Ideas for the definitions for these Schneider equipment settings

[pvdude]

I can’t find any definitions for these Schneider settings in the FAQ’s here.

Schneider tech support says these values have to match in my Inverter, MPPT controller,
and Battery Monitor, as all are connected by XANBUS.
(Looks like no one told the Battery Monitor team about this.)

Guesses welcomed as to what these mean, and for my location, the average temp where the batteries are located is about 80-85˚f most of the year.
Slightly less in Winter (both days).
All devices are at the latest firmware level.

Schneider Battery Monitor
Temperature Coefficient in Ah/˚C default is 0.7
Peukert Exponent default is 1.25
(note: Victron has a really good explanation of this variable, which I read over a few times.
After regaining consciousness, I have decided not to adjust it.)

8. Battery capacity and Peukert exponent

www.victronenergy.com

Schneider 100A-600vdc MPPT charge controller
Battery Temperature Coefficient -90mV/˚C

Schneider XW Pro+ inverter
Battery Temperature Coefficient -90mV/˚C

The main problem seems to be that the Battery Monitor Temperature Coefficent and the other Schneider equipment Temperature Coefficent terms are not compatible. How does one correlate Temperature Coefficient in Ah/˚C with Battery Temperature Coefficient in mV/˚C.
Femto-Newtons per Parsec?

 

[Horsefly]

The Peukert exponent of 1.25 is about right for lead acid batteries. Not sure what the temperature coefficient is.

 

[GVSolar]

I believe you have Rolls Batteries... I would talk to them and let them do the math - and double check the other settings.

 

[pvdude]

I tried that, Rolls tech support told me to set the Battery Temperature Coefficient to 120mV/C, Schneider tech support told me to set the Battery Temperature Coefficient to -80mV/C.
Flip a coin? (I went w/ the Schneider value, because they asked me specifically what the typical temperature is here, Rolls did not)

 

[GVSolar]

Wise man. Go with the girl that brung you.

 

[Horsefly]

I tried that, Rolls tech support told me to set the Battery Temperature Coefficient to 120mV/C, Schneider tech support told me to set the Battery Temperature Coefficient to -80mV/C.
Flip a coin? (I went w/ the Schneider value, because they asked me specifically what the typical temperature is here, Rolls did not)

I think you are getting your temperature coefficients mixed up. For charging lead acid, you have to increase the charge voltage as the temp goes down. That coefficient is some negative mV per °C, and that's the two numbers you got from Rolls and Schneider (I'm sure there was supposed to be a negative sign on the number from Rolls). Your battery monitor wants a different coefficient, according to what you posted: Ah/°C. Your battery monitor obviously isn't adjusting a charge voltage, so don't use the charging temperature coefficient.

My guess is that the battery monitor somehow adjusts the battery capacity based on temperature, but I'm not sure that makes sense.

 

[pvdude]

I guessed that the Rolls number should be negative, but as I am learning about solar, assume very little.
Here is what Rolls sent me.
Also do not understand why they would not want the actual 445Ah rating of the batteries used.

 

[Horsefly]

Yeah, for sure that temp coefficient is to compensate the charging voltage according to temperature. I know that screen in the SCP, and I guess I forgot that they don't use a negative sign, but charging temperature coefficients are always negative. You would never be charging at a higher voltage as the temperature goes up.

I can't speak much about your XW Pro and MPPT100-600, but on my SW4024 and MPPT60-150 the reason you have to fake that your battery is smaller than it's actual size is because Schneider doesn't allow you to adjust the absorption tail current. It is hard coded for .02C. So if you put in 440Ah for the size, they will end absorption at 2% of 440Ah, or 8.8A. By telling the equipment that the size of the battery is actually 325Ah, the absorption tail current will be 2% of 325Ah, or 6.5A. I've heard some experts complain about Schneider not allowing the tail current to be set manually, and most think that 2% is too high. Anyway, that could be one explanation for the fake capacity setting.

 

[GVSolar]

What Horsefly said. (especially the 2% part - that's how you set the tail current)
One of the nice things about LFP is they don't use temperature compensation.
I skipped the Schneider Battery Monitor altogether, as it is relatively useless unless you have a Xanbus enabled battery (like the Discover AES units - but $6k, sheesh). I went with the Thornwave Powermon battery monitor - bluetooth, coulomb counting, SOC and can fire a relay... 119-159 bucks. Works great.

 

[pvdude]

Great info! I made the config change.
As a new solar DIY guy, I did not know anything, so I just checked all the boxes and put the pile's o parts together.
I can see now that the Battery Monitor and SCP are not too usefull.

Here is what Schneider told me about the BM, not sure why this is important?:

 

[Horsefly]

The battery monitor is not very useful (in my opinion) but the SCP is pretty critical.

Here is what Schneider told me about the BM, not sure why this is important?:

They are just saying that using the voltage to get an SoC is pretty worthless, and the BM is at least trying to do bettery.

Like @GVSolar said, a Coulomb counter like the Victron Smart Shunt or the Thornwave Labs powermon (and actually, several pretty cheap devices from China) is better to tell you what your SoC is.

 

[GVSolar]

Yep. SCP is a must, good to have buttons if the Gateway or Combox lose their mojo. And they can. I use the "live" Combox graphics (similar to Gateway) along with the Thornwave SOC for system monitoring