I’ve spent the last few months designing a super solid battery pack. It uses a 3d printed frame that secures the cells, nickel, and balance leads into place. I’ve gone through about 2 dozen revisions and a couple hundred bucks worth of filiment, but I finally finished the first prototype. I’m calling it the Loud Pack.
I orginally had the nickel fitment really tight so that they snapped in, but it ended up requiring too much post processing when I switch to pa-cf (carbon fiber nylon).
Here you can see the extra long grub screws. 4 on top and 4 on the bottom which keep both sides locked together. I also have an extra piece of .4mm abs insulation in addition to the fish paper. After the grub screws, I install the bottom cross bars. It’s hard to explain this part as I didn’t take pictures, but I’ll explain this in a video at the end.
Towards the end of the video I explain the dilema I’m in. I’m worried about the criticism around not using fishpaper to insulate the p-groups. I’d love to know what everyone thinks about this. Particularly @ShutterShock@Battery_Mooch@BenjaminF@TheBoardGarage@Skyart@Simeon@JoeyZ5 (using your nickel )
I’m guessing there no way there’s space for an air gap in the cell spacing?
Having the cells butted up to each other like that is not usually considered best practice.
Aesthetically though the pack is killer.
Without the data we need to say how well Kapton tape, fishpaper, and other materials can resist abrasion and pressure (from adjacent p-groups rubbing or bumping a huge number of times) we’re forced to fall back on what we feel is the most conservative recommendation, our “best practice”. Typically that is fishpaper.
IMO something must be used though. The plastic used for cell wraps is not enough to prevent adjacent p-groups from possibly touching over the life of the pack. They must stay apart even at (possibly) extremely high temperatures in addition to resisting pressure and abrasion.
Water resistance is a possible concern but opens another debate for fishpaper vs plastic (Kapton or other).
The use of high-temp plastic or fishpaper top insulating rings is absolutely mandatory though. Since no one makes thick Kapton rings we use fishpaper.
It’s important to realize that all of this really isn’t needed for a new pack. This extra insulation and things like a BMS are what’s needed to help ensure that the pack doesn’t eventually become a real safety hazard. These best practices for pack assembly can significantly extend the life of the pack and reduce the risk of using it as it ages.
I think this is what creates so much of the debate…some are only thinking short-term and others are thinking a couple years, or further, down the road.
Another issue…who is the pack for?
If for personal use then Kapton tape or even nothing between p-groups might be an acceptable risk for the builder. If the pack is being built for someone else then we must, MUST, do all we can to sure their safety. Even when they abuse the pack.
I totally agree. I have never made a pack without incorporating all the mentioned safety precautions. This pack is for myself. It was just an experiment to see if I could increase the packs overall structrural rigidity while not needing to use tape. The ultimate goal was to see if I could make it stronger, safer, and minimize the build time. And of course make it look nice.
I have definitely acheived the goal of increasing the strength without tape, and made it look nice, but I can’t claim that it is safer due to the lack of fish paper between the p-groups.
I plan on putting this pack through some serious torture for science, but I am going to redesign the model to use fish paper.
Thank you for taking the time. I appreciate the feedback.
It depends on the enclosure. This box has no extra space, but it’s 3d printed so I could modify it for an extra 1-2mm. I’m gonna give it a shot and try with fish paper.
I just built an 18s2p p42a pack for my vexr. I have it in a torquebox,
i used fishpaper on the cells, glued them with silicone, kapton tape,
all the insulation!
It still fit great, actually easier than the 15s3p 18650.
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