Pack cooling

A

Allan Gilbert

New member
Joined
May 10, 2017
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11
Hi all, I don’t post much but have a question about cooling of packs.
I know a lot of you have gone the air cool route but was thinking on using a copper pipe through a pack and doubling it as the main earth bar.

Also have though a lot about using the phase change effect of wax’s for cooling as it takes a fair amount of heat to change it to liquid and would also make for a quick indicator for heater cells. Wax’s can be gotten at various melting temps so anything that hits say 70c to 80c the wax melts away from the cell leaving it exposed to easy view.
Have already used a similar experiment for a intercooler for a car but the constant spikes kept the wax liquid all the time so didn’t quite work.

Yes i have considered the fire aspect and there are other substances out there that will do the same effect and may actually act as fire deterrents.

Anyway thoughts ect from you guys
 
If your battery is getting and it's not due to the outside temp, you should consider changing the design. A well designed battery won't heat (much)
 
Cooling is something I have been working on for a high powered scooter (2kw+) , but thought it would make a great indicator for heater cells in wall packs. Heater melts the wax and it leaves it standing by itself, so easy indicator.
 
If a battery in a powerwall raises justs 5 degrees you have issues with your design. Cooling away or forcing that will make sure you cant see the heaters you got. Cooling as such is waste of time
Cant compare EV with powerwall. On EV of those types you have 10 or even 50x the current going through.

There is 2 rather simple way of geting notification if you have a cell or 2 that heats up the pack. Air-cooling with high temp probe forded slowly through a sealed container. This with probe in each end can sense it.
Or IR pointing towards the packs in all directions :)
 
To put some numbers to this. My powerwall operates between 150ma - 300ma / cell thru the daily cycle. At this level, the cells have no noticeable temperature at all above ambient. As said above - I can attest that cooling is not needed at this level for healthy packs.
 
Allan Gilbert said:
Wax’s can be gotten at various melting temps so anything that hits say 70c to 80c the wax melts away from the cell leaving it exposed to easy view.
Click to expand...
Very interesting, but it would require a visual inspection. Not realistic with thousands of cells and a powerwall that should ideally be monitored 24/7.
Maybe if the wax could be turned into a long sensor wire looping around every cells, that then breaks/melts and activates the safety shutoff or an alarm if any one cell goes above 70C?
 
Yeah thought maybe black wax with a light sensor on the other side or something. My setup has the batteries vertical on a draw but raised a little and sensor in a sealed box. Easy to make a warning buzzer etc.
 
Probably the best way to deal with cooling is to make sure your cells are not getting close to their max. continuous discharge current value with the load(s) you're applying.
 
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