I came across this blog entry which basically says that, for lead acid batteries, lower temperatures require higher charging voltage. Can anyone please explain why this is true, or point to an authoritative source?

I did ask this question on Chemistry SE a while ago, and those guys seem to be of the opposite opinion: higher temps need higher voltage.

Intuitively I disagree with them and agree with the blog post: lower temps need more power to move molecules around, remove sulphate crystals etc. But I seek a definitive authoritative explanation.

Hallo,

ich bin neu hier und hätte eine Frage an Euch...

Ich habe einen MPPT Smart Solar 100/50 und habe diesen heute mit 4 12V 140Ah AGM Batterien (Electronics GmbH)

verbunden (je 2 in Reihe und parallel -> 280Ah 24V).

Bei der Inbetriebnahme des Ladereglers habe ich die Daten von meinen Batterien eingegeben (eigentlich nur die Schlussspannung 28,8V. Im Datenblatt steht Ladekennlinie AGM1 mit Schlussspannung 14,4V).

Es ist auch ein Smart Battery Sens verbaut, der die Spannung und Temperatur an den Laderegler meldet.

Bei der Eingabe vom Temperaturkorrekturfaktor habe ich jedoch ein Problem... hier kann ich nur bis -60mV gehen.

Auf dem Datenblatt der Batterie steht aber (max. Ladespannung 14,5V empfohlen):

Das wären aber 216mV für die 2 in Reihe geschalteten Batterien (je 6Zellen)... oder habe ich hier einen Denkfehler?

Und wo kann ich die im Datenblatt max. empfohlene Ladespannung einstellen?

Bin hierbei für Jede Hilfe/Info Dankbar!

Mit freundlichen Grüßen, Richard.

With a simple system, all DC without inverter but with a GX device + MPPT + smartshunt with temp. sensor and GEL batteries, which is the correct way to compensate temperature?

a) Enable BLE smart.network and join MPPT and smartshunt; or

b) Enable DVCC on GX device and select Smartshunt as the Battery monitor/ temperarture sensor

Or... both (not at same time) work?

I recently installed 28kw of lithium batteries in a bus conversion and we'll hit colder temperatures in central MN USA.

It is my understanding that it's no so much that lithium can not be absolutely charged below freezing but that it must be derated or compensated below 45f or so. This is because the negative ions stack up and can damage the cells of charged too quickly.

I have an idea... what if we set a temp compensation value intended for lead acid batteries was reversed? Example, I think a traditional value would be -36mV/C, but what if that value was reversed to be +36mV/C or higher. Wouldn't this invert the voltage compensation curve to produce a higher voltage as it got warmer and a lower voltage as it gets colder?

I'm just looking for a way to gradually derate the charge curve instead of a hard off or on switch. I'm also aware of a super secret "Low temperature charge current" setting HEX-Protocol in VE Direct. Would be nice to see that exposed behind a password or something.

Any chance getting the Orion Smart TR DC-DC chargers working with the VE remote battery sensor is happening yet?

i need set up the compensation thing ,i have a 48 volt lithium leaf volt batts,, its at -36.00mV/f, i don't want to hurt or blowup something,, please help,, right now i have the switch turned off

I found out that the temperature compensation does not work correctly. It is too high by a factor of 6! I tried out some things and found out that I need to enter the compensation value per cell and NOT per battery bank as the app is asking for.

Test situation:

• The manufacturer of the used lead acid batteries prescribes a compensation value of -4mV/°K per cell.
• I have 6 cells, thus I use the MPPT controller at 12V.
• The floating voltage is set at 13.36V and the controller is in floating mode.
• Temperature and battery voltage is measured directly at the battery through a BMV-712 battery monitor and send to the MPPT via bluetooth. They are interconnected with each other (which is a pretty cool feature anyway).

The app is asking the temperature compensating coefficient explicitly as per bank and not per cell.

Thus I multiplied the -4mV/°K per cell by 6 and get -24.00mV/°K per bank which I entered in the app.

Today the battery temperature was measured at 19°C. This is 1°C below 20°C (20°C means no compensation).

Expected result:

13.36V + (19°C - 20°C) * -0.024V = 13,384V

Observed result:

13,50V (which is obviously too high for a lousy delta of 1°K)

Then I entered the coefficient as per cell (-4.00mV/°K) and got 13,39V which is what I wanted all the time but never got.

For testing, I also tried to switch off the compensation and got exactly the configured 13.36V.

It looks like the controller is multiplying the entered value internally by 6 as it knows I am using the controller at 12V with lead acid cells (can only be 6 cells as 12V / 2V = 6).

