I designed a simple 3D-printed solderless battery pack.

Mazzz · Jan 19, 2019

Hello there, this is my first post but I've been interested in building battery packs from used batteries for quite a while. I wasn't happy with the current solutions of spotwelding where expensive machines are required, or soldering which damages cells.
Another major problem is that they are pretty permanent. When a cell dies then the whole battery back has to be dissasembled and reassembled, and it is pretty hard to isolate which battery is under preforming.

I've designed a simple 3-d printed enclosure that is made up of only plastic and nickel strips. Here are some pictures:

Basically two nickel strips are inserted into the bottom and the top of the enclosure and then screwed on with the plastic cap to keep them in contact with the battery, simple. At any point you can remove the nickel strip to access the cells and get them out!

Please suggest any improvement or any possible issues that you can see. If people want to use this design themselves I am happy to upload the 3D file.

spinningmagnets · Jan 20, 2019

That might work fine at the negative end, but the entire bottom and sides are charged with the Negative. This means vibration can cause anything that is rubbing against the shoulder on the positive end can wear through and cause a short.

You might add some additional protection to just barely cover the shoulder on the positive end. Then press a dimple onto the nickel ribbon that protrudes down into the center.

You might also consider drawing up a skeletonized version to let heat escape from the sides...I'd like the sides to be hex shaped (six sided).

Previous experiments showed that closed-cell "Poron" foam makes an excellent "spring". I'd like to suggest a round depression under the screw-in cap where a disc of Poron can be glued to act as a spring. Maybe have a second cap design that has a deep enough cylindrical depression, that the builder can insert a tiny coil-spring.

Adding some type of spring makes allowances for heat-expansion of the cell, while still maintaing pressure on the nickel ribbon that would stay reasonably constant in spite of minor cell expansion.

Mazzz · Jan 20, 2019

spinningmagnets said:
That might work fine at the negative end, but the entire bottom and sides are charged with the Negative. This means vibration can cause anything that is rubbing against the shoulder on the positive end can wear through and cause a short.

You might add some additional protection to just barely cover the shoulder on the positive end. Then press a dimple onto the nickel ribbon that protrudes down into the center.

You might also consider drawing up a skeletonized version to let heat escape from the sides...I'd like the sides to be hex shaped (six sided).

Previous experiments showed that closed-cell "Poron" foam makes an excellent "spring". I'd like to suggest a round depression under the screw-in cap where a disc of Poron can be glued to act as a spring. Maybe have a second cap design that has a deep enough cylindrical depression, that the builder can insert a tiny coil-spring.

Adding some type of spring makes allowances for heat-expansion of the cell, while still maintaing pressure on the nickel ribbon that would stay reasonably constant in spite of minor cell expansion.

I want to make this design as simple as possible so I will probably skip on the foam for now, although I might consider it if any cells get damaged or cells lose contact over time.

Hex shaped cells would definitely be cool, when you can put them together and they fit perfectly, but my ability to 3d print to any shape adds sturdiness and saves space in the construction. I will definitely be adding in your suggestion to let heat escape, I'm unsure of the best way to do this for now, maybe like you said a skeleton structure with loads of support or maybe just a few gaps in the construction.

Thanks for your suggestions, I appreciate it.

spinningmagnets · Jan 20, 2019

You're welcome. You are on the right track. There are similar designs floating around or already in production. Having several types to compare each aspect of their design is a good thing for all of us.

Smoke · Jan 20, 2019

A spot welder really isn't terribly expensive. It's cheaper than a 3D printer...

But I would suggest trying to align the print layers parallel to the long axis of the cell so you don't have weak seams in the middle of your tube.

I think spot welds, good spacers and a bit of glue is pretty decent but if you like the tubes, at least try to avoid adding a weak spot.

tahitiboob · Jan 21, 2019

hello

very good idea I want the file if it is possible until how much current can we go?

wil · Jan 24, 2019

Nice design, I like that is it so simple and doesn't need anything special other than just a nickel strip, vs the springs and things other designs need.

Couple of points though:
1. The screw fittings don't need the hex top if you are using a screwdriver to tighten them, you can shorten them by removing this (probably make it a female hex at the same time instead of Phillips)

2. In this design if one of the screw fittings gets loose then you will lose contact with a cell. In a pack with paralleled cells this could lead to one cell being out of balance vs it's paralleled cells. Now if contact is brought back you can have 2 cells at completely different voltages short out over one another... :bolt:

If you could implement a locking mechanism of some kind to secure the screw fitting down that would greatly reduce the risk of this occurring.

Also if you introduce cutouts as suggested above you actually will save material and be able to print them faster!

spinningmagnets · Jan 24, 2019

I like the "hex/Philips" cap (perhaps add a straight coin slot into the Philips), but...it should be very easy to provide several options for whatever various builders might want to print for themselves.

lionman · Jan 24, 2019

I like the idea. If the screw cap an handle a decent amount of torque then you should end up with a connection capable of quite a bit of current. I would be a little concerned that it could vibrate loose though.

Could you also have a second set of slots for the nickel strips at 90 degrees from the ones you already have to support additional series connections? At the moment the design is limited by the current carrying capacity of a single nickel strip, unless you add additional strips stacked on top of eachother I guess.

1N4001 · Mar 24, 2019

Very nice! I think this has some potential. A few comments tho.

- Why use Nickel strips? Nickel is used in welded packs because the low conductivity aids welding. Since you're not doing any of that, better use (tin/nickel-plated?) copper

- Add some slots to aid heat dissipation and reduce weight

-

lionman said:
Could you also have a second set of slots for the nickel strips at 90 degrees from the ones you already have to support additional series connections? At the moment the design is limited by the current carrying capacity of a single nickel strip, unless you add additional strips stacked on top of eachother I guess.

Good point being brought up here, but I'd actually consider 60°, so that a more compact hex/honeycomb-style layout could be done.

-

spinningmagnets said:
Previous experiments showed that closed-cell "Poron" foam makes an excellent "spring". I'd like to suggest a round depression under the screw-in cap where a disc of Poron can be glued to act as a spring. Maybe have a second cap design that has a deep enough cylindrical depression, that the builder can insert a tiny coil-spring.

Another very good point. Simple screw-cap solutions will not hold long. Not only will vibrations work them loose over time (use threadlocker!), they also offer little elasticity, which will lead to microscopic arcing. Some kind of elastic element is certainly needed.

SniperGaulois · Mar 25, 2019

That's a very cool design!!! seriously, it's a new approach. best i've seen. If I had seen this some time ago, I would have tried to optimize and study it. You'd just have to put a spring in there and a way to fasten the screws. a slot in a the lids for a carbon fiber bar would do it for 1 gram extra. You can arrange it to honeycombs too which is very cool. If you can mold silicone tubes, then they can act as the spring and it would reduce the weight, a silicone pouch version would only last about 5 years safely. It would be difficult to design, but I would fork your idea to a silicone version because I like silicone very much as a material. I just checked some ideas for silicone fastenings on images too.

I designed a simple 3D-printed solderless battery pack.

Mazzz

1 µW

spinningmagnets

Moderator

Mazzz

1 µW

spinningmagnets

Moderator

Smoke

100 W

tahitiboob

1 W

wil

10 W

spinningmagnets

Moderator

lionman

100 W

1N4001

100 W

SniperGaulois

10 kW

Similar threads