Temp sensor for BMV-712 or not?

rhyno

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?

Horigan

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.

rhyno

Thanks for the tip @Horigan. We will be installing the shunt in the battery box. 

crampshaw

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. 

rhyno

@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.

Denny16

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

crampshaw

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.