Because of this I killed my new bank last winter as the voltage was too high all the time!!!

Example:

0°C in winter means (0°C - 20°C) * (-0.024V * 6 [6 because of the bug]) compensation

= -20 * -0.144V = 2.88V (WTF?!?)

=>

Floating voltage: 13.36V + 2.88V = 16.24V

Absorbing voltage: 14.40V + 2.88V = 17.28V

Balancing voltage: 15.10V + 2.88V = 17.98V

BTW:

I updated the MPPT to FW v1.50 today which has still the same bug. :-(

Did anyone noticed the same?

Dear all,

The manufacturer of my AGM battery recommends a temperature compensation of -4mV per Cell around 25°C. However it looks like that the neutral point for the victron MPPT is set at 20°C. Is theres a way to adapt this temperature compensation point?

Thanks in advance!

Florian

Hi all,

i'am using a SmartSolar MPPT 100/30 with firmware 1.54 and a external ve.net temperature sensor.

When setting the temp. compensation to -30mV, on temperature below 25c, in my case 18c, the voltage is lowered from 29,4V to ~29,25V instead of 29,55V.

When setting the compensation to 30mV (plus) it works as expected.

Is this a bug?

Thanks so far

Marco

Hello,

Hoping to receive some advice as to how to set the temperature compensation value for my 100/20 controller.

I have 300ah of type 1 AGM, and temperatures constantly shifting around as they are in my converted camper.

The setting is currently sitting on -16.20mV/C.

I have my absorption on 14.6 and float on 13.8.

I will buy a temperature sensor at some point, but for now I'd like some basic advice on how to set the temperature compensation.

I'm aware the MPPT takes a reading, heard it was when idle for an hour or once in the morning and sets it for the whole day.

My controller sits right near my batteries. Currently the temperature goes between a little below minus, and 3 or 4C.

I could place a temperature sensor in my battery compartment that I can manually read from inside my camper living area. With that I thought I can keep an eye on the temperatures and adjust the setting accordingly. But it would be nice to have a basic guide for doing that. Anything like that around?

Many thanks!

I have BMV-702 with temperature sensor together with LiFePo4
I usually use SOC between 95% -60%, to open / close relay, which starts charging at 60% and closes at 95%
Now I also want to close the charge below 0 degrees and test "High temp relay", but it does not work if I simultaneously use SOC.
Do you have any suggestions that will make both controls of the relay work

I have a customer who has six 6V batteries in series/parallel in a 12v system. The customer's battery spec is showing ±3 mV/°C/cell. He is setting up a 12V Multi in Victron Connect and needs the correct value for his batteries. The default is showing -16.20mV/°C.

I'm using the same math that was presented in https://community.victronenergy.com/questions/28107/temperature-compensation-1.html.

A 6V battery is +/-(3cells x 3mV) = +/- 9mV per battery

So for Six 6V batteries in series/parallel would be 6 X 9mV= - 54mV/°C, correct?

Does it matter whether in series or parallel or is it the total number of batteries?

Thanks for the help!

Hello,

I have 2 brand new AGM supercycle controlled by a Tristar TS-60 in diversion mode (Windmill + solar).

I want to set the temperature compensation in the controller, but I didn't find any data in the one page datasheet of the supercycle batteries.

Could you tell me the median temp for no temp modulation (I used usually for flooded or gel 20°C or 25°C) and the Temperature Compensation (default in controller -0.030 volts)

The batteries does not seems to charge easily (very often in bulk, need very strong power to get in absorption and float), but with the same charging power I successfully used for 8 years 2x victron Gel...and I suspect temperature comp. to be badly set for theses new batteries.

Thank you

Olivier

Having trouble interpreting the output of VictronConnect

Components/parameters:

• Smart SCC 150/100
• Smart Battery Sense networked with SCC
• Quattro 5K/48
• Color Control GX
• 48V Trojan battery bank, 58.8V absorption

Remote monitoring via VRM, VictronConnect on PC.

Trojan says -5mV/°C/cell

24 cells

24*5 = -120mV/°C

I can directly see the Smart Sense when local and able to access it on bluetooth. I do not see that I have a way to access it directly via VRM.

I entered -120mV/°C in temperature while it was at the uncompensated absorption level. Voltage immediately increased about 1V as expected based on 34°C, and it didn't seem to be adjusting current to lower it. Shocked me a bit, so I flipped the sign and immediately saw a lower voltage. Head melted, and I just turned it off.

