Busbars, terminal posts and board spacer

shadowsteve

Solar Enthusiast
Not sure if this is the right place to put this post or not.

I decided to make my own bus bars and terminal posts as anything that looked reasonable was shipping from outside of Canada when I looked on Amazon.

The posts use 1/4" bolts that press in from the back. They are printed using PLA and I did some red & some black. They are for my battery packs built with 280Ah cells. I also made a spacer to support the JBD BMS and hold it off the plywood it is mounted to.

The busbars are 1/4"x1" copper. I milled them from 1-1/2" stock that had rounded edges. They fit into the holders that are also printed with PLA. The countersunk screws hold the bars into the plastic. The small screws are for connecting light loads like Pi's, etc. The 5/16" bolts are pressed in from the back. I'm making another set and changing the spacing a bit as the small screws are too close to the edges and the nearest large bolt.
 

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shadowsteve

Solar Enthusiast
This is the drawing and STL for the busbar in the pictures above
 

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sprint2freedom

Solar Enthusiast
Looks great but I would not personally be comfortable with the choice of PLA. If a modest amount of heat is generated by a bad connection and/or being in a hot vehicle, those parts could start to warp or even liquify.

ABS seems like a better material for this application.
 

shadowsteve

Solar Enthusiast
Looks great but I would not personally be comfortable with the choice of PLA. If a modest amount of heat is generated by a bad connection and/or being in a hot vehicle, those parts could start to warp or even liquify.

ABS seems like a better material for this application.
I'm making another set of bars to space the bolts and small holes differently so I'll print in ABS when I redesign the fixture. It does have a much higher glass trans temp. The terminal posts are easy enough to swap out as well. Thanks
 

Short_Shot

Photon Sorcerer
Looks great but I would not personally be comfortable with the choice of PLA. If a modest amount of heat is generated by a bad connection and/or being in a hot vehicle, those parts could start to warp or even liquify.

ABS seems like a better material for this application.
ABS has a working temperature only somewhat higher than PLA, at roughly 176F/80C.

PLA is about 140F/60C maximum.

I wouldn't use ABS either if you're worried about heat. Neither is really suitable for the application.
 

shadowsteve

Solar Enthusiast
ABS has a working temperature only somewhat higher than PLA, at roughly 176F/80C.

PLA is about 140F/60C maximum.

I wouldn't use ABS either if you're worried about heat. Neither is really suitable for the application.
My info shows glass trans temp for PLA @ 65 & ABS @ 105. I'm not really concerned about heat issues. If things get hot enough to melt ABS or even PLA then it likely means the trailer is on fire.
 

Short_Shot

Photon Sorcerer
My info shows glass trans temp for PLA @ 65 & ABS @ 105. I'm not really concerned about heat issues. If things get hot enough to melt ABS or even PLA then it likely means the trailer is on fire.
For some background, I am a plastic injection molder and work with both on a daily basis.

Glass transition and working temperature are not always correlated either. Many materials will lose the vast majority of their strength before hitting tg, and the figure you want to look up is actually deflection temperature.

I've had PLA soften and warp in hot tap water and ABS soften in a hot car, again depending on the grade.
 

Short_Shot

Photon Sorcerer
Oh and HDT isn't even always the end-all either, because abs does this nifty thing where it will sinter at much lower than its hdt, which isn't really an issue unless it's touching itself but can be an issue if there's a mechanical load because its relatively soft ish at that point.

Hence the lower working temperature of most ABS relative to its HDT and Tg.


Now I'm not saying you can't use ABS here. I'm just providing info. If you're not worried about those temps then go nuts. I'm just saying if heat is a concern there are better options.


Like PETG.
 

shadowsteve

Solar Enthusiast
For some background, I am a plastic injection molder and work with both on a daily basis.

Glass transition and working temperature are not always correlated either. Many materials will lose the vast majority of their strength before hitting tg, and the figure you want to look up is actually deflection temperature.

I've had PLA soften and warp in hot tap water and ABS soften in a hot car, again depending on the grade.
Thanks for the great info. I'm no expert in plastics so it's great to have a response from someone who knows about it.

I was using this as my temp charts for the materials https://3dsolved.com/3d-filament-glass-transition-temperatures/

It shows PETG to have a lower glass trans but maybe that's not the key parameter. I'll do some tests on my initial prints that I have sitting here. I have some PETG and ABS to make test parts with as well
 

Short_Shot

Photon Sorcerer
Thanks for the great info. I'm no expert in plastics so it's great to have a response from someone who knows about it.

I was using this as my temp charts for the materials https://3dsolved.com/3d-filament-glass-transition-temperatures/

It shows PETG to have a lower glass trans but maybe that's not the key parameter. I'll do some tests on my initial prints that I have sitting here. I have some PETG and ABS to make test parts with as well
For some reference as to why glass transition is the wrong property to look at, look up the Tg of polypropylene once.

Most of the 3D printing community is... not great about correctly identifying properties and processing conditions of polymers
 

Short_Shot

Photon Sorcerer
Just don't forget this all largely depends on the grade you have.

Even two types of nylon 66 might have a difference in working temp of 40c.
 

Short_Shot

Photon Sorcerer
Oh and I almost forgot the whole thing gets funky with annealing, which I think was touched on in that link.

Petg has a really strange behavior where it will change from amorphous to semi-crystalline and in doing so it's thermal properties change dramatically.

When processing the stuff in it's amorphous state (like after it's been melted once already) you actually can't dry it because it's tg is so low it'll stick to itself and turn into a block in your dryer.

This goes for 3d printed objects too.

BUT! You can re-crystallize it to get that high temp state back. We use special equipment for that, but for a 3d print you just need an oven that can reach the right temp.

And you must account for a bit extra shrinkage.


As I said though, if you're not too worried about heat then ABS is fine. It is pretty unlikely you'll have an issue with the ABS in your application. It's also less effort than petg.
 

JohnTHQ

New Member
Salt baking is a great technique to anneal plastic parts. Buuut i feel its just better to use the right material for the application. I am about to whip up some holders myself for a project on my sla printer with some high temp phrozen TR250LV resin.
 
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