3d printer filament in battery pack

john2364

100 mW
Joined
Nov 22, 2010
Messages
36
I am going to be building a battery pack soon for an ebike. I was planning to do PETG since it has a glass transition of 80C. I was thinking that PLA might not be sufficient since the glass transition temp is around 60 for it.

Is it reasonable to assume that the battery pack will not get above 80c unless there is something seriously wrong with it?
 
PLA can be annealed to achieve 150C temperature before going soft. Have you tested your battery for peak temperature as having your battery stay at over 60C is detrimental for its longevity. Think about printing position, the case will be most its weakest in between the layers. Maybe 3d print a mold and make the case out of fiberglass?
 
about the strength, just make sure you have a compression mechanism perpendicular of the direction of the layers (threaded rods could be a good option)
 
I already made them out of PETG. I know that you can anneal most PLA but I had PETG around anyway. I orient my layer lines according to stress points. These cell holders should have very little stress though. My battery case though: that is a different story
 
Your battery pack shouldn't get more than a bit warm if properly specced. You won't be melting anything from your 3d printer unless your pack shorts.

Don't use PLA for a battery case, it's fragile. That can apply to PETG prints too if you don't pre dry the filament and it's been sitting open for too long (hygroscopic).
 
parabellum said:
john2364 said:
Is it reasonable to assume that the battery pack will not get above 80c unless there is something seriously wrong with it?
It is reasonable to design that your pack never gets over 60C.

what about the sun? depending on the color of the pack it could get very hot from direct sunlight. i have seen PLA melt in the back of a car on a sunny day.
 
nieles said:
what about the sun? depending on the color of the pack it could get very hot from direct sunlight. i have seen PLA melt in the back of a car on a sunny day.
PETG is reasonable choice, but I would try to get no direct sun impact on the cells and allow some convectional air circulation if possible.
PLA has many problems, not just heat, being biodegradable it can get unusable, over time, by many factors.
 
Thats crazy. I have been printing for 4 years and never knew that PETG was also biodegradable. I am considering adding some air vents my only concern is water in the battery pack. could be more exposed to moisture though.
 
Sorry, I was confused. I thought that someone was saying that PETG was biodegradable and I did not think that it was lol.
 
If you are allowing the pack to get above 60C (Which is very hot... burn you quick hot...) there will be other things to worry about.

so -

* Regular Use
* Failure mode

...

Failure mode is ... eh... an ugly subject. We are all still learning what to do when things go sideways. Just make sure that the low melt temp materials are not used for any insulating. Do your insulating with rigid, high temp, low-leakage materials. The case it all resides in - can be duct tape - IF - you are not depending on it for heat sinking


As for Regular use

Dont leave it in the back window of your car in summer in the desert
Dont drive the cells so far past their continuous C rating that you make that much heat
I have never, in my career, driven a lithium pack (as measured external) anywhere near 60C - and - had much more fun with the pack.

Know what I mean?

That said, there are a lot of products on the market which push cells to the absolute limit. They all end up needing heat sinking or active cooling. For a small ebike pack - I have always utilized air cooling and good sense - for good results.

Let us know what you find :p

-methods
 
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