SmartShunt + Temp Sensor = Any Cell in Bank?

[myersfamilyhome]

So my 16 LifePO4 cells are stacked on there side in 2 vertical columns because of space requirements. My question is, since the coldest cell in my bank is closest to the floor, can I connect the victron SmartShunt Temp Sensor to the lowest positive cell terminal in the stack (cell 8 so that I get the coldest reading from the bank or do I need to connect it to the end of the series of cells? I can't tell via the data sheet what the voltage requirement is for temp/shunt operation off this lead is.

 

[sunshine_eggo]

The temp sensor is also the voltage sensor. It must be on the battery (+) terminal.

 

[myersfamilyhome]

The temp sensor is also the voltage sensor. It must be on the battery (+) terminal.

Correct, but what is the minimum voltage to operate the shunt as well as a temp sensor? I would assume victron would have considered battery banks and placement of sensor when designing the product. You can't expect the placement of the positive terminal at the end of the series of cells to be the exact place where you need to measure the temperature of the whole bank.

 

[sunshine_eggo]

Correct, but what is the minimum voltage to operate the shunt as well as a temp sensor? I would assume victron would have considered battery banks and placement of sensor when designing the product. You can't expect the placement of the positive terminal at the end of the series of cells to be the exact place where you need to measure the temperature of the whole bank.

One of the most important features of a shunt is accurately measuring open circuit battery voltage. You are proposing to not use it to measure voltage.

Why would Victron have considered that when this system was originally designed for lead-acid?

Why would Victron assume someone would want the coldest part of their pack when the hottest makes more sense for temperature compensation on lead-acid system - of which there are dramatically more in service than there are LFP and certainly were when the BMV was designed?

You've bought something to use it in a way it wasn't intended. Don't assume a design flaw when you're trying to force a piece of equipment to do something it's not designed to do. it's not designed to be placed on the coldest portion of a battery. it's designed to provide a temperature value that's reasonable to apply to the entire battery for the purposes of temperature compensation during the charging of lead acid.

I have 7 temperature sensors on my custom NMC battery. 3 from the BMS, 1 from each Quattro (2), one from a BMV-702 and an SBS (which is only usable as a reference). What I have found is that my battery temperature varies wildly in different locations with different sensors, and it's up to me to determine through trial and error how to manage it. What I found is that the since the BMS does the managing, I had to experimentally determine how to manage the pack based on those temperature readings using the other sensors as reference and additional cell checks with an IR gun. As such, I set my low temp charging protection sufficiently high to ensure that the no portion of the battery is below 5°C when charging is enabled.

No one at Victron knew how you were going to build your battery.

 

[myersfamilyhome]

Well put. Thank you for grounding me. I was thinking to far outside the box, before you know it your head gets convoluted with noise, numbers, and silly questions.

 

[sunshine_eggo]

You just have noise, numbers and silly questions? I just want the screaming to stop.

 

[timselectric]

Thanks, I thought that I was the only one hearing that.