Best filament for a battery enclosure?

So I’m considering getting a P1S AMS combo due to the A1 recall, and this has got me thinking about some fancier filaments that need an enclosure for printing functional parts which previously wouldn’t have been possible on the A1.

One of the projects I’m working on at the moment is a custom ebike lithium ion battery pack made out of several individual 21700 lithium ion cells, for which I have designed an enclosure and internals to be 3D printed.

The main requirements I can think of that the filament needs to fulfill for that kind of use case is:

  1. Must be impact resistant. If the bike gets into a crash I need to be 100% sure that the enclosure will not be punctured and crush the battery cells inside.
  2. Must be durable. If it gets scuffed up over the years just from rubbing against things occasionally this mustn’t meaningfully compromise the strength of the part.
  3. Must be able to survive outdoors for an infinite period of time. So this means a decently high deformation temperature to resist sitting in direct sunlight in the peak of summer for hours, as well as things like enough UV resistance to survive outside.
  4. Must not be electrically conductive. I’m not sure if carbon fibre filled filaments have this issue, but the filament cannot be electrically conductive as I will probably be using it for the internals as well which will be in direct contact with the battery cells including their terminals.
  5. Must be somewhat stiff, but I don’t think it has to be super stiff because it’s only holding the weight of the batteries and itself in a normal scenario (about 4kg). Mainly I’m saying this to rule out things like TPU which have incredible impact resistance/toughness, but which would deform too much under an impact or the static weight of the battery cells.

Originally when I had the A1 and other unenclosed printers, my options were mainly limited to things like PLA, PETG and TPU, of which PETG seemed like the obvious best choice as it is not too soft like TPU and is not brittle like PLA.

But now with the P1S, what would be the best choice that fulfills these requirements, or just generally what is the best for an outdoor battery box like I described?

I’ve looked at things like ASA, PC, PAHT-CF, etc. but have had a hard time picking the best one between them for this application.

P.S. I’m happy to buy a hardened 0.4mm nozzle and gears as well, in order to print carbon fibre filled filaments if necessary. I also currently have some dry boxes with desiccant for filament storage, and a filament dryer that goes up to 55C, so hygroscopic materials such as nylon probably shouldn’t be an issue.

ASA or PAHT will be good… nylon stronger and more flexible but more expensive.

Thanks, I looked at those and yeah it’s certainly quite the price difference. I suppose for my application, the extra strength, stiffness and heat resistance of PAHT-CF aren’t really needed compared to ASA for the price?

Also, another thing I thought was strange was that according to Bambu’s own filament guide (Choose the right filament - 3D Filaments Guide for Bambu Lab Printers), it shows PETG as having higher impact resistance than ABS and ASA, but I thought that generally it was supposed to be the other way around and that PETG is more brittle than ABS or ASA?

Similarly, PC is shown as having lower impact resistance than ABS and ASA, but I always though that PC was supposed to have incredibly high impact resistance, after all they make riot shields out of it for that reason?

PC i super hard but super brittle, like PLA but stronger. PETG is somewhat flexible so it can take a hit, kind of like Nylon.

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You can look around and you will typically see ABS/ASA as more impact resistant than PETG, so not sure why Bambu is saying otherwise. PC tends to be stronger in almost every way compared to other filaments, except for impact strength. How well it performs with impacts depends on the filament brands. I’ve looked and it appears to be kind of all over the board.

PA-CF filaments tend to be quite strong and are probably top of the list for impact resistance, but they are on the low end for deformation. After printing, it continues to absorb water and while that increases its impact resistance, it decreases its ability to resist deformation. Honestly I’d probably not use any Nylon filament that’s expected to weather the elements. Plus I wouldn’t trust that it isn’t conductive, though you could probably use a glass filled filament as an alternative.

For your use case, I’d probably go with ASA. It’s has great impact resistance, more durable than PETG (PETG scratches easy), temperature and UV resistant, and does not tend to deform like petg or nylon. ABS has all the same properties as ASA, but is not UV resistant, which is why I wouldn’t suggest it.

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Thank you both @maximit @RandomKhaos, I’ll probably go with ASA as you suggested.
Unfortunately, it’s currently out of stock on the Bambu UK store in black which is the colour I would prefer. Does 3rd party ASA work well with the P1S, and if so do you have any particular brand suggestions? I’ve used eSun PETG before but have no idea if their ASA is any good.

