Flat temp sensor between cells?

[pshoe]

Has anyone used a flat temp sensor or a temp sensor between a cells? I'm exploring ways to get something like a core temp on cells be potentially placing a sensor between prismatic cells. This is to perhaps more precisely regulate temps with heating pads and to ensure the cells are at the correct temps for charging and discharging targets.

I have not yet decided on BMS' for testing the heat function nor do I know the specs on the sensors provided by say JK or JBD.

I'm having some silicone heat pads manufactured for testing. I've considered having a silicone divider of the same size manufactured with a sensor embedded to ensure somewhat of a consistent surface so I don't make a dent with the sensor. For that I'll need to decide on a BMS and I'm not there yet.

The battery is going in vehicles that can be in some very cold places. Trying to get as precise and possible with the analysis so I know how to fall back on what's most practical and reasonable that works well enough. I'm not sure taping a sensor to the surface of a cell inside the case gets me what I need, but I'll be testing.

Anyone have any experience or advice?

 

[wpns]

In another thread, someone mentioned that the positive(?) terminal was a pretty good indication of the temperature of the entire cell. Not sure how much that helps, but you would want to get the exterior and interior temperatures of the battery in order to make sure that no part of it was below your under temperature limit.

 

[pshoe]

Thanks. That's helpful. I have seen people say both negative and positive terminals.

I've found some 50mm thermistors that might work. I also located a 10 thermistor data logger that should help with sizing and calibrating the heaters.

 

[wpns]

I also located a 10 thermistor data logger

URL?

 

[pshoe]

10-channel NTC thermistor-based temperature logger - Share Project - PCBWay

This project is designed to be a 10-channel temperature logger based on 10k NTC thermistors.I designed the board with JST connectors, so it is easy to connect the thermistors to the board. It is easy ...

www.pcbway.com

 

[wpns]

10-channel NTC thermistor-based temperature logger - Share Project - PCBWay

This project is designed to be a 10-channel temperature logger based on 10k NTC thermistors.I designed the board with JST connectors, so it is easy to connect the thermistors to the board. It is easy ...

www.pcbway.com

Nice! Let us know how it is, I can't tell from the webpage if the assembly means you have to supply the parts? Either way, it'd be nice to know if the 10 sensors all read the same (or if there's a calibration process).

 

[pshoe]

Nice! Let us know how it is, I can't tell from the webpage if the assembly means you have to supply the parts? Either way, it'd be nice to know if the 10 sensors all read the same (or if there's a calibration process).

Sure. With PCBway you can get the board and parts and assemble yourself or have them assemble. The SMD parts on this board aren't tiny so I think assembly is possible by most that have a little experience. The code isn't that complex. If you use 10k NTC thermistors you can install the 10k resistors and set all 10 connections to use the 10k value for voltage divider. For lifepo4 uses I'd imagine the 10k/10k gives the most flat curve over the range we are interested in. So if you want PCBway to build it just leave the default BOM. If you had other needs this is pretty flexible. It's not all that polished, but it can do the job on a test bench.. or in my case a deep freeze or an industrial freezer that goes to 60 below. It doesn't make connecting the display elegant like you would want, but buying and not making something like this saves me time.

 

[wpns]

With PCBway you can get the board and parts and assemble yourself or have them assemble.

The thing I couldn't parse was if I bought the 'assembled' version, do they supply the parts or do you have to buy to the BOM and send them in?

I have an application for something like this, but the last thing I need is another unfinished project.

 

[pshoe]

For this project they supply the parts. You still have some work to connect things and load the code.

 

[pshoe]

You can also look at this one. He has a Tindie page for it. Very reasonable price for 60 inputs. Also easier to use if you are sourcing cheap thermistors with no connectors.

A2D 64CH Data Acquisition (DAQ) Board - A2D Electronics

A few years ago, I made a PCB to aid in measuring a bunch of thermistors for some thermal testing on battery modules. I’m finally getting around to creating some documentation for it so it can be helpful for others as well. I previously showed this board in the JLC PCB Assembly post. Store link […]

a2delectronics.ca

64 Channel Data Acquisition board for 10K NTC by A2DElectronics on Tindie

64ch data acquisition board with easy thermistor connection interface

www.tindie.com

 

[MattiFin]

Thermocouple wire is available down to 0.1mm thickness. Cheapo hack is to buy fine-stranded thermocouple wire and separate each wire strand from the bundle. 5 usd for 50x 1feet long thermocouples.

 

[pshoe]

That's interesting. Have you used that approach before? What did you use for the controller?

The unspoken feature I was also hoping to capture was replacing the BMS oem sensors with my sensors.

DIY ring terminal thermistor, flat thermistor, thermistor embededed in silicone heat mat, embedded in fr4 separator...