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Temp sensor for BMV-712 or not?

rhynorhyno Member Posts: 393
edited December 2020 in Modifications & Upgrades
We bought a BMV-712 for our Tab that's on order to monitor our dual AGM batteries. I saw this note regarding the ~$20 add-on temp sensor. Is the temp sensor worth the tradeoff or should we skip it?  
  • "When using the temperature sensor, the second battery voltage and midpoint voltage monitoring are not available"
Wouldn't the two batteries wired in series have close to the same voltage if identical brand, model and age?
2021 T@B 400 BD, 2021 Lexus GX 460, Kansas City MO
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    HoriganHorigan Member Posts: 611
    edited December 2020
    If you're installing the shunt next to the battery/battery box and in the same temperature environment, I don't think the temp sensor is necessary. 

    Same goes for two six volt batteries in series.  They are in the same box/environment, so monitoring one would be sufficient, if you felt you needed to monitor the battery temp.  If the shunt is nearby, I don't think it's necessary.
    Rich
    2019 T@b 400
    2013 Toyota Highlander 3.5L V6
    Bellingham WA
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    rhynorhyno Member Posts: 393
    Thanks for the tip @Horigan. We will be installing the shunt in the battery box. 
    2021 T@B 400 BD, 2021 Lexus GX 460, Kansas City MO
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    crampshawcrampshaw Member Posts: 16
    Rhyno, if you have a Victron Bluetooth enabled solar controller, the battery temperature measured by the BMV-712 can be transmitted to the solar controller so it can tailor the charging profile to the temp of the battery. 
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    rhynorhyno Member Posts: 393
    edited January 2021
    @crampshaw I had been trying to figure out which would be more important to optimize charging - the battery temperature or the midpoint/2nd battery voltage. From what I am reading online it appears to be the latter.
    2021 T@B 400 BD, 2021 Lexus GX 460, Kansas City MO
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    Denny16Denny16 Member Posts: 5,445
    If you have two 6VDC batts in series, then I would do the midpoint monitoring also.  I have a single 12VDC AGM, so went with the temp sensor.
    cheers
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    crampshawcrampshaw Member Posts: 16
    I choose to monitor temperature since it’s used every charge cycle to optimize the voltage curve. Mid-point voltage monitoring will not optimize anything but watches for a problem in two halves of a better bank. In a battery bank of two batteries of same manufacturer, model, and manufacture date, this problem is unlikely to occur until late in the life of the batteries or in case of abuse. In either of these cases, I’ll measure the mid-point voltage directly. 
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