question

wayne avatar image
wayne asked

100/50 MPPT solar controller does not use the VE.smart networking voltage to switch to absorption

I have a BMV712 Smart with thermocouple attached which is transmitting voltage and temp to a 100/50 Solar controller using the VE.smart network. The solar controller shows the same volts and temp as the 712, when monitoring via bluetooth, however, the controller switches to absorption on reaching the MPPT's output voltage and not the battery voltage as displayed on the BMV and also on the MPPT bluetooth screen. Therefore, the volts lost in the controller to battery cable are not compensated for and the battery does not reach full charge. Any help with this is appreciated.

MPPT Controllers
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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi @Wayne, good news: today we released v1.41 for the MPPTs, which includes a fix for this.

More information here: https://community.victronenergy.com/articles/17669/mppt-firmware-version-v141-released.html

Thank you again for bringing this one up.

To get any future readers to the right place quickly, I'll unaccept my previous answer and accept this one instead.

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wayne avatar image wayne commented ·

Fantastic, thank you mvader and Victron team. We are travelling in remote areas in Australia for next couple of weeks. Will load version 1.41 when we get back home. Thanks again!

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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi Wayne, thanks for reporting. I’ve passed this onto R&D and will let you know what they find.

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wayne avatar image wayne commented ·

Thanks mvader. Pls see details of products used attached in screenshots.products being used attached.

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Mark avatar image
Mark answered ·

Just out of interest, how did you confirm this behaviour?

Is it because the indicated voltage during absorption phase (or at the time of switch from bulk phase) is lower than the absorption voltage you have set?

If so, is it simply possible that the battery temperature is >25°C at the time, so the 'compensated' voltage is lower than what you have set? (As it correctly should be)

To test maybe you could temperarily set the temperate compensation coefficient to 0mV/°C to disable it.

Just a thought...

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wayne avatar image wayne commented ·

Mark, thanks for your suggestion. The temp compensation is disabled on the controller.

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Mark avatar image Mark ♦♦ wayne commented ·

No worries.

So do you mean that it has always been disabled, so there is no chance that the behaviour is due to this?

Or have you just disabled it now to test?

I ask because I find it strage to have a BMV-712 with temperature probe connected & linked - but the temperature compensation of charge voltage not utilised...

So how did you disable it - by setting the coefficient to 0mV/°C?


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wayne avatar image wayne Mark ♦♦ commented ·

Hi Mark, the temp compensation was disabled by using the disable toggle via bluetooth. Only use the temp probe to control charging below 5 deg and over 40 deg, not to compensate over full temp range. At reasonably high current, say 35A, i noticed the MPPT switching to absorb about 0.3V prior to reaching the absorb voltage setting. The absorb time set as 1 min. Tonight i noticed one cell bolt was slightly loose. Tightening this reduced the early switching to 0.2V.. further experimenting , albeit at lower charge current has me a bit confused. I set the absorb time to 15min and noticed the controller went to absorb at a lower than set voltage but the voltage climbed during the absorb phase? It looks like the controller may be switching to absorb early AND the controller may not be using the BMV voltage to compensate for cable volt loss at high currents???

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Mark avatar image Mark ♦♦ wayne commented ·

OK - so now I guess that your using a Lithium battery & the Lithium chaging preset in the MPPT?

FYI the 'toggle switch' to disable temperature compensation only comes up if you select the Lithium battery preset. Normally you can only turn it off by using 0mV/°C for the coefficient.

I don't think it will help but maybe also try to enable it then set it to 0, just in case the switch is being ignored for some reason.

What are your observations based on - the Victron connect reading of the MPPT battery voltage?

And I think you said that it matches the BMV? (Proving that it's using the BMV data)

How far away from each other are the 2 devices? Is there a chance that the Bluetooth link is unstable?

Regarding the end of absorption phase:

1- The time you enter is NOT absolute. It is a max time that is used to calculate the 'actual' max absoption time for each charge cycle, based on battery voltage at the time of startup. This is so batteries that have not been fully depleted each day/night are not overcharged by a repeated/unnecessary full absorption charge every day.

Refer to the online Victron Connect MPPT manual for the related table/calculation.

2- If the battery charge current drops below 1 or 2A (depending on the MPPT model) then the battery is considered fully charged and that condition will also end the absorption phase independently. So also keep an eye on this.

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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi both, I can confirm that there is indeed an issue with this; causing the device to start showing Absorption a little bit early; before the voltage stops rising. We were about to start testing a new version; and the fix for this will be included in it. Thank you very much for raising this @Wayne !

And Mark for double checking the temperature compensation and such. Temperature compensation is often forgotten in cases like this.

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wayne avatar image wayne commented ·

Hi mvader, thank you and you team for investigating this. Look forward to a fix!

It is great to have this support for Victron products!! Well done.

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wayne avatar image wayne commented ·

Hi mvader , do you know how the fix for this issue is progressing please?

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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ wayne commented ·

Hi, its being tested as a new version together with many other improvements. Its hard to give a date. Can be only a few weeks; or much longer.

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wayne avatar image wayne mvader (Victron Energy) ♦♦ commented ·

Ok, thanks mvader. Any chance of letting us know when the beta version is available please?

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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ wayne commented ·

Hi Wayne, I'll try to do that. But we don't really have a procedure for that.

You can do it youself by monitoring this page, for VictronConnect betas:

https://www.victronenergy.com/live/victronconnect:beta

The new MPPT firmware will be shipped first as a part of a VictronConnect beta version.

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