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Inspiration to build Solderless battery

Posted: May 27 2019 12:35pm
by laerciohj
Hello guys.

I'm from Brazil, I'm talking using the automatic translator, sorry for any mistakes.

I have seen some projects released that dispense solder. I imagined and tested various techniques until I got to the last prototype.

I used brass screw, I applied 5A current for more than 5 min and the temperature was below 30ºC. I believe that I support a lot more, but I did not have something more powerful to test at the time (I used an alogeno heater as controlling resistor with a dimmer). Using the original, spring-loaded connectors with only 2A the temperature was above 65 ° C.

By using the inner nut I can lock the cell turning the screw, gets very firm! Using a small piece of aluminum foil I increase the contact surface of the screw with the pole of the cell.

I hope it will inspire similar projects and enhancements.

Re: Inspiration to build Solderless battery

Posted: May 27 2019 1:40pm
by john61ct

Could only glue a 2-row of those holders right?

Added cost per cell, for say 70?

Re: Inspiration to build Solderless battery

Posted: May 27 2019 1:51pm
by billvon
laerciohj wrote:
May 27 2019 12:35pm
I used brass screw, I applied 5A current for more than 5 min and the temperature was below 30ºC. I believe that I support a lot more, but I did not have something more powerful to test at the time (I used an alogeno heater as controlling resistor with a dimmer). Using the original, spring-loaded connectors with only 2A the temperature was above 65 ° C.

By using the inner nut I can lock the cell turning the screw, gets very firm! Using a small piece of aluminum foil I increase the contact surface of the screw with the pole of the cell.
Looks like there's not much compliance to allow for cell swelling and shrinking with temperature. That's why people use springs.

Re: Inspiration to build Solderless battery

Posted: May 27 2019 2:35pm
by pullin-gs
Use large pouch cells w/clamps....this is only reliable high-amp solderless/weldless battery configuration for high-amps in my opinion.
This is a 10S1P 8ah pack I built for a 500w project.
Cells cost $50.
Stainless fittings and aluminum bar cost $15.
BMS $10.
Shrink $7
Range is 15 miles full-throttle 20-22MPH...30 miles when slow less than 10 MPH.
Bike/battery has 350 miles on it trouble-free.
clamps.gif
cells.gif
cells.gif (233.44 KiB) Viewed 1646 times
Range is 15 miles full-throttle 20-22MPH...30 miles when slow less than 10 MPH.

Re: Inspiration to build Solderless battery

Posted: May 27 2019 8:18pm
by Dak77
Pullin-GS : Do you have any pics of your complete pack? Is that $50 per cell or total? Do these have to be compressed to avoid swelling?

Re: Inspiration to build Solderless battery

Posted: May 27 2019 9:22pm
by Chalo
billvon wrote:
May 27 2019 1:51pm
Looks like there's not much compliance to allow for cell swelling and shrinking with temperature. That's why people use springs.
In this case, it's clear that the cell holder is positioned, intentionally or unintentionally, to function as a spring. That might not be reliable in the long term, but the spring rate is probably in a usable range.

The face of a brass nut seems like a pretty good electrical contact for the battery. Whether it has equally good contact with the screw pushing on it is less certain. If there are multiple turns of dry thread engaged, it's probably good in that regard too.

If I were going to use a brass screw as a battery contact, I'd want a short, stiff spring pushing the screw or nut into the cell.

Re: Inspiration to build Solderless battery

Posted: May 27 2019 9:25pm
by billvon
Chalo wrote:
May 27 2019 9:22pm
If I were going to use a brass screw as a battery contact, I'd want a short, stiff spring pushing the screw or nut into the cell.
Agreed, and that's what is missing here.

Re: Inspiration to build Solderless battery

Posted: May 27 2019 9:47pm
by john61ct
Isn't it the OP's intention for the compression tension to be from torquing on the thread?

That would certainly be lots more force than any spring.

But it is unclear if there is a brass thread (nut) firmly epoxied or something in the holder end wall.

Is it the case that the dimensional changes in use are along the length axis?

Re: Inspiration to build Solderless battery

Posted: May 27 2019 11:51pm
by pullin-gs
Dak77 wrote:
May 27 2019 8:18pm
Pullin-GS : Do you have any pics of your complete pack? Is that $50 per cell or total? Do these have to be compressed to avoid swelling?
This guy sold me my cells.......I built two packs....one 10S pack 36V pack for my trike, the other is a 3S3P 12v pack for my e-Kayak.
https://www.ebay.com/itm/20-SPIM08HP-3- ... 4442!US!-1
Pack is not compressed....only draw 20 amps sustained from it.
Here is the completed pack:
battery.jpg
battery.jpg (120.07 KiB) Viewed 1600 times

Re: Inspiration to build Solderless battery

Posted: May 28 2019 1:22am
by Dak77
Awesome. Thank you

Re: Inspiration to build Solderless battery

Posted: May 28 2019 1:32pm
by laerciohj
In this technique I believe the springs are expendable. By turning the screws I get a very tight grip against the poles of the cell and can not lose the connection. This support model I am using has four arms that tightly hold the cell and reinforce cell attachment.