Also, in the slicer would you normally use the Generic ASA profile as a starting point for a 3rd party ASA, or adapt the Bambu ASA profile instead?

Ive used a lot of Eryone ASA and its great (and on sale for $18 a roll when you buy in bulk), so is Polymaker as its probably the OEM for bambu filament. You can start with generic profile, or bambu as they are very similar, the main difference is the flow rate.

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I’ve been using Polymaker Polylite ASA, which Bambu Studio has profiles for. It’s been working rather well with no real tweaking from the base profile. It’s the same price as Bambu’s ASA at $30 a roll.

While I was verifying prices on Polymakers website, I was reminded of their Polymaker PolyMax PC filament. It’s $39 a role and is one of their toughest filaments. It out performs their ABS and ASA in every metric. It’s impact resistance is extremely high compared to many other filaments. It’s not quite as UV resistant as ASA, but it will do well outside. Might be worth checking out.

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I imagine your box is going to be quite large, in which case you might find ASA and ABS are going to be difficult to print without warping. I’d consider just using PETG and make an impact absorbing outer casing in TPU, so you’ve got the best of both worlds.

ASA is the choice here for your project. Polymaker ASA is a god option. I’ve used it for car parts, high temp gears, enclosures, and anything else outdoors. You might avoid black so that your not attracting sun/heat as much.

PC is hard on printers and it also mars easily. ABS is not UV stable. TPU is a mess to print with if you need snaps or detailed mechanical structure. PAHT-CF is very tough but, 2x the cost of most other filaments for the same amount.

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Yes, in my case the final enclosure is going to be about 420 x 140 x 110mm so I plan to split it in half, print the pieces separately and then join them with a special glue such as E6000 glue, which sets relatively hard but still has a small amount of give to give it higher impact resistance.

So in that case the halves would be roughly 210 x 140mm XY on the bed, which is relatively large, but I thought that bambu’s enclosed printers like the P1S and X1C are supposed to be able to print ABS and ASA without warping problems due to their enclosure? It even says on the P1S product page that ABS/ASA is under the ideal filament list?

As a side note, I’m not sure exactly why the X1C is “ideal” for PA and PC, but the P1S is not? They both have similar hardware and are enclosed, so the only difference I can think of is that the X1C has a 120C bed instead of the 100C bed on the P1S?

Thanks for the suggestions, so far I agree it seems like ASA is the best option.

I did consider that a black enclosure might heat up a lot more during the summer in direct sunlight, but if it’s sitting outside for long periods of time, presumably it would still absorb a lot of IR heat even if it’s white, and would heat up from the surrounding air via convection?
Also, you could say that having it be black would help transmit heat more quickly from the inside to the outside of the enclosure when the cells are generating heat when in use (since the enclosure will be watertight)?

Other than that, I suppose my main reason for using black is an aesthetic choice, and I feel like white (or some other solid colours like red, green or blue) would stand out too much for a battery enclosure, when typically they are usually fairly muted colours like black or dark grey.

But if you think the heat absorption really will be an issue during summer, then I could consider some lighter colours like grey or white?

As far as a I know, grey or any other color won’t offer a significant improvement on heat reduction over black. So, if you’re wanting black for aesthetics then you might as well go with that. White would probably turn yellow-brown over time and even if it didn’t, it would scuff.

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When the batteries are put under load, or maybe charged as well, won’t they potentially get hot? Maybe even possibly very hot?

If so, then you’ll need to pick a material that can comfortably handle the worst case high temperature scenarios and still maintain an appropriate safety factor.

What you want is Polycarbonate. And not the polycarbonate for posers where they blend it. Pure PC. 3DXtech make some good PC.

Let’s be honest you’re not really going to be using that many fancy materials. P1S is still limited it opens the door to some new things and to start tasting the engineering grade stuff.

Pick up some Vision miner nano polymer too. Every else is trash and that’s going to be your engineering grade prep.

Also PC smells. Some smells really really bad. The stock filter won’t do anything. Pick up and activated carbon filter to throw in that room. Then close room and turn that on your printing. You pick up something for about $80. The Levoit 300 works pretty good… after you go on cults and buy the STL for activated carbon basket for the filter. Stock filters have some in but it’s not enough for a few bucks you can get one that holds more and is refillable just drop it into the center. I got one of those my print room in my house and that takes care of everything almost on printing stuff like Teflon and delrin That gets piped directly outside that’s some nasty stuff.

