Wooden Storage Case for 24V DIY

[OffGridForGood]

My Overkill BMS has two temp probes. They are pretty small in diameter. The official Overkill recommendation is to tape them to the side of a cell with Kapton tape. Does the Kapton tape exclude ambient temperature somehow? Does it work to place them between cells (which would give a more accurate reading of the actual temp inside of the battery)? I'm thinking with compression this could be something that would damage the protection around the cells as they expand, no? If so, could they be integrated with some sort of separation material to prevent that?

I tape one sensor on top of a cell in mid pack, and one on an opposite side of a cell, and call it good. All my cells are in double rows in complete boxes - enclosed to keep out dust, insects, rodents, fingers...
You need to add separation between every cell. The forum has a number of suggested materials for this.
The shrink wrap the cells come with is very thin, and the Aluminum case beneath is electrically continuous with one of the battery terminals, POS IIRC.
Generally you will want to top balance to get the cells close enough to the same potential near the fully charged state, that the BMS can just maintain this balance. If you're in a hurry, charge them up and get the pack working - in your set up you have access to all the cell terminals so you can 'bleed' a cell to lower voltage with an automotive bulb easily enough at any time. If you have a bench source you can charge a low cell (you don't need to disconnect the cells from each other to do this) to bring it's voltage up if needed on a cell or a few. If you have the app showing you all the cells's individual voltages, it is an easy matter to pull some low ones up, and pull some high ones down while monitoring all cells on the BMS app. Takes some time.

 

[740GLE]

My Overkill BMS has two temp probes. They are pretty small in diameter. The official Overkill recommendation is to tape them to the side of a cell with Kapton tape. Does the Kapton tape exclude ambient temperature somehow? Does it work to place them between cells (which would give a more accurate reading of the actual temp inside of the battery)? I'm thinking with compression this could be something that would damage the protection around the cells as they expand, no? If so, could they be integrated with some sort of separation material to prevent that?

My 8s is in a block shape, I was able to sneak the JK sensors down in between 4 cell corners, didn’t take any force at all.

I figured if ambient temps rise, the cell internal temp would be cold soaked and it’d take some time for them to rise up.

But then again I’m only worried about October before the battery is brought back south to live the winter in the basement.

 

[curiouscarbon]

My Overkill BMS has two temp probes. They are pretty small in diameter. The official Overkill recommendation is to tape them to the side of a cell with Kapton tape. Does the Kapton tape exclude ambient temperature somehow? Does it work to place them between cells (which would give a more accurate reading of the actual temp inside of the battery)? I'm thinking with compression this could be something that would damage the protection around the cells as they expand, no? If so, could they be integrated with some sort of separation material to prevent that?

the temp probes with overkill/JBD BMS are relatively hard, and i advise against any compression that would push them into the cell casing. that would damage the cells and increase likelihood of failure.

kapton or polyimide tape is good at electrical and thermal insulation, so it will provide some degree of "rejecting ambient temperature influence" so that the cell material is what will be mainly measured. try to ensure the wire is positioned so that the tape is not being pulled away over time. just gentle contact with the outside of the cell should suffice for most situations.

with two sensors, one near the center and one near a "far side" seems common and fine.

the cell terminals themselves are often the most leading indicator of overall cell temperature, but the busbar and interconnect also make that difficult both electrically and physically.

when in doubt, post a photo or drawing of a proposed thermometer placement and surely a few folks will share feedback.