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roy-w avatar image
roy-w asked

Victron MPPT 100/20 Below -30C

I’m using a Victron 100V 20 A MPPT regulator, a 220 W solar panel and three 100 AHr 12V lead acid AGM batteries hooked up in parallel. The load attached to the regulator draws 600mA continuously. The system was working perfectly till we entered a cold snap of 5 days below -30 degrees Celsius (daytime high). During the first night below -30C the load turned off around 10 pm due to low battery voltage. Then the load turned on around 9 am the next morning. This repeated the next 4 nights with the load turning off earlier each night. I downloaded the regulator history and noticed that the maximum absorption charging voltage was only 14 V when the temperatures were below -30C. Just before the cold snap the absorption charge voltage would go up to 15.09V. The manual for the Victron regulator shows a graph which indicates that below -30C the charging voltages drop when they should go higher as per lead acid battery charging characteristics. Basically the lower charging voltage does not fully charge the battery at the these low temperatures. Has anyone else noticed this, if so is there a fix for this problem?


battery charginglead-acidtemperature compensation
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Alexandra avatar image Alexandra ♦ commented ·

@Roy W

Have you set the temp compensation correctly for your battery? Is the battery supposed to be charges so cold or do you have heating pads?

Do you have enough solar to be reaching full charge, maybe that is insufficient?

The temps could be dropping out of mppt working range?

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roy-w avatar image roy-w Alexandra ♦ commented ·
Hi, thanks for your suggestion. I have selected the proper battery (AGM lead acid) and the temperature compensation is setup properly. I found an article from Victron stating that below -30C the temperature compensation turns off and the charge voltages returns to “normal values” which are the values for +25C. So Victron engineers decided to give up below -30C. I am using their regulator at a remote unmanned data collection site. A warning to anyone in a cold climate, stay away from Victron regulator.


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Alexandra avatar image Alexandra ♦ roy-w commented ·
In the datasheet the working range is given to -30. So no secret there. It is an electronics limit more than anything else.
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roy-w avatar image roy-w Alexandra ♦ commented ·
The regulator still works below -30C, the engineers chose to turn off the temperature compensation below - 30C. I have used many type of electronics that were specified to work only to zero degrees C and they work down to minus 40C.
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nesswill avatar image nesswill commented ·

@Roy W

as Alexandra says, this is how mine is set but you MUST check with the battery manufactory to ensure correct settings...

temp-comp-12v.jpg

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nesswill avatar image nesswill commented ·

Hi @Roy W out of interest.

What temp are the batteries at? (and the MPPT -30 is it max low temp) i ask because AGM Voltage will drop in cold temps.

With your 600mA does this include all equipment attached to the batteries, if not you could be drawing more that you realise, do you have a SmartShunt in the system?

And as @Alexandra says,

Do you have enough solar to be reaching full charge, maybe that is insufficient?

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roy-w avatar image roy-w nesswill commented ·
I have verified that the load is 600mA by using a multimeter. The batteries were lower than -30C. We had temps of -40C. All lead acid battery including AGMs require a higher voltage when the temperature goes lower. I have a 220W bi-facial solar panel. Plenty of solar power.
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nesswill avatar image nesswill roy-w commented ·

@Roy W Thanks.

Hi correct on the higher charge voltage when cold but what does the spec sheet say on the batteries as mine are only rated to -20c.

No SmartShunt then?

Can you post you solar history, something like this below? it will help us to help you.

logf.jpg

EDIT.

I suspect the MPPT is just turning off due to the low temps, a picture like above might confirm this.

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logf.jpg (117.2 KiB)
3 Answers
kevgermany avatar image
kevgermany answered ·

Might be worth checking the MPPT stats, particularly output current. As sad, you might have insufficient solar for these conditions, even with such a light load. Although the MPPT will compensate for temperature, if there's a low charge rate and partially depleted batteries, the voltage won't be high.

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roy-w avatar image roy-w commented ·
Thanks for your suggestion. I have looked at the MPPT Stats and there is an obvious drop in charging voltage when the outside temperature is below -30C. I found a reference article from Victron that stated that the temperature compensation algorithm turns off below -30C and the charging voltage returns to ”normal values” which are the ones at +25C.
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kevgermany avatar image kevgermany ♦♦ roy-w commented ·
I seem to remember reading that, now you mention it.
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klim8skeptic avatar image
klim8skeptic answered ·

@Roy W One option would be to turn temp compensation off.

Then calculate the absorp and float voltages for your batteries when they are at -30c.

Dont forget to revert to temp compensation when the batteries return to manageable temps.

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Justin Cook avatar image
Justin Cook answered ·

To be fair, below -30C is outside the published operating range of the MPPT entirely, so I'm mostly just impressed it continued functioning at all. Good on you, Victron!

temp.png


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