Questions:

1. Does temperature compensation adjust the measured voltage and make it read higher for °C above 25°C?
2. If #1 yes, had I been patient and given the SCC more time, would I have seen the current reduce and the voltage settle to the absorption voltage?
3. When I connect to the SCC, is the temperature reported in the app/PC VictronConnect (PC version shown below) from the networked smart sense or the SCC internal temp?
4. If not the smart sense, is there a way I can see the smart sense via VRM?

[image]

Thanks!

Pretty sure this was asked a few years ago but wondering if anything has changed...

Any chance of VE.Smart Network coming available to the Blue Smart IP67 chargers?

Could really use that actual Battery Temperature reading...on these cool sunny days right now the ambient temp of the charger outside in the shade and the temp of the battery in a black plastic box is quite a big spread after a big charge (88f vs 61f - I think..the Blue Smart doesn't actually show temp- Another feature request to display Blue Smart temp?)

This leaves the MPPT on the VE.Smart Network to think that we are overcharging because it has temp compensated the voltage down for the warm battery (its probably right) while the BlueSmart IP67 is doing the opposite and temp compensating up for the cool charger.

I recently got my MPPT + BMV w/ Temp Sensor configured to match my battery specs. Some are:

• Abs Voltage: 15.00V
• Temp Compensation: -37.8 mV/*C
• High Voltage Alarm: 15.3V
  • Conservatively set...I think 16V is the operating limit of most of my 12V devices

Its winter here and it's bright(ish) but cool today in Michigan (33*F)... I noticed my High Voltage alarm had triggered and it was Abs charging at 15.5V off the panel!

I thought something was wrong and then realized that Temp Compensation is likely the culprit. Did some math and sure enough, I hadn't considered what Temp Comp will do at our frequently low temps.

I'm ok with the temp comp doing its job, but what worries me is that through some math I've determined if the temp drops below 20*F and the sun comes out, it will be ABS charging at 16.0V and I'm in danger of frying a device!

Is it possible to set a max voltage in the MPPT that it's not allowed to exceed no matter what the compensation computes to? It's not uncommon for temperatures to reach 0* here when its clear skies. That would be 16.6V output!

Or..do I need to add a voltage regulator before house loads to prevent from frying my electronics during Abs charge??

Edit: Should also add that this is a lead-acid battery so I should be good to charge down to -4*F but that would be an Abs charge voltage of 16.5V!

Having 3 new 200Ah-a batteries in parallel configuration I'm wondering why their temperature readings and offset are so different :

temp. Offset

No1. 21. 2

No2. 16. 0

No3. 20. 3

Something wrong?

I have a max charge voltage setting on my charge controller . I have temp compensation set up at -4mv per cell as per the data sheet . Is there a max charge voltage the batteries will take when very cold ? I note the Absorption range is up to 14.6volt or 14.9 volt fast charge , should 14.9v be the highest even at low temperatures of 5 degrees and under ? or does it not matter and I should set at 15.5 v or something ?

Hi all,

I have installed EasySolar 48/3000/35-50 and I wonder can my system use battery temperature information from MultiPlus battery sensor for battery temperature compensation on it's MPPT 150/70 if I enable DVCC function on CCGX?

Thanks for your help.

I have 2 Trojan T105 6v connected for 12v. BlueSolar MPPT 75/15. The controller was automatically set at -29.5mV/F. I live in Phoenix, AZ where temps are often 100+F. However, this is for a Travel Trailer, which will be used in much cooler temps 30-80F.

I am was concerned about my charger not reaching the float voltage. I think it's related to the Temp Comp. I'm wondering if this is what's going on. Charger is currently on Float @ 13.2v. Float is set at 13.5v. I live in AZ, current temps are 95-100F. Temp comp is set at -29.5mV/F. My Absorption is set at 14.83v. My history shows a max of 14.58v for the last 3 days. There has been a day that was 13, and another that was 14.83v. But 14.58v is the most consistent reading.

So I think my math correct on this?

13.2 + 0.295 = 13.5.

14.58 + 0.295 = 14.875

That said, the data sheet says subtract 0.0028v per cell, per degree above 77F. 0.0028 x 6 cells = 0.0168v. Easy math, temp was about 87f at dawn. So 10 x 0.0169 = 0.169. So wouldn't the correct setting be -16.9mV/F? The data sheet also says to ADD 0.0028v per degree below 77F. If the temp at dawn is 37F, shouldn't the Temp Comp be set at 67.6mV/F?

Am I supposed to calculate and set the Temp Compensation each time I go camping for the current weather? Or am I just supposed to set it at one setting and the controller will adjust accordingly?

My Crown batteries have a temp compensation coefficient of 3mV/°C. My mppt ‘wants’ the value in °F.

