experience I have with panels on our motorhome, I'm currently looking into putting 2 to 4 on our boat, our house bank is 32 volt. I'm in contact with Solar Marine Systems and in the process of what might work...or if its even worth it...generator run time is not an issue that bothers us because we can barely hear it....more of a problem when in quiet anchorages. I recently installed Victron BMV 712 battery monitors on our 12 volt and 32 volt systems and really like them.
Cheers Bill