Phase change material panel concept

As some of you know, I am in the process of rebuilding/improving an AliExpress battery pack. One of the design details I came up with was to separate the two banks of 18650 cells with lightweight extruded greenhouse polycarbonate. See the photo below.



Originally I was thinking of creating two plenums on either side of the battery and blow air through the open passages in the polycarbonate. But another thought I had was sealing one end of each polycarbonate panel with silicone seal, filling up each channel 90% with a phase change material like (liquid) paraffin, then sealing the open ends with silicone seal.

Curious as to your thoughts on the matter. Air-cooled? or PCM-cooled?

M

Looks a bit like the Energica battery cooling strategy:

However they have pouch cells backed against an aluminium cooling plate which in turn backs against this piece of extrusion. With plenty of Kapton in there for electrical insulation!

It will make it harder to keep weatherproof if you go down this route, but paraffin which melts at 50'C is a good move. It can absorb a lot of heat before fully melting. Of course, once molten you need a surface for it to shed that heat from, so an aluminium enclosure isn't too crazy an idea.

If the cooling purpose is repeated heat soaking, the PCM only gives a short period of buffering temp before its all melted and then it holds the cells at that melting point until they solidify.

If your purpose is a single race, it could be perfect.

Well air is easier to implement and if it is not adequate I could then add liquid cooling via copper tubing into the extruded openings in the polycarbonate.

M

liveforphysics said:

If the cooling purpose is repeated heat soaking, the PCM only gives a short period of buffering temp before its all melted and then it holds the cells at that melting point until they solidify.

Click to expand...

There are PCMs that slowly transform over a wide range at much higher temps (e.g. 50°C-200°C). Paraffin is less than ideal because of its lower range. But certain sugar/alcohol solutions would be perfect for bleeding heat away from a lithium pack. Not sure I want to be a mad scientist though...

see:

It's a nice concept but i think the polycarbonate will isolate enough to loose a lot of the value of it.

An alu plate or two with spacers would have a lot of thermal capacity as well as the possible function of guiding heat to a cooler area.