The use of springs is also feasible, but these supports use steel springs, a poor electrical conductor. In my tests I managed to get around this involving the spring with aluminum foil, which is quite malleable and great electric conductor. In my test, 1 cm2 (1cm X 1cm) was able to conduct 5A without any relevant heating. Below 30 ° C for several minutes. I used thermal camera to check.

This is a technique suitable only for 18650 cells.

It may seem a bit more expensive, but this technique allows for easy maintenance and the brackets can be reused indefinitely by simply taking out the bad cell and putting the new one. Type 4 cell support may be used, which expedites the assembly. The holes in the bracket allow several ways of fixing.

The connection between the cells can be simpler than soldering point. Simply wrap each screw with a long copper wire. This design can completely eliminate welding.

I used Google translator to interact with you, sorry for the inaccuracy.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 2:22pm
by fechter
You might check out similar off-the-shelf versions. You can get some ideas.

https://endless-sphere.com/forums/viewtopic.php?t=87434

https://endless-sphere.com/forums/viewtopic.php?t=88051

Pretty much anything like these will be fine when they are new. The problem happens after a long time in use were either the metal surfaces get oxidized or the contacts lose tension. If it lasts longer than the cell, then things are good. As mentioned above, the cells expand and contract with temperature so the contacts need to allow for this. The plastic housing acts like a spring, but over a long time can flow and lose tension or crack.

You also need a high pressure on the contact point to prevent oxidation but too much force will dent the end of the cell. A pointy contact will have more pressure with less force but also less cross sectional area needed for high current.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 2:44pm
by john61ct
My thinking is conductive adhesive holding fine-stranded tinned boat wire fanned across the end face.

Rubber dome / dot between that and the case which is exerting clamping force.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 9:41pm
by laerciohj
Fechter, the cell expanding is new to me. This information is very relevant! What is the maximum expansion of a cell?

In my prototype it is possible to compress the poles as much as the size of the screw used. It is not the nut that will make contact with the pole, but the tip of the screw. Aluminum is poorly oxidable, it will withstand a lot. By being malleable, the aluminum foil can be kneaded and generate a broad point of contact between the tip of the screw and the pole of the cell. Aluminum foil will help insulate the air screw, preventing premature oxidation. This plastic holder is flexible, it has a certain spring capacity that will certainly fit the expansion of the cell if it is a few millimeters.

I used the vruzend kit and I do not recommend it. The connector of each module has poor spring function, often I lost connection in some cells. I suggested to them that they put copper alloy springs in place, but they ignored it. The vruzend kit is not trusted to maintain connection to cells. I made modifications to the modules: I added springs, copper wire and connector with ball of aluminum foil wrapped in the tip of the copper wire. In my test supported more than 5A for several minutes without any relevant heating, below 30ºC.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 9:47pm
by laerciohj
john61ct wrote:
May 28 2019 2:44pm
My thinking is conductive adhesive holding
If there is heating, the adhesive may not resist and take off, losing the connection with the cell. I thought about creating a glue with copper dust. This would also be a solderless construction.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 10:42pm
by john61ct
I mean off the shelf conductive adhesives formulated by the likes of 3M.

Silver loaded epoxy I believe.

There are also adhesive tapes, and also heatsink pastes, if adhesion is not critical.

My use cases are not high C-rate, do not anticipate high heat being an issue.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 10:49pm
by liveforphysics
The aluminum in that stack up will be fine when dry, but when moisture condenses in that gap between the surfaces, it will make a kind of 1 time use battery that has about ~0.6Vdc from the galvanic surface potentials. It will consume the interfaces through electrolysis corrosion over a period of weeks if exposed to humidity.

Using a copper-nickel interface, and protecting the surfaces from humidity with a good dielectric compound may last longer with ~0.3Vdc galvanic potential. Nickel plated copper, or copper-nickel alloy to the nickel can surface would be landing inside 0.1Vdc galvanic potential, which should last a long time with a good dielectric compound coating the surfaces.

The can's are so thin and delicate, I think you want to have something supple and conforming to interface with the can, or something smooth and flat with all radius'd edges. You also don't want more contact area than you have pressure to support pushing solidly against the can. If you get those parts down, then you need to watch everything's creep behavior in your sprung contact assembly to ensure the pressure won't relax over lots of temp cycles and time.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 10:55pm
by amberwolf
you should look up the resistance of those glues, it's way too high for that. there are various threads discussing conductive glues adhesives etc that explain the problems

Re: Inspiration to build Solderless battery

Posted: May 28 2019 11:30pm
by john61ct
My intention is that the fanned fine strands of tinned copper are in firm direct contact with the cell ends.

The rubber cushions / spreads the clamping force exerted by the case, holding that contact pressure firm under shock/vibration.

The adhesive surrounding the strands, whether a layer on conductive tape or as epoxy is simply to hold the strands in place, preventing lateral movement from any shock/vibration.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 11:32pm
by john61ct
Perhaps the tape is better, less adhesive so no chance of any getting between the wire strands and the battery ends.