What is the conversion if any? I found this example but the math is not logical to me.

For temperatures below 25°C, adjust +0.005VPC/°C (or 0.003VPC per ̊F). For temperatures above 25°C, adjust -0.005VPC/°C (or 0.003VPC per ̊F)

I bought Victron MPPT 100/50, BMV 702, Lithium SuperPack 768Wh, and even Victron solar panels. All of it because of the great community support and the ability to read status & control those devices without using manufacturer software.

Unfortunately, VE.Direct HEX Protocol MPPT whitepaper rev. 10 (latest) is promising a feature that does not work: the Remote control registers section (p. 18 and p. 20) states that it is possible to upload battery voltage and temperature to a MPPT (from a BMV). Well, this morning in Darmstadt, Germany my MPPT was happily full-blown bulk-charging the Lithium while the battery temperature was 4deg C. According to Victron SuperPack specs this is below the authorized level. All this in spite of a Python script constantly uploading BMV battery voltage and temperature to the MPPT.

Question (supplication...): can the Remote control registers section in HEX MPPT whitepaper be further clarified regarding the Battery voltage & temperature sense commands, their expected response (currently I'm getting "1"), and whether it is necessary to modify the MPPT Network mode to make them work?

I have an Easysolar 48/5000/70-100 with CGX and seperate BMV 702.

I notice that there is an installed battery temperature sensor to the EasySolar, and I assume that is part of the charger (it is not the optional BMV one). I would like to know if it is possible to configure the system so that that temperature information feeds the BMV state-of-charge calculation?

Hi,

While charging lithium batteries, using the lithium setting. What effect does the temperature compensation have?

I.e. reduce charge current belwo 5 degrees for example?

Matt

Hi
Just bought the SmartSolar MPPT250/85 (SCC125085210) along with a Smart battery sense when I came by an article stating that the devices are incompatible:

https://www.victronenergy.com/live/victronconnect:ve-smart-networking

Bummer.

1. Can/will the charger become compatible with the VE.smart networing and the Smart Battery Sense through a future firmware update, or is this a hardware issue?
2. On a system with a CCGX and BMV 702/712, can the SmartSolar charger voltage compensate from the temperature data on the BMV, that should be available on the VE.bus? DVCC?

Hi team,

Seeking optimal setup for solar charging and ensuring live Volt and Temp values are used during charge cycle.

I understand the BlueSolar will use internal temp sense for baseline just prior to start of day charging. Can the MPPT use the temperature sensor on the 702 for live input during charge cycle to compensate from temperature.

Additionally can the MPPT source voltage at SHUNT on 702 to more actual gauge the votage level at the battery specifically rather that at the MPPT. (I have noted a differance from what the MPPT show as voltage vs what the 702 shows as voltage at the battery by 0.5VDC. The distance between MPPT and SHUNT/Temp Sensor is cable length POS of 5-6 meters plus return of same distanace for NEG. Cable gauge is 70mm2, so I don't believe differance is due to voltage drop over cable length?)

There are 2 x MPPTs and 2 x 702 are connected to VenusGX. I am currently running 702 with temp sensor, but in future would like to move to midpoint monitoring on 702 and use alternative battery temp sensor conneced to VenusGX for use by the MPPTs

Thank you.

Hello

I have the trouble to set the correct temperature correction value for a bluesolar ( firmware 1.16) 100/50. I have a 24v battery bank with two of this 12V batteries in serie. The manual indicates -30mv/K temperature correction for the cycle use.

Is it correct that in my case with 2x12V batteries = 24V bank I have to set the temperature correction to 2*-30mv/K = -60 mv/K?

The bluesolar doesn't accept the -60mv/K temperature correction value.

Is my calculation bad?

Thanks

p.s Sorry guys there is the link for the battery manual: https://www.apb-energy.fr/site/medias/batterie-solaire/UCG200-12.pdf

Batteries.pdf

According to the battery profile document attached, what should be my temperature compensation setting for 2 x 6 volts wired in series? I have an SmartSolar MPPT 100-50.

Thanks!

Hi All,

I have 2 x 150/70 Bluesolar charge controllers VE.can connected, so settings are only available to edit via the LCD. I am trying to rescue a sulphated battery bank -and as a result I wanted to turn off the adaptive setting in the menu but I only seem to get an hrs value of 1-8. Is there somewhere else I can change this - I was looking for some setting that says 'fixed' .

I also wanted to set the temp compensation to 5mV/C but seems like the max is 3.5 and default is -2.7mV/c. any one out there able to help ?

Thanks in advance.