BMS allowing a charge in below freezing temps

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dapple asked Jan 20, '24

BMS allowing a charge in below freezing temps

Hello,

I have a question on a setup from 2020. With the single digit temps in the Midwest I think I may have found a weakness in my system that has otherwise performed flawlessly. I noticed that my battery is accepting a charge even in below freezing conditions. I was told that the BMS would not allow a charge, but that information appears to be wrong. My system consists of 2 -200 amp Victron smart batteries, ve.bus BMS V1, BMV 712, and a MPPT 100/50. The BMV closes the relay at 45 degrees F to 2 small heating pads (one for each battery) and the battery has the under temperature alarm set to the suggested 41 degrees Fahrenheit via the Victron app. Additionally the batteries will charge via the alternator when the van is running. My questions are as follows

-Does the BMS v1 allow a small charge below freezing conditions or should it be stopping the charge entirely

-When the smart battery is under the SL-22 Under Temp alarm and states “Charging disabled” is it supposed to not allow a charge or is that up to the BMS

-Is there a way to stop charging with my system (it seems like I have exhausted the options)

-Does anyone have a suggestion to larger heating pads that could possibly keep the batteries above freezing

-Would adding a smart dongle to my Freedom X invertor give me the ability to turn off charging (from shore power, alternator power, and Solar) when the batteries are below freezing

-Any advice is more than welcome.

Here is a pic of the last below freezing event trend from the BMV. I unplugged the shore power as soon as I noticed this.

BMS

bmv.jpg (158.6 KiB)

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regman54 commented · Jan 20 at 05:41 PM

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Answer 1 · 2024-01-20T16:25:35Z

Matthias Lange - DE answered · Jan 20 at 04:25 PM

Did you connect all charging sources to the "charge disconnect" of the BMS as shown in the manual?

Do you have a wiring diagram?

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Answer 2 · 2024-01-20T16:58:49Z

dapple answered · Jan 20 at 04:58 PM

Thanks for the reply. I didn't do the build out in the Van. I had a very reputable company do it and I was told at the time of the build that the BMS would control the under temp charging parameters. For purposes of this question I would be 99.9% certain that yes, the charge disconnect would have been utilized.

After seeing the battery charge in freezing temps I did a deep dive into research. My research indicated that the V1 BMS only disconnects in over temperature situations. Should it be disconnecting in under temperature situations as well?

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