Yes, the battery cells can get hot during charging, discharging, or just from the ambient temperature during summer. I of course have a BMS to use with the cells which cuts the input/output to the pack automatically if the internal pack temperature is too high or low. The cells I’m using are rated for up to 60C when charging or discharging, so during use I can expect them to get up to a little less than that before the BMS cuts power to let them cool off.

It’s hard to find solid numbers from looking online, but 60C/140F seems like the upper limit on how hot a generic enclosure can get from sitting outside in the sun during summer. Looking at the materials we’re talking about (ASA, PC, etc), they all have heat deflection temperatures of 100C or higher according to Bambu’s own filament table. Even PETG could withstand 69C before any deflection, so I’m more worried about the cells getting too hot at that point than the enclosure softening and falling apart.

When you say pure PC, I’m assuming you’re implying that Bambu’s PC is not pure and is a blend in order to allow it to be printed on bambu printers? Also, if it is true that it is a blend, then wouldn’t that imply that pure PC would be difficult to print on even an X1C? It seems like the P1S can just about do Bambu’s own PC (maybe with some difficulty due to the 100C bed temp limit), so I’m not sure if more difficult/pure grades would even be printable?

And yes, I know I am not going to be printing super fancy materials on the P1S, what I meant when I said fancier was simply things that can be printed in a passively heated enclosure like the P1S and X1C have. So for example, I would expect almost all the filaments on Bambu’s website can be printed on the P1S given that they state that in the specs, with the exception of maybe PC and PA which might have a little trouble but aren’t entirely excluded. As far as I can tell, the only reason I could see that the P1S would have trouble printing them when the X1C wouldn’t is the 100C vs 120C bed temperature difference between the two.

Regarding the Vision miner nano polymer, thank you for the suggestion, but I was under the impression that the whole point of textured PEI beds (such as is provided with the P1S) is that they can be used without adhesives, since the texture gives them a naturally weaker adhesion when cool than say a smooth PEI bed, so they don’t need any glue stick or other release agents?

Lastly, regarding the filter, I’m a little confused because you mentioned getting an activated carbon filter, but isn’t that exactly what the stock filter is in the X1C and P1S? It may be my naivety (as I don’t have any experience using the P1S/X1C), but it would seem a rather flawed design decision if they put in a filter that did a poor job at filtering the fumes from printing Bambu filaments that Bambu says these machines are compatible with?

If it really is an issue though, I do have an air purifier with a 3 stage filter including a HEPA 13 and an activated carbon filter, which I can use if the stock filter ends up underperforming.

I print 90% of my models in ABS/ASA and have a roll of polymax PC for those special projects.
I have printed hundreds of models all in a p1p with a enclosure that i build myself without any problems.
With the pei sheet it should print most of the time without any adhesive added, if i have problems i just put some hairspray and that’s it.

One important thing when printing with ABS/ASA is to use a brim, that really helps to stabilize the model and avoid lot’s of problems.

Don’t be afraid to try filaments from other brands, my p1p has eaten every brand i throw at it.
Polymaker, Prusa, Sunlu and Esun work really good.

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Fair enough. I was trying to think about it from the perspective of, say, an Underwriters Laboratory evaluator, who would probably ask questions like “And what happens if the temperature sensor in your BMS fails? What then? Would that failure possibly lead to some other, catastrophic failure? Or could the system survive even that without risking injury or loss of life?”

However, I’m only guessing how such a person might think about the problem or what kind of questions they might ask. or what kind of answers they may or may not deem acceptable. And where does one draw the line in such matters? It seems that these days we are living in a world where, for example, UPS won’t knowingly transport even a single CR2032 lithium coincell battery without UPS designating it a hazardous shipment and charging a higher fee to cover extra handling. For real.

Thanks, it’s good to hear that the P1S (or in your case the P1P + enclosure) can handle ASA and PC without problems. Would you suggest ASA or PC would be better for this kind of application?

Also, I will have a look at some 3rd party brands, especially if bambu doesn’t restock their ASA or PC in black soon, I just preferred to go with bambu filament to start with since their extrusion multiplier and pressure advance values are already pre-tuned so I shouldn’t have to mess with them to get good prints out of the box. Also, the RFID tag is nice for saving time inputting the type and colour of each filament manually into the AMS settings so that you don’t have to manually pick the correct AMS slot to print from when you’re hitting print in the slicer.

But again, those are just nice to haves, and if Bambu’s stuff is out of stock then I guess I will just have to suck it up and go through EM and pressure advance tuning.