Re: Inspiration to build Solderless battery

Posted: May 28 2019 11:34pm
by laerciohj
liveforphysics wrote:
May 28 2019 10:49pm
The aluminum in that stack up will be fine when dry, but when moisture condenses in that gap between the surfaces, it will make a kind of 1 time use battery that has about ~0.6Vdc from the galvanic surface potentials. It will consume the interfaces through electrolysis corrosion over a period of weeks if exposed to humidity.
I am surprised at this possibility. I intended to put the battery in a sealed carton without air contact, but I fear that lack of ventilation could contribute to overheating. Do you think I can get around this problem by creating copper foil connectors? Or brass? I do not notice oxidation on the aluminum foil that is used in cooking. Kitchens are sometimes damp places, with steam from the food water. I'll put a portion of the aluminum foil in water for a few days and measure the amper capacity.

Re: Inspiration to build Solderless battery

Posted: May 29 2019 1:01am
by liveforphysics
laerciohj wrote:
May 28 2019 11:34pm
liveforphysics wrote:
May 28 2019 10:49pm
The aluminum in that stack up will be fine when dry, but when moisture condenses in that gap between the surfaces, it will make a kind of 1 time use battery that has about ~0.6Vdc from the galvanic surface potentials. It will consume the interfaces through electrolysis corrosion over a period of weeks if exposed to humidity.
I am surprised at this possibility. I intended to put the battery in a sealed carton without air contact, but I fear that lack of ventilation could contribute to overheating. Do you think I can get around this problem by creating copper foil connectors? Or brass? I do not notice oxidation on the aluminum foil that is used in cooking. Kitchens are sometimes damp places, with steam from the food water. I'll put a portion of the aluminum foil in water for a few days and measure the amper capacity.

It's not the aluminum alone or the nickel cell alone that cause a problem in humidity, but the stackup of the two in contact with an electrolyte (like condensed water vapor) and becomes a single-use battery that corrodes as it discharges. If you protect from humidity (or other electrolyte) ingress you can prevent it from occurring. It's harder to keep humidity out of something than keep air out of something, because water vapor is a smaller lighter molecule than our own air (N2 and O2 dominate), but you can displace places an electrolyte could condense with something that's not an electrolyte like a dielectric compound (some greases etc).

Re: Inspiration to build Solderless battery

Posted: May 29 2019 7:06am
by laerciohj
I fully understood now. The idea of ​​grease is good, it really is a good insulation for moisture. In combustion car battery there are users of grease at the battery poles to avoid this. I think the problem with this is that high discharge lithium batteries tend to get hot, this could melt the grease and remove it from the pole.

There may be a minimum amount of air humidity to activate this effect. Perhaps constant ventilation, with inlet and outlet air vents, can ventilate enough not to allow the moisture to settle on these metals in contact, as well as assist in cooling the battery itself. But I predict that on rainy days there will certainly be too much moisture to come into contact with the battery, so I also think of complete insulation with a battery case. Maybe the grease and fan combination is good. It is always good to share ideas to be perfected.

Re: Inspiration to build Solderless battery

Posted: May 29 2019 8:06am
by fechter
laerciohj wrote:
May 28 2019 9:41pm
Fechter, the cell expanding is new to me. This information is very relevant! What is the maximum expansion of a cell?
It's not very much but I don't know exactly. It depends on the temperature range. I would guess less than 1mm.
If the cell is held tightly by the holder and it expands, it could deform something so it loses tension. There has to be a "spring" somewhere but it does not need much travel.

You also need to consider impact forces and vibration. A pack bouncing around on a bike going over pot holes in the road could see some significant forces due to inertia. The "spring" has to maintain tension during and after an impact.

All of the solderless systems I've seen will work fine in the short term but long term the oxidation of the surfaces or loss of contact force seem to cause problems long term.

Dielectric grease may be a way to slow down the corrosion issues.

The conductive epoxy might be viable if you have a very thin layer with a lot of surface area so the length of the epoxy conductor is very short and fat. Epoxy will at least keep humidity out and not need any additional clamping force once hardened. This would certainly be worth testing by measuring the voltage drop across the connection at the maximum cell current. I imagine putting a small blob of epoxy on the end of the cell and then clamping a metal strip against it until it hardens. The strip could be peeled off if the pack needs service.

Re: Inspiration to build Solderless battery

Posted: May 29 2019 8:45am
by john61ct
To explain my use of tinned copper boat wire.

Each cell to have more-robust-gauge-than but similar-style-to balance wires extended out to the sub-pack case,

using mounted jacks capable of supporting the max C-rate amps for charge or discharge,

Deutsch DT/DTM if waterproofing desired.

No other connection to / between the cells.

A buss arrangement for the desired xPyS pack layout, just unplug that to return to each cell isolated.

Allows monitoring groups in use, cells when not, balance charging, per-cell load testing etc without physical disassembly.

Yes higher overhead cost, stronger incentive to go to larger Ah capacity cells, not just talking cylindricals but pouches, hard-case prismatics, where 100-400Ah per cells are routine.